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https://dev.mysql.com/doc/refman/8.4/en/sql-statements.html | <div id="docs-body">
<div class="chapter">
<div class="titlepage">
<div>
<div>
<h1 class="title">
<a name="sql-statements">
</a>
Chapter 15 SQL Statements
</h1>
</div>
</div>
</div>
<div class="toc">
<p>
<b>
Table of Contents
</b>
</p>
<dl class="toc">
<dt>
<span class="section">
<a href="sql-data-definition-statements.html">
15.1 Data Definition Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="atomic-ddl.html">
15.1.1 Atomic Data Definition Statement Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-database.html">
15.1.2 ALTER DATABASE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-event.html">
15.1.3 ALTER EVENT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-function.html">
15.1.4 ALTER FUNCTION Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-instance.html">
15.1.5 ALTER INSTANCE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-logfile-group.html">
15.1.6 ALTER LOGFILE GROUP Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-procedure.html">
15.1.7 ALTER PROCEDURE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-server.html">
15.1.8 ALTER SERVER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-table.html">
15.1.9 ALTER TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-tablespace.html">
15.1.10 ALTER TABLESPACE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-view.html">
15.1.11 ALTER VIEW Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-database.html">
15.1.12 CREATE DATABASE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-event.html">
15.1.13 CREATE EVENT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-function.html">
15.1.14 CREATE FUNCTION Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-index.html">
15.1.15 CREATE INDEX Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-logfile-group.html">
15.1.16 CREATE LOGFILE GROUP Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-procedure.html">
15.1.17 CREATE PROCEDURE and CREATE FUNCTION Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-server.html">
15.1.18 CREATE SERVER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-spatial-reference-system.html">
15.1.19 CREATE SPATIAL REFERENCE SYSTEM Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-table.html">
15.1.20 CREATE TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-tablespace.html">
15.1.21 CREATE TABLESPACE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-trigger.html">
15.1.22 CREATE TRIGGER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="create-view.html">
15.1.23 CREATE VIEW Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-database.html">
15.1.24 DROP DATABASE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-event.html">
15.1.25 DROP EVENT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-function.html">
15.1.26 DROP FUNCTION Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-index.html">
15.1.27 DROP INDEX Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-logfile-group.html">
15.1.28 DROP LOGFILE GROUP Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-procedure.html">
15.1.29 DROP PROCEDURE and DROP FUNCTION Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-server.html">
15.1.30 DROP SERVER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-spatial-reference-system.html">
15.1.31 DROP SPATIAL REFERENCE SYSTEM Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-table.html">
15.1.32 DROP TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-tablespace.html">
15.1.33 DROP TABLESPACE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-trigger.html">
15.1.34 DROP TRIGGER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-view.html">
15.1.35 DROP VIEW Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="rename-table.html">
15.1.36 RENAME TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="truncate-table.html">
15.1.37 TRUNCATE TABLE Statement
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-data-manipulation-statements.html">
15.2 Data Manipulation Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="call.html">
15.2.1 CALL Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="delete.html">
15.2.2 DELETE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="do.html">
15.2.3 DO Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="except.html">
15.2.4 EXCEPT Clause
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="handler.html">
15.2.5 HANDLER Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="import-table.html">
15.2.6 IMPORT TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="insert.html">
15.2.7 INSERT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="intersect.html">
15.2.8 INTERSECT Clause
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="load-data.html">
15.2.9 LOAD DATA Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="load-xml.html">
15.2.10 LOAD XML Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="parenthesized-query-expressions.html">
15.2.11 Parenthesized Query Expressions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replace.html">
15.2.12 REPLACE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="select.html">
15.2.13 SELECT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="set-operations.html">
15.2.14 Set Operations with UNION, INTERSECT, and EXCEPT
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="subqueries.html">
15.2.15 Subqueries
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="table.html">
15.2.16 TABLE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="update.html">
15.2.17 UPDATE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="union.html">
15.2.18 UNION Clause
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="values.html">
15.2.19 VALUES Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="with.html">
15.2.20 WITH (Common Table Expressions)
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-transactional-statements.html">
15.3 Transactional and Locking Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="commit.html">
15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="cannot-roll-back.html">
15.3.2 Statements That Cannot Be Rolled Back
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="implicit-commit.html">
15.3.3 Statements That Cause an Implicit Commit
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="savepoint.html">
15.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="lock-instance-for-backup.html">
15.3.5 LOCK INSTANCE FOR BACKUP and UNLOCK INSTANCE Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="lock-tables.html">
15.3.6 LOCK TABLES and UNLOCK TABLES Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="set-transaction.html">
15.3.7 SET TRANSACTION Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="xa.html">
15.3.8 XA Transactions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-replication-statements.html">
15.4 Replication Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="replication-statements-source.html">
15.4.1 SQL Statements for Controlling Source Servers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-statements-replica.html">
15.4.2 SQL Statements for Controlling Replica Servers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="replication-statements-group.html">
15.4.3 SQL Statements for Controlling Group Replication
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-prepared-statements.html">
15.5 Prepared Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="prepare.html">
15.5.1 PREPARE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="execute.html">
15.5.2 EXECUTE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="deallocate-prepare.html">
15.5.3 DEALLOCATE PREPARE Statement
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-compound-statements.html">
15.6 Compound Statement Syntax
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="begin-end.html">
15.6.1 BEGIN ... END Compound Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="statement-labels.html">
15.6.2 Statement Labels
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="declare.html">
15.6.3 DECLARE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="stored-program-variables.html">
15.6.4 Variables in Stored Programs
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="flow-control-statements.html">
15.6.5 Flow Control Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="cursors.html">
15.6.6 Cursors
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="condition-handling.html">
15.6.7 Condition Handling
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="condition-handling-restrictions.html">
15.6.8 Restrictions on Condition Handling
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-server-administration-statements.html">
15.7 Database Administration Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="account-management-statements.html">
15.7.1 Account Management Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="resource-group-statements.html">
15.7.2 Resource Group Management Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="table-maintenance-statements.html">
15.7.3 Table Maintenance Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="component-statements.html">
15.7.4 Component, Plugin, and Loadable Function Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="clone.html">
15.7.5 CLONE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="set-statement.html">
15.7.6 SET Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="show.html">
15.7.7 SHOW Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="other-administrative-statements.html">
15.7.8 Other Administrative Statements
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="sql-utility-statements.html">
15.8 Utility Statements
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="describe.html">
15.8.1 DESCRIBE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="explain.html">
15.8.2 EXPLAIN Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="help.html">
15.8.3 HELP Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="use.html">
15.8.4 USE Statement
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</div>
<p>
This chapter describes the syntax for the
<a class="link" href="glossary.html#glos_sql" title="SQL">
SQL
</a>
statements supported by MySQL.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-features-mysqldb.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-features-mysqldb">
</a>
19.5.1.22 Replication of the mysql System Schema
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045135275776">
</a>
<a class="indexterm" name="idm46045135274272">
</a>
<a class="indexterm" name="idm46045135272784">
</a>
<a class="indexterm" name="idm46045135271296">
</a>
<p>
Data modification statements made to tables in the
<code class="literal">
mysql
</code>
schema are replicated according to the
value of
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
; if this
value is
<code class="literal">
MIXED
</code>
, these statements are
replicated using row-based format. However, statements that
would normally update this information indirectly—such
<a class="link" href="grant.html" title="15.7.1.6 GRANT Statement">
<code class="literal">
GRANT
</code>
</a>
,
<a class="link" href="revoke.html" title="15.7.1.8 REVOKE Statement">
<code class="literal">
REVOKE
</code>
</a>
, and statements
manipulating triggers, stored routines, and views—are
replicated to replicas using statement-based replication.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/password-management.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="password-management">
</a>
8.2.15 Password Management
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045248689824">
</a>
<p>
MySQL supports these password-management capabilities:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Password expiration, to require passwords to be changed
periodically.
</p>
</li>
<li class="listitem">
<p>
Password reuse restrictions, to prevent old passwords from
being chosen again.
</p>
</li>
<li class="listitem">
<p>
Password verification, to require that password changes also
specify the current password to be replaced.
</p>
</li>
<li class="listitem">
<p>
Dual passwords, to enable clients to connect using either a
primary or secondary password.
</p>
</li>
<li class="listitem">
<p>
Password strength assessment, to require strong passwords.
</p>
</li>
<li class="listitem">
<p>
Random password generation, as an alternative to requiring
explicit administrator-specified literal passwords.
</p>
</li>
<li class="listitem">
<p>
Password failure tracking, to enable temporary account locking
after too many consecutive incorrect-password login failures.
</p>
</li>
</ul>
</div>
<p>
The following sections describe these capabilities, except
password strength assessment, which is implemented using the
<code class="literal">
validate_password
</code>
component and is described in
<a class="xref" href="validate-password.html" title="8.4.3 The Password Validation Component">
Section 8.4.3, “The Password Validation Component”
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="password-management.html#internal-versus-external-credentials" title="Internal Versus External Credentials Storage">
Internal Versus External Credentials Storage
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="password-management.html#password-expiration-policy" title="Password Expiration Policy">
Password Expiration Policy
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="password-management.html#password-reuse-policy" title="Password Reuse Policy">
Password Reuse Policy
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="password-management.html#password-reverification-policy" title="Password Verification-Required Policy">
Password Verification-Required Policy
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="password-management.html#dual-passwords" title="Dual Password Support">
Dual Password Support
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="password-management.html#random-password-generation" title="Random Password Generation">
Random Password Generation
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="password-management.html#failed-login-tracking" title="Failed-Login Tracking and Temporary Account Locking">
Failed-Login Tracking and Temporary Account Locking
</a>
</p>
</li>
</ul>
</div>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
MySQL implements password-management capabilities using tables
in the
<code class="literal">
mysql
</code>
system database. If you upgrade
MySQL from an earlier version, your system tables might not be
up to date. In that case, the server writes messages similar to
these to the error log during the startup process (the exact
numbers may vary):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa66066346"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">[ERROR] Column count of mysql.user is wrong. Expected
49, found 47. The table is probably corrupted
[Warning] ACL table mysql.password_history missing.
Some operations may fail.</code></pre>
</div>
<p>
To correct the issue, perform the MySQL upgrade procedure. See
<a class="xref" href="upgrading.html" title="Chapter 3 Upgrading MySQL">
Chapter 3,
<i>
Upgrading MySQL
</i>
</a>
. Until this is done,
<span class="emphasis">
<em>
password changes are not possible.
</em>
</span>
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="internal-versus-external-credentials">
</a>
Internal Versus External Credentials Storage
</h4>
</div>
</div>
</div>
<p>
Some authentication plugins store account credentials internally
to MySQL, in the
<code class="literal">
mysql.user
</code>
system table:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
caching_sha2_password
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
mysql_native_password
</code>
(deprecated)
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
sha256_password
</code>
(deprecated)
</p>
</li>
</ul>
</div>
<p>
Most discussion in this section applies to such authentication
plugins because most password-management capabilities described
here are based on internal credentials storage handled by MySQL
itself. Other authentication plugins store account credentials
externally to MySQL. For accounts that use plugins that perform
authentication against an external credentials system, password
management must be handled externally against that system as
well.
</p>
<p>
The exception is that the options for failed-login tracking and
temporary account locking apply to all accounts, not just
accounts that use internal credentials storage, because MySQL is
able to assess the status of login attempts for any account no
matter whether it uses internal or external credentials storage.
</p>
<p>
For information about individual authentication plugins, see
<a class="xref" href="authentication-plugins.html" title="8.4.1 Authentication Plugins">
Section 8.4.1, “Authentication Plugins”
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="password-expiration-policy">
</a>
Password Expiration Policy
</h4>
</div>
</div>
</div>
<p>
MySQL enables database administrators to expire account
passwords manually, and to establish a policy for automatic
password expiration. Expiration policy can be established
globally, and individual accounts can be set to either defer to
the global policy or override the global policy with specific
per-account behavior.
</p>
<p>
To expire an account password manually, use the
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa36137687"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This operation marks the password expired in the corresponding
row in the
<code class="literal">
mysql.user
</code>
system table.
</p>
<p>
Password expiration according to policy is automatic and is
based on password age, which for a given account is assessed
from the date and time of its most recent password change. The
<code class="literal">
mysql.user
</code>
system table indicates for each
account when its password was last changed, and the server
automatically treats the password as expired at client
connection time if its age is greater than its permitted
lifetime. This works with no explicit manual password
expiration.
</p>
<p>
To establish automatic password-expiration policy globally, use
the
<a class="link" href="server-system-variables.html#sysvar_default_password_lifetime">
<code class="literal">
default_password_lifetime
</code>
</a>
system variable. Its default value is 0, which disables
automatic password expiration. If the value of
<a class="link" href="server-system-variables.html#sysvar_default_password_lifetime">
<code class="literal">
default_password_lifetime
</code>
</a>
is a
positive integer
<em class="replaceable">
<code>
N
</code>
</em>
, it indicates the
permitted password lifetime, such that passwords must be changed
every
<em class="replaceable">
<code>
N
</code>
</em>
days.
</p>
<p>
Examples:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
To establish a global policy that passwords have a lifetime
of approximately six months, start the server with these
lines in a server
<code class="filename">
my.cnf
</code>
file:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa58424907"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">default_password_lifetime</span><span class="token attr-value"><span class="token punctuation">=</span>180</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
To establish a global policy such that passwords never
expire, set
<a class="link" href="server-system-variables.html#sysvar_default_password_lifetime">
<code class="literal">
default_password_lifetime
</code>
</a>
to 0:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa18266153"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">default_password_lifetime</span><span class="token attr-value"><span class="token punctuation">=</span>0</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<a class="link" href="server-system-variables.html#sysvar_default_password_lifetime">
<code class="literal">
default_password_lifetime
</code>
</a>
can also be set and persisted at runtime:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa21654613"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">PERSIST</span> default_password_lifetime <span class="token operator">=</span> <span class="token number">180</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">PERSIST</span> default_password_lifetime <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
PERSIST
</code>
</a>
sets a value for the running MySQL
instance. It also saves the value to carry over to
subsequent server restarts; see
<a class="xref" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
Section 15.7.6.1, “SET Syntax for Variable Assignment”
</a>
. To change the value for the
running MySQL instance without having it carry over to
subsequent restarts, use the
<code class="literal">
GLOBAL
</code>
keyword rather than
<code class="literal">
PERSIST
</code>
.
</p>
</li>
</ul>
</div>
<p>
The global password-expiration policy applies to all accounts
that have not been set to override it. To establish policy for
individual accounts, use the
<code class="literal">
PASSWORD EXPIRE
</code>
option of the
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
and
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
statements. See
<a class="xref" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
Section 15.7.1.3, “CREATE USER Statement”
</a>
, and
<a class="xref" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
Section 15.7.1.1, “ALTER USER Statement”
</a>
.
</p>
<p>
Example account-specific statements:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Require the password to be changed every 90 days:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa45495337"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span> <span class="token keyword">INTERVAL</span> <span class="token number">90</span> <span class="token keyword">DAY</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span> <span class="token keyword">INTERVAL</span> <span class="token number">90</span> <span class="token keyword">DAY</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This expiration option overrides the global policy for all
accounts named by the statement.
</p>
</li>
<li class="listitem">
<p>
Disable password expiration:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa66608953"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span> <span class="token keyword">NEVER</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span> <span class="token keyword">NEVER</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This expiration option overrides the global policy for all
accounts named by the statement.
</p>
</li>
<li class="listitem">
<p>
Defer to the global expiration policy for all accounts named
by the statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa33743257"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span> <span class="token keyword">DEFAULT</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span> <span class="token keyword">DEFAULT</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
When a client successfully connects, the server determines
whether the account password has expired:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The server checks whether the password has been manually
expired.
</p>
</li>
<li class="listitem">
<p>
Otherwise, the server checks whether the password age is
greater than its permitted lifetime according to the
automatic password expiration policy. If so, the server
considers the password expired.
</p>
</li>
</ul>
</div>
<p>
If the password is expired (whether manually or automatically),
the server either disconnects the client or restricts the
operations permitted to it (see
<a class="xref" href="expired-password-handling.html" title="8.2.16 Server Handling of Expired Passwords">
Section 8.2.16, “Server Handling of Expired Passwords”
</a>
). Operations
performed by a restricted client result in an error until the
user establishes a new account password:
</p>
<a class="indexterm" name="idm46045248615248">
</a>
<a class="indexterm" name="idm46045248614208">
</a>
<a class="indexterm" name="idm46045248612720">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa87304117"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1820 (HY000)<span class="token punctuation">:</span> You must reset your password using ALTER USER
statement before executing this statement.
</span>
<span class="token prompt">mysql></span> <span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token function">USER</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">password</em>'</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.01 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
After the client resets the password, the server restores normal
access for the session, as well as for subsequent connections
that use the account. It is also possible for an administrative
user to reset the account password, but any existing restricted
sessions for that account remain restricted. A client using the
account must disconnect and reconnect before statements can be
executed successfully.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Although it is possible to
<span class="quote">
“
<span class="quote">
reset
</span>
”
</span>
an expired
password by setting it to its current value, it is preferable,
as a matter of good policy, to choose a different password.
DBAs can enforce non-reuse by establishing an appropriate
password-reuse policy. See
<a class="xref" href="password-management.html#password-reuse-policy" title="Password Reuse Policy">
Password Reuse Policy
</a>
.
</p>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="password-reuse-policy">
</a>
Password Reuse Policy
</h4>
</div>
</div>
</div>
<p>
MySQL enables restrictions to be placed on reuse of previous
passwords. Reuse restrictions can be established based on number
of password changes, time elapsed, or both. Reuse policy can be
established globally, and individual accounts can be set to
either defer to the global policy or override the global policy
with specific per-account behavior.
</p>
<p>
The password history for an account consists of passwords it has
been assigned in the past. MySQL can restrict new passwords from
being chosen from this history:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If an account is restricted on the basis of number of
password changes, a new password cannot be chosen from a
specified number of the most recent passwords. For example,
if the minimum number of password changes is set to 3, a new
password cannot be the same as any of the most recent 3
passwords.
</p>
</li>
<li class="listitem">
<p>
If an account is restricted based on time elapsed, a new
password cannot be chosen from passwords in the history that
are newer than a specified number of days. For example, if
the password reuse interval is set to 60, a new password
must not be among those previously chosen within the last 60
days.
</p>
</li>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The empty password does not count in the password history and
is subject to reuse at any time.
</p>
</div>
<p>
To establish password-reuse policy globally, use the
<a class="link" href="server-system-variables.html#sysvar_password_history">
<code class="literal">
password_history
</code>
</a>
and
<a class="link" href="server-system-variables.html#sysvar_password_reuse_interval">
<code class="literal">
password_reuse_interval
</code>
</a>
system
variables.
</p>
<p>
Examples:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
To prohibit reusing any of the last 6 passwords or passwords
newer than 365 days, put these lines in the server
<code class="filename">
my.cnf
</code>
file:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa46198965"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">password_history</span><span class="token attr-value"><span class="token punctuation">=</span>6</span>
<span class="token constant">password_reuse_interval</span><span class="token attr-value"><span class="token punctuation">=</span>365</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
To set and persist the variables at runtime, use statements
like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa25580274"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini">SET PERSIST password_history <span class="token attr-value"><span class="token punctuation">=</span> 6;</span>
SET PERSIST password_reuse_interval <span class="token attr-value"><span class="token punctuation">=</span> 365;</span></code></pre>
</div>
<p>
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
PERSIST
</code>
</a>
sets a value for the running MySQL
instance. It also saves the value to carry over to
subsequent server restarts; see
<a class="xref" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
Section 15.7.6.1, “SET Syntax for Variable Assignment”
</a>
. To change the value for the
running MySQL instance without having it carry over to
subsequent restarts, use the
<code class="literal">
GLOBAL
</code>
keyword rather than
<code class="literal">
PERSIST
</code>
.
</p>
</li>
</ul>
</div>
<p>
The global password-reuse policy applies to all accounts that
have not been set to override it. To establish policy for
individual accounts, use the
<code class="literal">
PASSWORD HISTORY
</code>
and
<code class="literal">
PASSWORD REUSE INTERVAL
</code>
options of the
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
and
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
statements. See
<a class="xref" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
Section 15.7.1.3, “CREATE USER Statement”
</a>
, and
<a class="xref" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
Section 15.7.1.1, “ALTER USER Statement”
</a>
.
</p>
<p>
Example account-specific statements:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Require a minimum of 5 password changes before permitting
reuse:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa25412577"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">HISTORY</span> <span class="token number">5</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">HISTORY</span> <span class="token number">5</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This history-length option overrides the global policy for
all accounts named by the statement.
</p>
</li>
<li class="listitem">
<p>
Require a minimum of 365 days elapsed before permitting
reuse:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75558374"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REUSE</span> <span class="token keyword">INTERVAL</span> <span class="token number">365</span> <span class="token keyword">DAY</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REUSE</span> <span class="token keyword">INTERVAL</span> <span class="token number">365</span> <span class="token keyword">DAY</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This time-elapsed option overrides the global policy for all
accounts named by the statement.
</p>
</li>
<li class="listitem">
<p>
To combine both types of reuse restrictions, use
<code class="literal">
PASSWORD HISTORY
</code>
and
<code class="literal">
PASSWORD
REUSE INTERVAL
</code>
together:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa86972695"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">PASSWORD</span> <span class="token keyword">HISTORY</span> <span class="token number">5</span>
<span class="token keyword">PASSWORD</span> <span class="token keyword">REUSE</span> <span class="token keyword">INTERVAL</span> <span class="token number">365</span> <span class="token keyword">DAY</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">PASSWORD</span> <span class="token keyword">HISTORY</span> <span class="token number">5</span>
<span class="token keyword">PASSWORD</span> <span class="token keyword">REUSE</span> <span class="token keyword">INTERVAL</span> <span class="token number">365</span> <span class="token keyword">DAY</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
These options override both global policy reuse restrictions
for all accounts named by the statement.
</p>
</li>
<li class="listitem">
<p>
Defer to the global policy for both types of reuse
restrictions:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa73213764"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">PASSWORD</span> <span class="token keyword">HISTORY</span> <span class="token keyword">DEFAULT</span>
<span class="token keyword">PASSWORD</span> <span class="token keyword">REUSE</span> <span class="token keyword">INTERVAL</span> <span class="token keyword">DEFAULT</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">PASSWORD</span> <span class="token keyword">HISTORY</span> <span class="token keyword">DEFAULT</span>
<span class="token keyword">PASSWORD</span> <span class="token keyword">REUSE</span> <span class="token keyword">INTERVAL</span> <span class="token keyword">DEFAULT</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="password-reverification-policy">
</a>
Password Verification-Required Policy
</h4>
</div>
</div>
</div>
<p>
It is possible to require that attempts to change an account
password be verified by specifying the current password to be
replaced. This enables DBAs to prevent users from changing a
password without proving that they know the current password.
Such changes could otherwise occur, for example, if one user
walks away from a terminal session temporarily without logging
out, and a malicious user uses the session to change the
original user's MySQL password. This can have unfortunate
consequences:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The original user becomes unable to access MySQL until the
account password is reset by an administrator.
</p>
</li>
<li class="listitem">
<p>
Until the password reset occurs, the malicious user can
access MySQL with the benign user's changed credentials.
</p>
</li>
</ul>
</div>
<p>
Password-verification policy can be established globally, and
individual accounts can be set to either defer to the global
policy or override the global policy with specific per-account
behavior.
</p>
<p>
For each account, its
<code class="literal">
mysql.user
</code>
row
indicates whether there is an account-specific setting requiring
verification of the current password for password change
attempts. The setting is established by the
<code class="literal">
PASSWORD
REQUIRE
</code>
option of the
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE
USER
</code>
</a>
and
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
statements:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If the account setting is
<code class="literal">
PASSWORD REQUIRE
CURRENT
</code>
, password changes must specify the current
password.
</p>
</li>
<li class="listitem">
<p>
If the account setting is
<code class="literal">
PASSWORD REQUIRE CURRENT
OPTIONAL
</code>
, password changes may but need not
specify the current password.
</p>
</li>
<li class="listitem">
<p>
If the account setting is
<code class="literal">
PASSWORD REQUIRE CURRENT
DEFAULT
</code>
, the
<a class="link" href="server-system-variables.html#sysvar_password_require_current">
<code class="literal">
password_require_current
</code>
</a>
system variable determines the verification-required policy
for the account:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If
<a class="link" href="server-system-variables.html#sysvar_password_require_current">
<code class="literal">
password_require_current
</code>
</a>
is enabled, password changes must specify the current
password.
</p>
</li>
<li class="listitem">
<p>
If
<a class="link" href="server-system-variables.html#sysvar_password_require_current">
<code class="literal">
password_require_current
</code>
</a>
is disabled, password changes may but need not specify
the current password.
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
<p>
In other words, if the account setting is not
<code class="literal">
PASSWORD
REQUIRE CURRENT DEFAULT
</code>
, the account setting takes
precedence over the global policy established by the
<a class="link" href="server-system-variables.html#sysvar_password_require_current">
<code class="literal">
password_require_current
</code>
</a>
system
variable. Otherwise, the account defers to the
<a class="link" href="server-system-variables.html#sysvar_password_require_current">
<code class="literal">
password_require_current
</code>
</a>
setting.
</p>
<p>
By default, password verification is optional:
<a class="link" href="server-system-variables.html#sysvar_password_require_current">
<code class="literal">
password_require_current
</code>
</a>
is
disabled and accounts created with no
<code class="literal">
PASSWORD
REQUIRE
</code>
option default to
<code class="literal">
PASSWORD REQUIRE
CURRENT DEFAULT
</code>
.
</p>
<p>
The following table shows how per-account settings interact with
<a class="link" href="server-system-variables.html#sysvar_password_require_current">
<code class="literal">
password_require_current
</code>
</a>
system
variable values to determine account password
verification-required policy.
</p>
<div class="table">
<a name="password-verification-policy-table">
</a>
<p class="title">
<b>
Table 8.10 Password-Verification Policy
</b>
</p>
<div class="table-contents">
<table summary="Interaction of mysql.user table and password_require_current system variable for password-verification policy.">
<colgroup>
<col style="width: 40%"/>
<col style="width: 30%"/>
<col style="width: 30%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Per-Account Setting
</th>
<th scope="col">
password_require_current System Variable
</th>
<th scope="col">
Password Changes Require Current Password?
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
PASSWORD REQUIRE CURRENT
</code>
</th>
<td>
<code class="literal">
OFF
</code>
</td>
<td>
Yes
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
PASSWORD REQUIRE CURRENT
</code>
</th>
<td>
<code class="literal">
ON
</code>
</td>
<td>
Yes
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
PASSWORD REQUIRE CURRENT OPTIONAL
</code>
</th>
<td>
<code class="literal">
OFF
</code>
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
PASSWORD REQUIRE CURRENT OPTIONAL
</code>
</th>
<td>
<code class="literal">
ON
</code>
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
PASSWORD REQUIRE CURRENT DEFAULT
</code>
</th>
<td>
<code class="literal">
OFF
</code>
</td>
<td>
No
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
PASSWORD REQUIRE CURRENT DEFAULT
</code>
</th>
<td>
<code class="literal">
ON
</code>
</td>
<td>
Yes
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Privileged users can change any account password without
specifying the current password, regardless of the
verification-required policy. A privileged user is one who has
the global
<a class="link" href="privileges-provided.html#priv_create-user">
<code class="literal">
CREATE USER
</code>
</a>
privilege or the
<a class="link" href="privileges-provided.html#priv_update">
<code class="literal">
UPDATE
</code>
</a>
privilege for the
<code class="literal">
mysql
</code>
system database.
</p>
</div>
<p>
To establish password-verification policy globally, use the
<a class="link" href="server-system-variables.html#sysvar_password_require_current">
<code class="literal">
password_require_current
</code>
</a>
system
variable. Its default value is
<code class="literal">
OFF
</code>
, so it is
not required that account password changes specify the current
password.
</p>
<p>
Examples:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
To establish a global policy that password changes must
specify the current password, start the server with these
lines in a server
<code class="filename">
my.cnf
</code>
file:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa77462526"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">password_require_current</span><span class="token attr-value"><span class="token punctuation">=</span>ON</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
To set and persist
<a class="link" href="server-system-variables.html#sysvar_password_require_current">
<code class="literal">
password_require_current
</code>
</a>
at
runtime, use a statement such as one of these:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa25613991"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">PERSIST</span> password_require_current <span class="token operator">=</span> <span class="token keyword">ON</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">PERSIST</span> password_require_current <span class="token operator">=</span> <span class="token keyword">OFF</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
PERSIST
</code>
</a>
sets a value for the running MySQL
instance. It also saves the value to carry over to
subsequent server restarts; see
<a class="xref" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
Section 15.7.6.1, “SET Syntax for Variable Assignment”
</a>
. To change the value for the
running MySQL instance without having it carry over to
subsequent restarts, use the
<code class="literal">
GLOBAL
</code>
keyword rather than
<code class="literal">
PERSIST
</code>
.
</p>
</li>
</ul>
</div>
<p>
The global password verification-required policy applies to all
accounts that have not been set to override it. To establish
policy for individual accounts, use the
<code class="literal">
PASSWORD
REQUIRE
</code>
options of the
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE
USER
</code>
</a>
and
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
statements. See
<a class="xref" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
Section 15.7.1.3, “CREATE USER Statement”
</a>
, and
<a class="xref" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
Section 15.7.1.1, “ALTER USER Statement”
</a>
.
</p>
<p>
Example account-specific statements:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Require that password changes specify the current password:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa66191533"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">CURRENT</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">CURRENT</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This verification option overrides the global policy for all
accounts named by the statement.
</p>
</li>
<li class="listitem">
<p>
Do not require that password changes specify the current
password (the current password may but need not be given):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa68197266"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">CURRENT</span> <span class="token keyword">OPTIONAL</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">CURRENT</span> <span class="token keyword">OPTIONAL</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This verification option overrides the global policy for all
accounts named by the statement.
</p>
</li>
<li class="listitem">
<p>
Defer to the global password verification-required policy
for all accounts named by the statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa71463880"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">CURRENT</span> <span class="token keyword">DEFAULT</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">CURRENT</span> <span class="token keyword">DEFAULT</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
Verification of the current password comes into play when a user
changes a password using the
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER
USER
</code>
</a>
or
<a class="link" href="set-password.html" title="15.7.1.10 SET PASSWORD Statement">
<code class="literal">
SET PASSWORD
</code>
</a>
statement. The examples use
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER
USER
</code>
</a>
, which is preferred over
<a class="link" href="set-password.html" title="15.7.1.10 SET PASSWORD Statement">
<code class="literal">
SET
PASSWORD
</code>
</a>
, but the principles described here are the
same for both statements.
</p>
<p>
In password-change statements, a
<code class="literal">
REPLACE
</code>
clause specifies the current password to be replaced. Examples:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Change the current user's password:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa62807784"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token function">USER</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span> <span class="token keyword">REPLACE</span> <span class="token string">'<em class="replaceable">current_auth_string</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Change a named user's password:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa85829751"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span>
<span class="token keyword">REPLACE</span> <span class="token string">'<em class="replaceable">current_auth_string</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Change a named user's authentication plugin and password:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa46411606"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> caching_sha2_password <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span>
<span class="token keyword">REPLACE</span> <span class="token string">'<em class="replaceable">current_auth_string</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
The
<code class="literal">
REPLACE
</code>
clause works like this:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
REPLACE
</code>
must be given if password changes
for the account are required to specify the current
password, as verification that the user attempting to make
the change actually knows the current password.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
REPLACE
</code>
is optional if password changes
for the account may but need not specify the current
password.
</p>
</li>
<li class="listitem">
<p>
If
<code class="literal">
REPLACE
</code>
is specified, it must specify
the correct current password, or an error occurs. This is
true even if
<code class="literal">
REPLACE
</code>
is optional.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
REPLACE
</code>
can be specified only when
changing the account password for the current user. (This
means that in the examples just shown, the statements that
explicitly name the account for
<code class="literal">
jeffrey
</code>
fail unless the current user is
<code class="literal">
jeffrey
</code>
.)
This is true even if the change is attempted for another
user by a privileged user; however, such a user can change
any password without specifying
<code class="literal">
REPLACE
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
REPLACE
</code>
is omitted from the binary log to
avoid writing cleartext passwords to it.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="dual-passwords">
</a>
Dual Password Support
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045248445344">
</a>
<a class="indexterm" name="idm46045248443856">
</a>
<a class="indexterm" name="idm46045248442784">
</a>
<a class="indexterm" name="idm46045248441712">
</a>
<p>
User accounts are permitted to have dual passwords, designated
as primary and secondary passwords. Dual-password capability
makes it possible to seamlessly perform credential changes in
scenarios like this:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A system has a large number of MySQL servers, possibly
involving replication.
</p>
</li>
<li class="listitem">
<p>
Multiple applications connect to different MySQL servers.
</p>
</li>
<li class="listitem">
<p>
Periodic credential changes must be made to the account or
accounts used by the applications to connect to the servers.
</p>
</li>
</ul>
</div>
<p>
Consider how a credential change must be performed in the
preceding type of scenario when an account is permitted only a
single password. In this case, there must be close cooperation
in the timing of when the account password change is made and
propagated throughout all servers, and when all applications
that use the account are updated to use the new password. This
process may involve downtime during which servers or
applications are unavailable.
</p>
<p>
With dual passwords, credential changes can be made more easily,
in phases, without requiring close cooperation, and without
downtime:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
For each affected account, establish a new primary password
on the servers, retaining the current password as the
secondary password. This enables servers to recognize either
the primary or secondary password for each account, while
applications can continue to connect to the servers using
the same password as previously (which is now the secondary
password).
</p>
</li>
<li class="listitem">
<p>
After the password change has propagated to all servers,
modify applications that use any affected account to connect
using the account primary password.
</p>
</li>
<li class="listitem">
<p>
After all applications have been migrated from the secondary
passwords to the primary passwords, the secondary passwords
are no longer needed and can be discarded. After this change
has propagated to all servers, only the primary password for
each account can be used to connect. The credential change
is now complete.
</p>
</li>
</ol>
</div>
<p>
MySQL implements dual-password capability with syntax that saves
and discards secondary passwords:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The
<code class="literal">
RETAIN CURRENT PASSWORD
</code>
clause for
the
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
and
<a class="link" href="set-password.html" title="15.7.1.10 SET PASSWORD Statement">
<code class="literal">
SET PASSWORD
</code>
</a>
statements saves
an account current password as its secondary password when
you assign a new primary password.
</p>
</li>
<li class="listitem">
<p>
The
<code class="literal">
DISCARD OLD PASSWORD
</code>
clause for
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
discards an
account secondary password, leaving only the primary
password.
</p>
</li>
</ul>
</div>
<p>
Suppose that, for the previously described credential-change
scenario, an account named
<code class="literal">
'appuser1'@'host1.example.com'
</code>
is used by
applications to connect to servers, and that the account
password is to be changed from
<code class="literal">
'
<em class="replaceable">
<code>
password_a
</code>
</em>
'
</code>
to
<code class="literal">
'
<em class="replaceable">
<code>
password_b
</code>
</em>
'
</code>
.
</p>
<p>
To perform this change of credentials, use
<code class="literal">
ALTER
USER
</code>
as follows:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
On each server that is not a replica, establish
<code class="literal">
'
<em class="replaceable">
<code>
password_b
</code>
</em>
'
</code>
as the new
<code class="literal">
appuser1
</code>
primary password,
retaining the current password as the secondary password:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa95975821"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'appuser1'</span>@<span class="token string">'host1.example.com'</span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">password_b</em>'</span>
<span class="token keyword">RETAIN</span> <span class="token keyword">CURRENT</span> <span class="token keyword">PASSWORD</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Wait for the password change to replicate throughout the
system to all replicas.
</p>
</li>
<li class="listitem">
<p>
Modify each application that uses the
<code class="literal">
appuser1
</code>
account so that it connects to
the servers using a password of
<code class="literal">
'
<em class="replaceable">
<code>
password_b
</code>
</em>
'
</code>
rather than
<code class="literal">
'
<em class="replaceable">
<code>
password_a
</code>
</em>
'
</code>
.
</p>
</li>
<li class="listitem">
<p>
At this point, the secondary password is no longer needed.
On each server that is not a replica, discard the secondary
password:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa12645861"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'appuser1'</span>@<span class="token string">'host1.example.com'</span>
<span class="token keyword">DISCARD</span> <span class="token keyword">OLD</span> <span class="token keyword">PASSWORD</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
After the discard-password change has replicated to all
replicas, the credential change is complete.
</p>
</li>
</ol>
</div>
<p>
The
<code class="literal">
RETAIN CURRENT PASSWORD
</code>
and
<code class="literal">
DISCARD OLD PASSWORD
</code>
clauses have the
following effects:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
RETAIN CURRENT PASSWORD
</code>
retains an
account current password as its secondary password,
replacing any existing secondary password. The new password
becomes the primary password, but clients can use the
account to connect to the server using either the primary or
secondary password. (Exception: If the new password
specified by the
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
or
<a class="link" href="set-password.html" title="15.7.1.10 SET PASSWORD Statement">
<code class="literal">
SET PASSWORD
</code>
</a>
statement is
empty, the secondary password becomes empty as well, even if
<code class="literal">
RETAIN CURRENT PASSWORD
</code>
is given.)
</p>
</li>
<li class="listitem">
<p>
If you specify
<code class="literal">
RETAIN CURRENT PASSWORD
</code>
for an account that has an empty primary password, the
statement fails.
</p>
</li>
<li class="listitem">
<p>
If an account has a secondary password and you change its
primary password without specifying
<code class="literal">
RETAIN CURRENT
PASSWORD
</code>
, the secondary password remains
unchanged.
</p>
</li>
<li class="listitem">
<p>
For
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
, if you change
the authentication plugin assigned to the account, the
secondary password is discarded. If you change the
authentication plugin and also specify
<code class="literal">
RETAIN
CURRENT PASSWORD
</code>
, the statement fails.
</p>
</li>
<li class="listitem">
<p>
For
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
,
<code class="literal">
DISCARD OLD PASSWORD
</code>
discards the
secondary password, if one exists. The account retains only
its primary password, and clients can use the account to
connect to the server only with the primary password.
</p>
</li>
</ul>
</div>
<p>
Statements that modify secondary passwords require these
privileges:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The
<a class="link" href="privileges-provided.html#priv_application-password-admin">
<code class="literal">
APPLICATION_PASSWORD_ADMIN
</code>
</a>
privilege is required to use the
<code class="literal">
RETAIN CURRENT
PASSWORD
</code>
or
<code class="literal">
DISCARD OLD
PASSWORD
</code>
clause for
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER
USER
</code>
</a>
and
<a class="link" href="set-password.html" title="15.7.1.10 SET PASSWORD Statement">
<code class="literal">
SET
PASSWORD
</code>
</a>
statements that apply to your own
account. The privilege is required to manipulate your own
secondary password because most users require only one
password.
</p>
</li>
<li class="listitem">
<p>
If an account is to be permitted to manipulate secondary
passwords for all accounts, it should be granted the
<a class="link" href="privileges-provided.html#priv_create-user">
<code class="literal">
CREATE USER
</code>
</a>
privilege rather
than
<a class="link" href="privileges-provided.html#priv_application-password-admin">
<code class="literal">
APPLICATION_PASSWORD_ADMIN
</code>
</a>
.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="random-password-generation">
</a>
Random Password Generation
</h4>
</div>
</div>
</div>
<p>
The
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
,
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
, and
<a class="link" href="set-password.html" title="15.7.1.10 SET PASSWORD Statement">
<code class="literal">
SET PASSWORD
</code>
</a>
statements have the
capability of generating random passwords for user accounts, as
an alternative to requiring explicit administrator-specified
literal passwords. See the description of each statement for
details about the syntax. This section describes the
characteristics common to generated random passwords.
</p>
<p>
By default, generated random passwords have a length of 20
characters. This length is controlled by the
<a class="link" href="server-system-variables.html#sysvar_generated_random_password_length">
<code class="literal">
generated_random_password_length
</code>
</a>
system variable, which has a range from 5 to 255.
</p>
<p>
For each account for which a statement generates a random
password, the statement stores the password in the
<code class="literal">
mysql.user
</code>
system table, hashed appropriately
for the account authentication plugin. The statement also
returns the cleartext password in a row of a result set to make
it available to the user or application executing the statement.
The result set columns are named
<code class="literal">
user
</code>
,
<code class="literal">
host
</code>
,
<code class="literal">
generated password
</code>
,
and
<code class="literal">
auth_factor
</code>
indicating the user name and
host name values that identify the affected row in the
<code class="literal">
mysql.user
</code>
system table, the cleartext
generated password, and the authentication factor the displayed
password value applies to.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa48582610"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">USER</span>
<span class="token string">'u1'</span>@<span class="token string">'localhost'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span><span class="token punctuation">,</span>
<span class="token string">'u2'</span>@<span class="token string">'%.example.com'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span><span class="token punctuation">,</span>
<span class="token string">'u3'</span>@<span class="token string">'%.org'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> user <span class="token punctuation">|</span> host <span class="token punctuation">|</span> generated password <span class="token punctuation">|</span> auth_factor <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> u1 <span class="token punctuation">|</span> localhost <span class="token punctuation">|</span> iOeqf>Mh9:;XD&qn(Hl} <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> u2 <span class="token punctuation">|</span> %.example.com <span class="token punctuation">|</span> sXTSAEvw3St<span class="token punctuation">-</span>R<span class="token punctuation">+</span>_<span class="token punctuation">-</span>C3Vb <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> u3 <span class="token punctuation">|</span> %.org <span class="token punctuation">|</span> nEVe%Ctw/U/*Md)Exc7& <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">ALTER</span> <span class="token keyword">USER</span>
<span class="token string">'u1'</span>@<span class="token string">'localhost'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span><span class="token punctuation">,</span>
<span class="token string">'u2'</span>@<span class="token string">'%.example.com'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> user <span class="token punctuation">|</span> host <span class="token punctuation">|</span> generated password <span class="token punctuation">|</span> auth_factor <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> u1 <span class="token punctuation">|</span> localhost <span class="token punctuation">|</span> Seiei:&cw}8]@3OA64vh <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> u2 <span class="token punctuation">|</span> %.example.com <span class="token punctuation">|</span> j@&diTX80l8}(NiHXSae <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">FOR</span> <span class="token string">'u3'</span>@<span class="token string">'%.org'</span> <span class="token keyword">TO</span> <span class="token keyword">RANDOM</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> user <span class="token punctuation">|</span> host <span class="token punctuation">|</span> generated password <span class="token punctuation">|</span> auth_factor <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> u3 <span class="token punctuation">|</span> %.org <span class="token punctuation">|</span> n&cz2xF;P3!U)<span class="token punctuation">+</span>]Vw52H <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
A
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
,
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
, or
<a class="link" href="set-password.html" title="15.7.1.10 SET PASSWORD Statement">
<code class="literal">
SET PASSWORD
</code>
</a>
statement that
generates a random password for an account is written to the
binary log as a
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
or
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
statement with an
<code class="literal">
IDENTIFIED WITH
<em class="replaceable">
<code>
auth_plugin
</code>
</em>
AS '
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
, clause,
where
<em class="replaceable">
<code>
auth_plugin
</code>
</em>
is the account
authentication plugin and
<code class="literal">
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
is
the account hashed password value.
</p>
<p>
If the
<code class="literal">
validate_password
</code>
component is
installed, the policy that it implements has no effect on
generated passwords. (The purpose of password validation is to
help humans create better passwords.)
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="failed-login-tracking">
</a>
Failed-Login Tracking and Temporary Account Locking
</h4>
</div>
</div>
</div>
<p>
Administrators can configure user accounts such that too many
consecutive login failures cause temporary account locking.
</p>
<p>
<span class="quote">
“
<span class="quote">
Login failure
</span>
”
</span>
in this context means failure of
the client to provide a correct password during a connection
attempt. It does not include failure to connect for reasons such
as unknown user or network issues. For accounts that have dual
passwords (see
<a class="xref" href="password-management.html#dual-passwords" title="Dual Password Support">
Dual Password Support
</a>
), either account
password counts as correct.
</p>
<p>
The required number of login failures and the lock time are
configurable per account, using the
<code class="literal">
FAILED_LOGIN_ATTEMPTS
</code>
and
<code class="literal">
PASSWORD_LOCK_TIME
</code>
options of the
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
and
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
statements. Examples:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa23658352"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'u1'</span>@<span class="token string">'localhost'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">password</em>'</span>
<span class="token keyword">FAILED_LOGIN_ATTEMPTS</span> <span class="token number">3</span> <span class="token keyword">PASSWORD_LOCK_TIME</span> <span class="token number">3</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'u2'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">FAILED_LOGIN_ATTEMPTS</span> <span class="token number">4</span> <span class="token keyword">PASSWORD_LOCK_TIME</span> <span class="token keyword">UNBOUNDED</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
When too many consecutive login failures occur, the client
receives an error that looks like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa42755714"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">ERROR 3957 (HY000): Access denied for user <em class="replaceable">user</em>.
Account is blocked for <em class="replaceable">D</em> day(s) (<em class="replaceable">R</em> day(s) remaining)
due to <em class="replaceable">N</em> consecutive failed logins.</code></pre>
</div>
<p>
Use the options as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
FAILED_LOGIN_ATTEMPTS
<em class="replaceable">
<code>
N
</code>
</em>
</code>
</p>
<p>
This option indicates whether to track account login
attempts that specify an incorrect password. The number
<em class="replaceable">
<code>
N
</code>
</em>
specifies how many consecutive
incorrect passwords cause temporary account locking.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
PASSWORD_LOCK_TIME {
<em class="replaceable">
<code>
N
</code>
</em>
|
UNBOUNDED}
</code>
</p>
<p>
This option indicates how long to lock the account after too
many consecutive login attempts provide an incorrect
password. The value is a number
<em class="replaceable">
<code>
N
</code>
</em>
to specify the number of days the account remains locked, or
<code class="literal">
UNBOUNDED
</code>
to specify that when an account
enters the temporarily locked state, the duration of that
state is unbounded and does not end until the account is
unlocked. The conditions under which unlocking occurs are
described later.
</p>
</li>
</ul>
</div>
<p>
Permitted values of
<em class="replaceable">
<code>
N
</code>
</em>
for each option
are in the range from 0 to 32767. A value of 0 disables the
option.
</p>
<p>
Failed-login tracking and temporary account locking have these
characteristics:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
For failed-login tracking and temporary locking to occur for
an account, its
<code class="literal">
FAILED_LOGIN_ATTEMPTS
</code>
and
<code class="literal">
PASSWORD_LOCK_TIME
</code>
options both must be
nonzero.
</p>
</li>
<li class="listitem">
<p>
For
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
, if
<code class="literal">
FAILED_LOGIN_ATTEMPTS
</code>
or
<code class="literal">
PASSWORD_LOCK_TIME
</code>
is not specified, its
implicit default value is 0 for all accounts named by the
statement. This means that failed-login tracking and
temporary account locking are disabled.
</p>
</li>
<li class="listitem">
<p>
For
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
, if
<code class="literal">
FAILED_LOGIN_ATTEMPTS
</code>
or
<code class="literal">
PASSWORD_LOCK_TIME
</code>
is not specified, its
value remains unchanged for all accounts named by the
statement.
</p>
</li>
<li class="listitem">
<p>
For temporary account locking to occur, password failures
must be consecutive. Any successful login that occurs prior
to reaching the
<code class="literal">
FAILED_LOGIN_ATTEMPTS
</code>
value for failed logins causes failure counting to reset.
For example, if
<code class="literal">
FAILED_LOGIN_ATTEMPTS
</code>
is
4 and three consecutive password failures have occurred, one
more failure is necessary for locking to begin. But if the
next login succeeds, failed-login counting for the account
is reset so that four consecutive failures are again
required for locking.
</p>
</li>
<li class="listitem">
<p>
Once temporary locking begins, successful login cannot occur
even with the correct password until either the lock
duration has passed or the account is unlocked by one of the
account-reset methods listed in the following discussion.
</p>
</li>
</ul>
</div>
<p>
When the server reads the grant tables, it initializes state
information for each account regarding whether failed-login
tracking is enabled, whether the account is currently
temporarily locked and when locking began if so, and the number
of failures before temporary locking occurs if the account is
not locked.
</p>
<p>
An account's state information can be reset, which means that
failed-login counting is reset, and the account is unlocked if
currently temporarily locked. Account resets can be global for
all accounts or per account:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A global reset of all accounts occurs for any of these
conditions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
A server restart.
</p>
</li>
<li class="listitem">
<p>
Execution of
<a class="link" href="flush.html#flush-privileges">
<code class="literal">
FLUSH
PRIVILEGES
</code>
</a>
. (Starting the server with
<a class="link" href="server-options.html#option_mysqld_skip-grant-tables">
<code class="option">
--skip-grant-tables
</code>
</a>
causes the grant tables not to be read, which disables
failed-login tracking. In this case, the first execution
of
<a class="link" href="flush.html#flush-privileges">
<code class="literal">
FLUSH PRIVILEGES
</code>
</a>
causes the server to read the grant tables and enable
failed-login tracking, in addition to resetting all
accounts.)
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
A per-account reset occurs for any of these conditions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Successful login for the account.
</p>
</li>
<li class="listitem">
<p>
The lock duration passes. In this case, failed-login
counting resets at the time of the next login attempt.
</p>
</li>
<li class="listitem">
<p>
Execution of an
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER
USER
</code>
</a>
statement for the account that sets
either
<code class="literal">
FAILED_LOGIN_ATTEMPTS
</code>
or
<code class="literal">
PASSWORD_LOCK_TIME
</code>
(or both) to any
value (including the current option value), or execution
of an
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER
USER ... UNLOCK
</code>
</a>
statement for the account.
</p>
<p>
Other
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
statements for the account have no effect on its current
failed-login count or its locking state.
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
<p>
Failed-login tracking is tied to the login account that is used
to check credentials. If user proxying is in use, tracking
occurs for the proxy user, not the proxied user. That is,
tracking is tied to the account indicated by
<a class="link" href="information-functions.html#function_user">
<code class="literal">
USER()
</code>
</a>
, not the account indicated
by
<a class="link" href="information-functions.html#function_current-user">
<code class="literal">
CURRENT_USER()
</code>
</a>
. For
information about the distinction between proxy and proxied
users, see
<a class="xref" href="proxy-users.html" title="8.2.19 Proxy Users">
Section 8.2.19, “Proxy Users”
</a>
.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/indexes.html | <div id="docs-body">
<div class="appendix">
<div class="titlepage">
<div>
<div>
<h1 class="title">
<a name="indexes">
</a>
Appendix C Indexes
</h1>
</div>
</div>
</div>
<div class="toc">
<p>
<b>
Table of Contents
</b>
</p>
<dl class="toc">
<dt>
<span class="index">
<a href="ix01.html">
General Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-cfunc.html">
C Function Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-command.html">
Command Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-function.html">
Function Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-is.html">
INFORMATION_SCHEMA Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-jointype.html">
Join Types Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-operator.html">
Operator Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-option.html">
Option Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-priv.html">
Privileges Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-sqlmode.html">
SQL Modes Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-statement.html">
Statement/Syntax Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-statvar.html">
Status Variable Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-sysvar.html">
System Variable Index
</a>
</span>
</dt>
<dt>
<span class="index">
<a href="dynindex-isolevel.html">
Transaction Isolation Level Index
</a>
</span>
</dt>
</dl>
</div>
<p>
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/channels-startup-options.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="channels-startup-options">
</a>
19.2.2.3 Startup Options and Replication Channels
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045138112960">
</a>
<a class="indexterm" name="idm46045138111472">
</a>
<p>
This section describes startup options which are impacted by the
addition of replication channels.
</p>
<p>
The following startup options now affect
<span class="emphasis">
<em>
all
</em>
</span>
channels in a replication topology.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="literal">
--log-replica-updates
</code>
</a>
</p>
<p>
All transactions received by the replica (even from multiple
sources) are written in the binary log.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replication-options-replica.html#sysvar_relay_log_purge">
<code class="literal">
--relay-log-purge
</code>
</a>
</p>
<p>
When set, each channel purges its own relay log automatically.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replication-options-replica.html#sysvar_replica_transaction_retries">
<code class="literal">
--replica-transaction-retries
</code>
</a>
</p>
<p>
The specified number of transaction retries can take place on
all applier threads of all channels.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replication-options-replica.html#option_mysqld_skip-replica-start">
<code class="option">
--skip-replica-start
</code>
</a>
</p>
<p>
No replication threads start on any channels.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replication-options-replica.html#sysvar_replica_skip_errors">
<code class="literal">
--replica-skip-errors
</code>
</a>
</p>
<p>
Execution continues and errors are skipped for all channels.
</p>
</li>
</ul>
</div>
<p>
The values set for the following startup options apply on each
channel; since these are
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
startup
options, they are applied on every channel.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="option">
--max-relay-log-size=
<em class="replaceable">
<code>
size
</code>
</em>
</code>
</p>
<p>
Maximum size of the individual relay log file for each
channel; after reaching this limit, the file is rotated.
</p>
</li>
<li class="listitem">
<p>
<code class="option">
--relay-log-space-limit=
<em class="replaceable">
<code>
size
</code>
</em>
</code>
</p>
<p>
Upper limit for the total size of all relay logs combined, for
each individual channel. For
<em class="replaceable">
<code>
N
</code>
</em>
channels, the combined size of these logs is limited to
<a class="link" href="replication-options-replica.html#sysvar_relay_log_space_limit">
<code class="literal">
relay_log_space_limit *
<em class="replaceable">
<code>
N
</code>
</em>
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="option">
--replica-parallel-workers=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</p>
<p>
Number of replication applier threads per channel.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replication-options-replica.html#sysvar_replica_checkpoint_group">
<code class="literal">
replica_checkpoint_group
</code>
</a>
</p>
<p>
Waiting time by an receiver thread for each source.
</p>
</li>
<li class="listitem">
<p>
<code class="option">
--relay-log-index=filename
</code>
</p>
<p>
Base name for each channel's relay log index file. See
<a class="xref" href="channels-naming-conventions.html" title="19.2.2.4 Replication Channel Naming Conventions">
Section 19.2.2.4, “Replication Channel Naming Conventions”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="option">
--relay-log=filename
</code>
</p>
<p>
Denotes the base name of each channel's relay log file.
See
<a class="xref" href="channels-naming-conventions.html" title="19.2.2.4 Replication Channel Naming Conventions">
Section 19.2.2.4, “Replication Channel Naming Conventions”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="option">
--replica-net-timeout=
<em class="replaceable">
<code>
N
</code>
</em>
</code>
</p>
<p>
This value is set per channel, so that each channel waits for
<em class="replaceable">
<code>
N
</code>
</em>
seconds to check for a broken
connection.
</p>
</li>
<li class="listitem">
<p>
<code class="option">
--replica-skip-counter=
<em class="replaceable">
<code>
N
</code>
</em>
</code>
</p>
<p>
This value is set per channel, so that each channel skips
<em class="replaceable">
<code>
N
</code>
</em>
events from its source.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-host-summary-by-stages.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-host-summary-by-stages">
</a>
30.4.3.4 The host_summary_by_stages and x$host_summary_by_stages Views
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045063287408">
</a>
<a class="indexterm" name="idm46045063285952">
</a>
<a class="indexterm" name="idm46045063284448">
</a>
<a class="indexterm" name="idm46045063282944">
</a>
<p>
These views summarize statement stages, grouped by host. By
default, rows are sorted by host and descending total latency.
</p>
<p>
The
<a class="link" href="sys-host-summary-by-stages.html" title="30.4.3.4 The host_summary_by_stages and x$host_summary_by_stages Views">
<code class="literal">
host_summary_by_stages
</code>
</a>
and
<a class="link" href="sys-host-summary-by-stages.html" title="30.4.3.4 The host_summary_by_stages and x$host_summary_by_stages Views">
<code class="literal">
x$host_summary_by_stages
</code>
</a>
views
have these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
host
</code>
</p>
<p>
The host from which the client connected. Rows for which
the
<code class="literal">
HOST
</code>
column in the underlying
Performance Schema table is
<code class="literal">
NULL
</code>
are
assumed to be for background threads and are reported with
a host name of
<code class="literal">
background
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
event_name
</code>
</p>
<p>
The stage event name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
total
</code>
</p>
<p>
The total number of occurrences of the stage event for the
host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
total_latency
</code>
</p>
<p>
The total wait time of timed occurrences of the stage
event for the host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
avg_latency
</code>
</p>
<p>
The average wait time per timed occurrence of the stage
event for the host.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster.html | <div id="docs-body">
<div class="chapter">
<div class="titlepage">
<div>
<div>
<h1 class="title">
<a name="mysql-cluster">
</a>
Chapter 25 MySQL NDB Cluster 8.4
</h1>
</div>
</div>
</div>
<div class="toc">
<p>
<b>
Table of Contents
</b>
</p>
<dl class="toc">
<dt>
<span class="section">
<a href="mysql-cluster-general-info.html">
25.1 General Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-overview.html">
25.2 NDB Cluster Overview
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-basics.html">
25.2.1 NDB Cluster Core Concepts
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-nodes-groups.html">
25.2.2 NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-overview-requirements.html">
25.2.3 NDB Cluster Hardware, Software, and Networking Requirements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-what-is-new.html">
25.2.4 What is New in MySQL NDB Cluster 8.4
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-added-deprecated-removed.html">
25.2.5 Options, Variables, and Parameters Added, Deprecated or Removed in NDB
8.4
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-compared.html">
25.2.6 MySQL Server Using InnoDB Compared with NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations.html">
25.2.7 Known Limitations of NDB Cluster
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-installation.html">
25.3 NDB Cluster Installation
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-install-linux.html">
25.3.1 Installation of NDB Cluster on Linux
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-install-windows.html">
25.3.2 Installing NDB Cluster on Windows
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-install-configuration.html">
25.3.3 Initial Configuration of NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-install-first-start.html">
25.3.4 Initial Startup of NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-install-example-data.html">
25.3.5 NDB Cluster Example with Tables and Data
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-install-shutdown-restart.html">
25.3.6 Safe Shutdown and Restart of NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-upgrade-downgrade.html">
25.3.7 Upgrading and Downgrading NDB Cluster
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-configuration.html">
25.4 Configuration of NDB Cluster
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-quick.html">
25.4.1 Quick Test Setup of NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-configuration-overview.html">
25.4.2 Overview of NDB Cluster Configuration Parameters, Options, and Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-config-file.html">
25.4.3 NDB Cluster Configuration Files
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-interconnects.html">
25.4.4 Using High-Speed Interconnects with NDB Cluster
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-programs.html">
25.5 NDB Cluster Programs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndbd.html">
25.5.1 ndbd — The NDB Cluster Data Node Daemon
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndbinfo-select-all.html">
25.5.2 ndbinfo_select_all — Select From ndbinfo Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndbmtd.html">
25.5.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-mgmd.html">
25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-mgm.html">
25.5.5 ndb_mgm — The NDB Cluster Management Client
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-blob-tool.html">
25.5.6 ndb_blob_tool — Check and Repair BLOB and TEXT columns of NDB Cluster
Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-config.html">
25.5.7 ndb_config — Extract NDB Cluster Configuration Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-delete-all.html">
25.5.8 ndb_delete_all — Delete All Rows from an NDB Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-desc.html">
25.5.9 ndb_desc — Describe NDB Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-drop-index.html">
25.5.10 ndb_drop_index — Drop Index from an NDB Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-drop-table.html">
25.5.11 ndb_drop_table — Drop an NDB Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-error-reporter.html">
25.5.12 ndb_error_reporter — NDB Error-Reporting Utility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-import.html">
25.5.13 ndb_import — Import CSV Data Into NDB
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-index-stat.html">
25.5.14 ndb_index_stat — NDB Index Statistics Utility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-move-data.html">
25.5.15 ndb_move_data — NDB Data Copy Utility
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-perror.html">
25.5.16 ndb_perror — Obtain NDB Error Message Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-print-backup-file.html">
25.5.17 ndb_print_backup_file — Print NDB Backup File Contents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-print-file.html">
25.5.18 ndb_print_file — Print NDB Disk Data File Contents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-print-frag-file.html">
25.5.19 ndb_print_frag_file — Print NDB Fragment List File Contents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-print-schema-file.html">
25.5.20 ndb_print_schema_file — Print NDB Schema File Contents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-print-sys-file.html">
25.5.21 ndb_print_sys_file — Print NDB System File Contents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-redo-log-reader.html">
25.5.22 ndb_redo_log_reader — Check and Print Content of Cluster Redo Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-restore.html">
25.5.23 ndb_restore — Restore an NDB Cluster Backup
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-secretsfile-reader.html">
25.5.24 ndb_secretsfile_reader — Obtain Key Information from an Encrypted NDB
Data File
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-select-all.html">
25.5.25 ndb_select_all — Print Rows from an NDB Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-select-count.html">
25.5.26 ndb_select_count — Print Row Counts for NDB Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-show-tables.html">
25.5.27 ndb_show_tables — Display List of NDB Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-sign-keys.html">
25.5.28 ndb_sign_keys — Create, Sign, and Manage TLS Keys and Certificates for NDB
Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-size-pl.html">
25.5.29 ndb_size.pl — NDBCLUSTER Size Requirement Estimator
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-top.html">
25.5.30 ndb_top — View CPU usage information for NDB threads
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndb-waiter.html">
25.5.31 ndb_waiter — Wait for NDB Cluster to Reach a Given Status
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-programs-ndbxfrm.html">
25.5.32 ndbxfrm — Compress, Decompress, Encrypt, and Decrypt
Files Created by NDB Cluster
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-management.html">
25.6 Management of NDB Cluster
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-mgm-client-commands.html">
25.6.1 Commands in the NDB Cluster Management Client
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-logs-ndb-messages.html">
25.6.2 NDB Cluster Log Messages
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-event-reports.html">
25.6.3 Event Reports Generated in NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-start-phases.html">
25.6.4 Summary of NDB Cluster Start Phases
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-rolling-restart.html">
25.6.5 Performing a Rolling Restart of an NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-single-user-mode.html">
25.6.6 NDB Cluster Single User Mode
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-online-add-node.html">
25.6.7 Adding NDB Cluster Data Nodes Online
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-backup.html">
25.6.8 Online Backup of NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-importing-data.html">
25.6.9 Importing Data Into MySQL Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-mysqld.html">
25.6.10 MySQL Server Usage for NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-disk-data.html">
25.6.11 NDB Cluster Disk Data Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-online-operations.html">
25.6.12 Online Operations with ALTER TABLE in NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-privilege-synchronization.html">
25.6.13 Privilege Synchronization and NDB_STORED_USER
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-tde.html">
25.6.14 File System Encryption for NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-tls.html">
25.6.15 TLS Link Encryption for NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-ndb-api-statistics.html">
25.6.16 NDB API Statistics Counters and Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-ndbinfo.html">
25.6.17 ndbinfo: The NDB Cluster Information Database
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-information-schema-tables.html">
25.6.18 INFORMATION_SCHEMA Tables for NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-ps-tables.html">
25.6.19 NDB Cluster and the Performance Schema
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-sql-statements.html">
25.6.20 Quick Reference: NDB Cluster SQL Statements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-security.html">
25.6.21 NDB Cluster Security Issues
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-replication.html">
25.7 NDB Cluster Replication
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="mysql-cluster-replication-abbreviations.html">
25.7.1 NDB Cluster Replication: Abbreviations and Symbols
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-general.html">
25.7.2 General Requirements for NDB Cluster Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-issues.html">
25.7.3 Known Issues in NDB Cluster Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-schema.html">
25.7.4 NDB Cluster Replication Schema and Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-preparation.html">
25.7.5 Preparing the NDB Cluster for Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-starting.html">
25.7.6 Starting NDB Cluster Replication (Single Replication Channel)
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-two-channels.html">
25.7.7 Using Two Replication Channels for NDB Cluster Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-failover.html">
25.7.8 Implementing Failover with NDB Cluster Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-backups.html">
25.7.9 NDB Cluster Backups With NDB Cluster Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-multi-source.html">
25.7.10 NDB Cluster Replication: Bidirectional and Circular Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-mta.html">
25.7.11 NDB Cluster Replication Using the Multithreaded Applier
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-replication-conflict-resolution.html">
25.7.12 NDB Cluster Replication Conflict Resolution
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="mysql-cluster-news.html">
25.8 NDB Cluster Release Notes
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045124461648">
</a>
<a class="indexterm" name="idm46045124460576">
</a>
<a class="indexterm" name="idm46045124459088">
</a>
<a class="indexterm" name="idm46045124457584">
</a>
<p class="ndb-rel-level">
This chapter provides information about MySQL
<span class="firstterm">
NDB Cluster
</span>
, a
high-availability, high-redundancy version of MySQL adapted for the
distributed computing environment, as well as information specific
to NDB Cluster 8.4 (NDB 8.4.0), based on version
8.4 of the NDB storage engine. See
<a class="xref" href="mysql-cluster-what-is-new.html" title="25.2.4 What is New in MySQL NDB Cluster 8.4">
Section 25.2.4, “What is New in MySQL NDB Cluster 8.4”
</a>
, for information about
differences in NDB 8.4 as compared to earlier releases. See
<a class="ulink" href="/doc/refman/8.0/en/mysql-cluster.html" target="_top">
MySQL NDB Cluster 8.0
</a>
for information about NDB
Cluster 8.0. Both NDB 8.0 and NDB 8.4 are intended for use in
production environments. NDB Cluster 7.6 and 7.5 are previous GA
releases still supported in production, although new deployments can
and should use either of MySQL NDB Cluster 8.0 or 8.4.
</p>
<p>
<span class="emphasis">
<em>
NDB Cluster 7.4 and older release series are no longer
supported or maintained
</em>
</span>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysqlimport.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysqlimport">
</a>
6.5.5 mysqlimport — A Data Import Program
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045311955264">
</a>
<a class="indexterm" name="idm46045311954352">
</a>
<a class="indexterm" name="idm46045311952992">
</a>
<a class="indexterm" name="idm46045311951632">
</a>
<a class="indexterm" name="idm46045311950272">
</a>
<p>
The
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
client provides a
command-line interface to the
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD
DATA
</code>
</a>
SQL statement. Most options to
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
correspond directly to clauses of
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD DATA
</code>
</a>
syntax. See
<a class="xref" href="load-data.html" title="15.2.9 LOAD DATA Statement">
Section 15.2.9, “LOAD DATA Statement”
</a>
.
</p>
<p>
Invoke
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa98203679"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqlimport <span class="token punctuation">[</span><em class="replaceable">options</em><span class="token punctuation">]</span> <em class="replaceable">db_name</em> <em class="replaceable">textfile1</em> <span class="token punctuation">[</span><em class="replaceable">textfile2</em> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">]</span></code></pre>
</div>
<p>
For each text file named on the command line,
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
strips any extension from the
file name and uses the result to determine the name of the table
into which to import the file's contents. For example, files
named
<code class="filename">
patient.txt
</code>
,
<code class="filename">
patient.text
</code>
, and
<code class="filename">
patient
</code>
all would be imported into a table
named
<code class="literal">
patient
</code>
.
</p>
<p>
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
supports the following options,
which can be specified on the command line or in the
<code class="literal">
[mysqlimport]
</code>
and
<code class="literal">
[client]
</code>
groups of an option file. For information about option files
used by MySQL programs, see
<a class="xref" href="option-files.html" title="6.2.2.2 Using Option Files">
Section 6.2.2.2, “Using Option Files”
</a>
.
</p>
<div class="table">
<a name="idm46045311929664">
</a>
<p class="title">
<b>
Table 6.14 mysqlimport Options
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="Command-line options available for mysqlimport.">
<colgroup>
<col style="width: 35%"/>
<col style="width: 64%"/>
</colgroup>
<thead>
<tr>
<th>
Option Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_bind-address">
--bind-address
</a>
</td>
<td>
Use specified network interface to connect to MySQL Server
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_character-sets-dir">
--character-sets-dir
</a>
</td>
<td>
Directory where character sets can be found
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_columns">
--columns
</a>
</td>
<td>
This option takes a comma-separated list of column names as its value
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_compress">
--compress
</a>
</td>
<td>
Compress all information sent between client and server
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_compression-algorithms">
--compression-algorithms
</a>
</td>
<td>
Permitted compression algorithms for connections to server
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_debug">
--debug
</a>
</td>
<td>
Write debugging log
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_debug-check">
--debug-check
</a>
</td>
<td>
Print debugging information when program exits
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_debug-info">
--debug-info
</a>
</td>
<td>
Print debugging information, memory, and CPU statistics when program exits
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_default-auth">
--default-auth
</a>
</td>
<td>
Authentication plugin to use
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_default-character-set">
--default-character-set
</a>
</td>
<td>
Specify default character set
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_defaults-extra-file">
--defaults-extra-file
</a>
</td>
<td>
Read named option file in addition to usual option files
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_defaults-file">
--defaults-file
</a>
</td>
<td>
Read only named option file
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_defaults-group-suffix">
--defaults-group-suffix
</a>
</td>
<td>
Option group suffix value
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_delete">
--delete
</a>
</td>
<td>
Empty the table before importing the text file
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_enable-cleartext-plugin">
--enable-cleartext-plugin
</a>
</td>
<td>
Enable cleartext authentication plugin
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_fields">
--fields-enclosed-by
</a>
</td>
<td>
This option has the same meaning as the corresponding clause for LOAD DATA
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_fields">
--fields-escaped-by
</a>
</td>
<td>
This option has the same meaning as the corresponding clause for LOAD DATA
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_fields">
--fields-optionally-enclosed-by
</a>
</td>
<td>
This option has the same meaning as the corresponding clause for LOAD DATA
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_fields">
--fields-terminated-by
</a>
</td>
<td>
This option has the same meaning as the corresponding clause for LOAD DATA
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_force">
--force
</a>
</td>
<td>
Continue even if an SQL error occurs
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_get-server-public-key">
--get-server-public-key
</a>
</td>
<td>
Request RSA public key from server
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_help">
--help
</a>
</td>
<td>
Display help message and exit
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_host">
--host
</a>
</td>
<td>
Host on which MySQL server is located
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ignore">
--ignore
</a>
</td>
<td>
See the description for the --replace option
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ignore-lines">
--ignore-lines
</a>
</td>
<td>
Ignore the first N lines of the data file
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_lines-terminated-by">
--lines-terminated-by
</a>
</td>
<td>
This option has the same meaning as the corresponding clause for LOAD DATA
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_local">
--local
</a>
</td>
<td>
Read input files locally from the client host
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_lock-tables">
--lock-tables
</a>
</td>
<td>
Lock all tables for writing before processing any text files
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_login-path">
--login-path
</a>
</td>
<td>
Read login path options from .mylogin.cnf
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_low-priority">
--low-priority
</a>
</td>
<td>
Use LOW_PRIORITY when loading the table
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_no-defaults">
--no-defaults
</a>
</td>
<td>
Read no option files
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_no-login-paths">
--no-login-paths
</a>
</td>
<td>
Do not read login paths from the login path file
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_password">
--password
</a>
</td>
<td>
Password to use when connecting to server
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_password1">
--password1
</a>
</td>
<td>
First multifactor authentication password to use when connecting to server
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_password2">
--password2
</a>
</td>
<td>
Second multifactor authentication password to use when connecting to server
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_password3">
--password3
</a>
</td>
<td>
Third multifactor authentication password to use when connecting to server
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_pipe">
--pipe
</a>
</td>
<td>
Connect to server using named pipe (Windows only)
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_plugin-dir">
--plugin-dir
</a>
</td>
<td>
Directory where plugins are installed
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_port">
--port
</a>
</td>
<td>
TCP/IP port number for connection
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_print-defaults">
--print-defaults
</a>
</td>
<td>
Print default options
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_protocol">
--protocol
</a>
</td>
<td>
Transport protocol to use
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_replace">
--replace
</a>
</td>
<td>
The --replace and --ignore options control handling of input rows that duplicate existing rows on unique key values
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_server-public-key-path">
--server-public-key-path
</a>
</td>
<td>
Path name to file containing RSA public key
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_shared-memory-base-name">
--shared-memory-base-name
</a>
</td>
<td>
Shared-memory name for shared-memory connections (Windows only)
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_silent">
--silent
</a>
</td>
<td>
Produce output only when errors occur
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_socket">
--socket
</a>
</td>
<td>
Unix socket file or Windows named pipe to use
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl">
--ssl-ca
</a>
</td>
<td>
File that contains list of trusted SSL Certificate Authorities
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl">
--ssl-capath
</a>
</td>
<td>
Directory that contains trusted SSL Certificate Authority certificate files
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl">
--ssl-cert
</a>
</td>
<td>
File that contains X.509 certificate
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl">
--ssl-cipher
</a>
</td>
<td>
Permissible ciphers for connection encryption
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl">
--ssl-crl
</a>
</td>
<td>
File that contains certificate revocation lists
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl">
--ssl-crlpath
</a>
</td>
<td>
Directory that contains certificate revocation-list files
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl-fips-mode">
--ssl-fips-mode
</a>
</td>
<td>
Whether to enable FIPS mode on client side
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl">
--ssl-key
</a>
</td>
<td>
File that contains X.509 key
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl">
--ssl-mode
</a>
</td>
<td>
Desired security state of connection to server
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl">
--ssl-session-data
</a>
</td>
<td>
File that contains SSL session data
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl">
--ssl-session-data-continue-on-failed-reuse
</a>
</td>
<td>
Whether to establish connections if session reuse fails
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_tls-ciphersuites">
--tls-ciphersuites
</a>
</td>
<td>
Permissible TLSv1.3 ciphersuites for encrypted connections
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_tls-sni-servername">
--tls-sni-servername
</a>
</td>
<td>
Server name supplied by the client
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_tls-version">
--tls-version
</a>
</td>
<td>
Permissible TLS protocols for encrypted connections
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_use-threads">
--use-threads
</a>
</td>
<td>
Number of threads for parallel file-loading
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_user">
--user
</a>
</td>
<td>
MySQL user name to use when connecting to server
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_verbose">
--verbose
</a>
</td>
<td>
Verbose mode
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_version">
--version
</a>
</td>
<td>
Display version information and exit
</td>
</tr>
<tr>
<td>
<a class="link" href="mysqlimport.html#option_mysqlimport_zstd-compression-level">
--zstd-compression-level
</a>
</td>
<td>
Compression level for connections to server that use zstd compression
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 739px;">
<thead>
<tr>
<th style="width: 260.906px;">
Option Name
</th>
<th style="width: 477.094px;">
Description
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="option_mysqlimport_help">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_help">
<code class="option">
--help
</code>
</a>
,
<code class="option">
-?
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for help">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--help
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311738096">
</a>
<a class="indexterm" name="idm46045311736608">
</a>
<p>
Display a help message and exit.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_bind-address">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_bind-address">
<code class="option">
--bind-address=
<em class="replaceable">
<code>
ip_address
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for bind-address">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--bind-address=ip_address
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311726640">
</a>
<a class="indexterm" name="idm46045311725152">
</a>
<p>
On a computer having multiple network interfaces, use this
option to select which interface to use for connecting to
the MySQL server.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_character-sets-dir">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_character-sets-dir">
<code class="option">
--character-sets-dir=
<em class="replaceable">
<code>
dir_name
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for character-sets-dir">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--character-sets-dir=path
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
[none]
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311710576">
</a>
<a class="indexterm" name="idm46045311709072">
</a>
<p>
The directory where character sets are installed. See
<a class="xref" href="charset-configuration.html" title="12.15 Character Set Configuration">
Section 12.15, “Character Set Configuration”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_columns">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_columns">
<code class="option">
--columns=
<em class="replaceable">
<code>
column_list
</code>
</em>
</code>
</a>
,
<code class="option">
-c
<em class="replaceable">
<code>
column_list
</code>
</em>
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for columns">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--columns=column_list
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311697680">
</a>
<a class="indexterm" name="idm46045311696192">
</a>
<p>
This option takes a list of comma-separated column names as
its value. The order of the column names indicates how to
match data file columns with table columns.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_compress">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_compress">
<code class="option">
--compress
</code>
</a>
,
<code class="option">
-C
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for compress">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--compress[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
Deprecated
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311679504">
</a>
<a class="indexterm" name="idm46045311678016">
</a>
<p>
Compress all information sent between the client and the
server if possible. See
<a class="xref" href="connection-compression-control.html" title="6.2.8 Connection Compression Control">
Section 6.2.8, “Connection Compression Control”
</a>
.
</p>
<p>
This option is deprecated. Expect it to be removed in a
future version of MySQL. See
<a class="xref" href="connection-compression-control.html#connection-compression-legacy-configuration" title="Configuring Legacy Connection Compression">
Configuring Legacy Connection Compression
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_compression-algorithms">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_compression-algorithms">
<code class="option">
--compression-algorithms=
<em class="replaceable">
<code>
value
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for compression-algorithms">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--compression-algorithms=value
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Set
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
uncompressed
</code>
</td>
</tr>
<tr>
<th>
Valid Values
</th>
<td>
<p class="valid-value">
<code class="literal">
zlib
</code>
</p>
<p class="valid-value">
<code class="literal">
zstd
</code>
</p>
<p class="valid-value">
<code class="literal">
uncompressed
</code>
</p>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311656704">
</a>
<a class="indexterm" name="idm46045311655200">
</a>
<p>
The permitted compression algorithms for connections to the
server. The available algorithms are the same as for the
<a class="link" href="server-system-variables.html#sysvar_protocol_compression_algorithms">
<code class="literal">
protocol_compression_algorithms
</code>
</a>
system variable. The default value is
<code class="literal">
uncompressed
</code>
.
</p>
<p>
For more information, see
<a class="xref" href="connection-compression-control.html" title="6.2.8 Connection Compression Control">
Section 6.2.8, “Connection Compression Control”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_debug">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_debug">
<code class="option">
--debug[=
<em class="replaceable">
<code>
debug_options
</code>
</em>
]
</code>
</a>
,
<code class="option">
-#
[
<em class="replaceable">
<code>
debug_options
</code>
</em>
]
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for debug">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--debug[=debug_options]
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
d:t:o
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311636480">
</a>
<a class="indexterm" name="idm46045311634992">
</a>
<p>
Write a debugging log. A typical
<em class="replaceable">
<code>
debug_options
</code>
</em>
string is
<code class="literal">
d:t:o,
<em class="replaceable">
<code>
file_name
</code>
</em>
</code>
.
The default is
<code class="literal">
d:t:o
</code>
.
</p>
<p>
This option is available only if MySQL was built using
<a class="link" href="source-configuration-options.html#option_cmake_with_debug">
<code class="option">
WITH_DEBUG
</code>
</a>
. MySQL release
binaries provided by Oracle are
<span class="emphasis">
<em>
not
</em>
</span>
built using this option.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_debug-check">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_debug-check">
<code class="option">
--debug-check
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for debug-check">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--debug-check
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
FALSE
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311616752">
</a>
<a class="indexterm" name="idm46045311615264">
</a>
<p>
Print some debugging information when the program exits.
</p>
<p>
This option is available only if MySQL was built using
<a class="link" href="source-configuration-options.html#option_cmake_with_debug">
<code class="option">
WITH_DEBUG
</code>
</a>
. MySQL release
binaries provided by Oracle are
<span class="emphasis">
<em>
not
</em>
</span>
built using this option.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_debug-info">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_debug-info">
<code class="option">
--debug-info
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for debug-info">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--debug-info
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
FALSE
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311599152">
</a>
<a class="indexterm" name="idm46045311597664">
</a>
<p>
Print debugging information and memory and CPU usage
statistics when the program exits.
</p>
<p>
This option is available only if MySQL was built using
<a class="link" href="source-configuration-options.html#option_cmake_with_debug">
<code class="option">
WITH_DEBUG
</code>
</a>
. MySQL release
binaries provided by Oracle are
<span class="emphasis">
<em>
not
</em>
</span>
built using this option.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_default-character-set">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_default-character-set">
<code class="option">
--default-character-set=
<em class="replaceable">
<code>
charset_name
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for default-character-set">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--default-character-set=charset_name
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311583504">
</a>
<a class="indexterm" name="idm46045311582000">
</a>
<p>
Use
<em class="replaceable">
<code>
charset_name
</code>
</em>
as the default
character set. See
<a class="xref" href="charset-configuration.html" title="12.15 Character Set Configuration">
Section 12.15, “Character Set Configuration”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_default-auth">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_default-auth">
<code class="option">
--default-auth=
<em class="replaceable">
<code>
plugin
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for default-auth">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--default-auth=plugin
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311568944">
</a>
<a class="indexterm" name="idm46045311567456">
</a>
<p>
A hint about which client-side authentication plugin to use.
See
<a class="xref" href="pluggable-authentication.html" title="8.2.17 Pluggable Authentication">
Section 8.2.17, “Pluggable Authentication”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_defaults-extra-file">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_defaults-extra-file">
<code class="option">
--defaults-extra-file=
<em class="replaceable">
<code>
file_name
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for defaults-extra-file">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--defaults-extra-file=file_name
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
File name
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311554704">
</a>
<a class="indexterm" name="idm46045311553200">
</a>
<p>
Read this option file after the global option file but (on
Unix) before the user option file. If the file does not
exist or is otherwise inaccessible, an error occurs. If
<em class="replaceable">
<code>
file_name
</code>
</em>
is not an absolute path
name, it is interpreted relative to the current directory.
</p>
<p>
For additional information about this and other option-file
options, see
<a class="xref" href="option-file-options.html" title="6.2.2.3 Command-Line Options that Affect Option-File Handling">
Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_defaults-file">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_defaults-file">
<code class="option">
--defaults-file=
<em class="replaceable">
<code>
file_name
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for defaults-file">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--defaults-file=file_name
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
File name
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311539296">
</a>
<a class="indexterm" name="idm46045311537808">
</a>
<p>
Use only the given option file. If the file does not exist
or is otherwise inaccessible, an error occurs. If
<em class="replaceable">
<code>
file_name
</code>
</em>
is not an absolute path
name, it is interpreted relative to the current directory.
</p>
<p>
Exception: Even with
<a class="link" href="option-file-options.html#option_general_defaults-file">
<code class="option">
--defaults-file
</code>
</a>
, client
programs read
<code class="filename">
.mylogin.cnf
</code>
.
</p>
<p>
For additional information about this and other option-file
options, see
<a class="xref" href="option-file-options.html" title="6.2.2.3 Command-Line Options that Affect Option-File Handling">
Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_defaults-group-suffix">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_defaults-group-suffix">
<code class="option">
--defaults-group-suffix=
<em class="replaceable">
<code>
str
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for defaults-group-suffix">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--defaults-group-suffix=str
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311521712">
</a>
<a class="indexterm" name="idm46045311520208">
</a>
<p>
Read not only the usual option groups, but also groups with
the usual names and a suffix of
<em class="replaceable">
<code>
str
</code>
</em>
. For example,
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
normally reads the
<code class="literal">
[client]
</code>
and
<code class="literal">
[mysqlimport]
</code>
groups. If this option is
given as
<a class="link" href="mysqlimport.html#option_mysqlimport_defaults-group-suffix">
<code class="option">
--defaults-group-suffix=_other
</code>
</a>
,
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
also reads the
<code class="literal">
[client_other]
</code>
and
<code class="literal">
[mysqlimport_other]
</code>
groups.
</p>
<p>
For additional information about this and other option-file
options, see
<a class="xref" href="option-file-options.html" title="6.2.2.3 Command-Line Options that Affect Option-File Handling">
Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_delete">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_delete">
<code class="option">
--delete
</code>
</a>
,
<code class="option">
-D
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for delete">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--delete
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311502016">
</a>
<a class="indexterm" name="idm46045311500528">
</a>
<p>
Empty the table before importing the text file.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_enable-cleartext-plugin">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_enable-cleartext-plugin">
<code class="option">
--enable-cleartext-plugin
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for enable-cleartext-plugin">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--enable-cleartext-plugin
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
FALSE
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311486208">
</a>
<a class="indexterm" name="idm46045311484704">
</a>
<p>
Enable the
<code class="literal">
mysql_clear_password
</code>
cleartext
authentication plugin. (See
<a class="xref" href="cleartext-pluggable-authentication.html" title="8.4.1.4 Client-Side Cleartext Pluggable Authentication">
Section 8.4.1.4, “Client-Side Cleartext Pluggable Authentication”
</a>
.)
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_fields">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_fields">
<code class="option">
--fields-terminated-by=...
</code>
</a>
,
<a class="link" href="mysqlimport.html#option_mysqlimport_fields">
<code class="option">
--fields-enclosed-by=...
</code>
</a>
,
<a class="link" href="mysqlimport.html#option_mysqlimport_fields">
<code class="option">
--fields-optionally-enclosed-by=...
</code>
</a>
,
<a class="link" href="mysqlimport.html#option_mysqlimport_fields">
<code class="option">
--fields-escaped-by=...
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for fields-terminated-by">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--fields-terminated-by=string
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311468560">
</a>
<a class="indexterm" name="idm46045311467056">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for fields-enclosed-by">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--fields-enclosed-by=string
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311457968">
</a>
<a class="indexterm" name="idm46045311456464">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for fields-optionally-enclosed-by">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--fields-optionally-enclosed-by=string
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311447360">
</a>
<a class="indexterm" name="idm46045311445856">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for fields-escaped-by">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--fields-escaped-by
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311436784">
</a>
<a class="indexterm" name="idm46045311435280">
</a>
<p>
These options have the same meaning as the corresponding
clauses for
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD DATA
</code>
</a>
. See
<a class="xref" href="load-data.html" title="15.2.9 LOAD DATA Statement">
Section 15.2.9, “LOAD DATA Statement”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_force">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_force">
<code class="option">
--force
</code>
</a>
,
<code class="option">
-f
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for force">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--force
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311423216">
</a>
<a class="indexterm" name="idm46045311421728">
</a>
<p>
Ignore errors. For example, if a table for a text file does
not exist, continue processing any remaining files. Without
<a class="link" href="mysqlimport.html#option_mysqlimport_force">
<code class="option">
--force
</code>
</a>
,
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
exits if a table does not
exist.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_get-server-public-key">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_get-server-public-key">
<code class="option">
--get-server-public-key
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for get-server-public-key">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--get-server-public-key
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311407568">
</a>
<a class="indexterm" name="idm46045311406064">
</a>
<p>
Request from the server the public key required for RSA key
pair-based password exchange. This option applies to clients
that authenticate with the
<code class="literal">
caching_sha2_password
</code>
authentication
plugin. For that plugin, the server does not send the public
key unless requested. This option is ignored for accounts
that do not authenticate with that plugin. It is also
ignored if RSA-based password exchange is not used, as is
the case when the client connects to the server using a
secure connection.
</p>
<p>
If
<a class="link" href="mysqlimport.html#option_mysqlimport_server-public-key-path">
<code class="option">
--server-public-key-path=
<em class="replaceable">
<code>
file_name
</code>
</em>
</code>
</a>
is given and specifies a valid public key file, it takes
precedence over
<a class="link" href="mysqlimport.html#option_mysqlimport_get-server-public-key">
<code class="option">
--get-server-public-key
</code>
</a>
.
</p>
<p>
For information about the
<code class="literal">
caching_sha2_password
</code>
plugin, see
<a class="xref" href="caching-sha2-pluggable-authentication.html" title="8.4.1.2 Caching SHA-2 Pluggable Authentication">
Section 8.4.1.2, “Caching SHA-2 Pluggable Authentication”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_host">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_host">
<code class="option">
--host=
<em class="replaceable">
<code>
host_name
</code>
</em>
</code>
</a>
,
<code class="option">
-h
<em class="replaceable">
<code>
host_name
</code>
</em>
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for host">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--host=host_name
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
localhost
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311385040">
</a>
<a class="indexterm" name="idm46045311383552">
</a>
<p>
Import data to the MySQL server on the given host. The
default host is
<code class="literal">
localhost
</code>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_ignore">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_ignore">
<code class="option">
--ignore
</code>
</a>
,
<code class="option">
-i
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for ignore">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--ignore
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311372688">
</a>
<a class="indexterm" name="idm46045311371200">
</a>
<p>
See the description for the
<a class="link" href="mysqlimport.html#option_mysqlimport_replace">
<code class="option">
--replace
</code>
</a>
option.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_ignore-lines">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_ignore-lines">
<code class="option">
--ignore-lines=
<em class="replaceable">
<code>
N
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for ignore-lines">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--ignore-lines=#
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Numeric
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311358304">
</a>
<a class="indexterm" name="idm46045311356816">
</a>
<p>
Ignore the first
<em class="replaceable">
<code>
N
</code>
</em>
lines of the
data file.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_lines-terminated-by">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_lines-terminated-by">
<code class="option">
--lines-terminated-by=...
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lines-terminated-by">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lines-terminated-by=string
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311344656">
</a>
<a class="indexterm" name="idm46045311343152">
</a>
<p>
This option has the same meaning as the corresponding clause
for
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD DATA
</code>
</a>
. For example,
to import Windows files that have lines terminated with
carriage return/linefeed pairs, use
<a class="link" href="mysqlimport.html#option_mysqlimport_lines-terminated-by">
<code class="option">
--lines-terminated-by="\r\n"
</code>
</a>
.
(You might have to double the backslashes, depending on the
escaping conventions of your command interpreter.) See
<a class="xref" href="load-data.html" title="15.2.9 LOAD DATA Statement">
Section 15.2.9, “LOAD DATA Statement”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_local">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_local">
<code class="option">
--local
</code>
</a>
,
<code class="option">
-L
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for local">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--local
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
FALSE
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311325312">
</a>
<a class="indexterm" name="idm46045311323824">
</a>
<p>
By default, files are read by the server on the server host.
With this option,
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
reads input
files locally on the client host.
</p>
<p>
Successful use of
<code class="literal">
LOCAL
</code>
load operations
within
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
also requires that the
server permits local loading; see
<a class="xref" href="load-data-local-security.html" title="8.1.6 Security Considerations for LOAD DATA LOCAL">
Section 8.1.6, “Security Considerations for LOAD DATA LOCAL”
</a>
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_lock-tables">
</a>
<a class="link" href="mysqldump.html#option_mysqldump_lock-tables">
<code class="option">
--lock-tables
</code>
</a>
,
<code class="option">
-l
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for lock-tables">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--lock-tables
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311309328">
</a>
<a class="indexterm" name="idm46045311307840">
</a>
<p>
Lock
<span class="emphasis">
<em>
all
</em>
</span>
tables for writing before
processing any text files. This ensures that all tables are
synchronized on the server.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_login-path">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_login-path">
<code class="option">
--login-path=
<em class="replaceable">
<code>
name
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for login-path">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--login-path=name
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311295344">
</a>
<a class="indexterm" name="idm46045311293856">
</a>
<p>
Read options from the named login path in the
<code class="filename">
.mylogin.cnf
</code>
login path file. A
<span class="quote">
“
<span class="quote">
login path
</span>
”
</span>
is an option group containing
options that specify which MySQL server to connect to and
which account to authenticate as. To create or modify a
login path file, use the
<a class="link" href="mysql-config-editor.html" title="6.6.7 mysql_config_editor — MySQL Configuration Utility">
<span class="command">
<strong>
mysql_config_editor
</strong>
</span>
</a>
utility. See
<a class="xref" href="mysql-config-editor.html" title="6.6.7 mysql_config_editor — MySQL Configuration Utility">
Section 6.6.7, “mysql_config_editor — MySQL Configuration Utility”
</a>
.
</p>
<p>
For additional information about this and other option-file
options, see
<a class="xref" href="option-file-options.html" title="6.2.2.3 Command-Line Options that Affect Option-File Handling">
Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_no-login-paths">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_no-login-paths">
<code class="option">
--no-login-paths
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for no-login-paths">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--no-login-paths
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311279712">
</a>
<a class="indexterm" name="idm46045311278224">
</a>
<p>
Skips reading options from the login path file.
</p>
<p>
See
<a class="link" href="mysqlimport.html#option_mysqlimport_login-path">
<code class="option">
--login-path
</code>
</a>
for
related information.
</p>
<p>
For additional information about this and other option-file
options, see
<a class="xref" href="option-file-options.html" title="6.2.2.3 Command-Line Options that Affect Option-File Handling">
Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_low-priority">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_low-priority">
<code class="option">
--low-priority
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for low-priority">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--low-priority
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311265952">
</a>
<a class="indexterm" name="idm46045311264464">
</a>
<p>
Use
<code class="literal">
LOW_PRIORITY
</code>
when loading the table.
This affects only storage engines that use only table-level
locking (such as
<code class="literal">
MyISAM
</code>
,
<code class="literal">
MEMORY
</code>
, and
<code class="literal">
MERGE
</code>
).
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_no-defaults">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_no-defaults">
<code class="option">
--no-defaults
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for no-defaults">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--no-defaults
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311251856">
</a>
<a class="indexterm" name="idm46045311250368">
</a>
<p>
Do not read any option files. If program startup fails due
to reading unknown options from an option file,
<a class="link" href="mysqlimport.html#option_mysqlimport_no-defaults">
<code class="option">
--no-defaults
</code>
</a>
can be
used to prevent them from being read.
</p>
<p>
The exception is that the
<code class="filename">
.mylogin.cnf
</code>
file is read in all cases, if it exists. This permits
passwords to be specified in a safer way than on the command
line even when
<a class="link" href="mysqlimport.html#option_mysqlimport_no-defaults">
<code class="option">
--no-defaults
</code>
</a>
is used.
To create
<code class="filename">
.mylogin.cnf
</code>
, use the
<a class="link" href="mysql-config-editor.html" title="6.6.7 mysql_config_editor — MySQL Configuration Utility">
<span class="command">
<strong>
mysql_config_editor
</strong>
</span>
</a>
utility. See
<a class="xref" href="mysql-config-editor.html" title="6.6.7 mysql_config_editor — MySQL Configuration Utility">
Section 6.6.7, “mysql_config_editor — MySQL Configuration Utility”
</a>
.
</p>
<p>
For additional information about this and other option-file
options, see
<a class="xref" href="option-file-options.html" title="6.2.2.3 Command-Line Options that Affect Option-File Handling">
Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_password">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_password">
<code class="option">
--password[=
<em class="replaceable">
<code>
password
</code>
</em>
]
</code>
</a>
,
<code class="option">
-p[
<em class="replaceable">
<code>
password
</code>
</em>
]
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for password">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--password[=password]
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311230128">
</a>
<a class="indexterm" name="idm46045311228640">
</a>
<p>
The password of the MySQL account used for connecting to the
server. The password value is optional. If not given,
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
prompts for one. If given,
there must be
<span class="emphasis">
<em>
no space
</em>
</span>
between
<a class="link" href="mysqlimport.html#option_mysqlimport_password">
<code class="option">
--password=
</code>
</a>
or
<code class="option">
-p
</code>
and the password following it. If no
password option is specified, the default is to send no
password.
</p>
<p>
Specifying a password on the command line should be
considered insecure. To avoid giving the password on the
command line, use an option file. See
<a class="xref" href="password-security-user.html" title="8.1.2.1 End-User Guidelines for Password Security">
Section 8.1.2.1, “End-User Guidelines for Password Security”
</a>
.
</p>
<p>
To explicitly specify that there is no password and that
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
should not prompt for one,
use the
<a class="link" href="mysqlimport.html#option_mysqlimport_password">
<code class="option">
--skip-password
</code>
</a>
option.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_password1">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_password1">
<code class="option">
--password1[=
<em class="replaceable">
<code>
pass_val
</code>
</em>
]
</code>
</a>
</p>
<a class="indexterm" name="idm46045311216704">
</a>
<p>
The password for multifactor authentication factor 1 of the
MySQL account used for connecting to the server. The
password value is optional. If not given,
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
prompts for one. If given,
there must be
<span class="emphasis">
<em>
no space
</em>
</span>
between
<a class="link" href="mysqlimport.html#option_mysqlimport_password1">
<code class="option">
--password1=
</code>
</a>
and the
password following it. If no password option is specified,
the default is to send no password.
</p>
<p>
Specifying a password on the command line should be
considered insecure. To avoid giving the password on the
command line, use an option file. See
<a class="xref" href="password-security-user.html" title="8.1.2.1 End-User Guidelines for Password Security">
Section 8.1.2.1, “End-User Guidelines for Password Security”
</a>
.
</p>
<p>
To explicitly specify that there is no password and that
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
should not prompt for one,
use the
<a class="link" href="mysqlimport.html#option_mysqlimport_password1">
<code class="option">
--skip-password1
</code>
</a>
option.
</p>
<p>
<a class="link" href="mysqlimport.html#option_mysqlimport_password1">
<code class="option">
--password1
</code>
</a>
and
<a class="link" href="mysqlimport.html#option_mysqlimport_password">
<code class="option">
--password
</code>
</a>
are
synonymous, as are
<a class="link" href="mysqlimport.html#option_mysqlimport_password1">
<code class="option">
--skip-password1
</code>
</a>
and
<a class="link" href="mysqlimport.html#option_mysqlimport_password">
<code class="option">
--skip-password
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_password2">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_password2">
<code class="option">
--password2[=
<em class="replaceable">
<code>
pass_val
</code>
</em>
]
</code>
</a>
</p>
<a class="indexterm" name="idm46045311201152">
</a>
<p>
The password for multifactor authentication factor 2 of the
MySQL account used for connecting to the server. The
semantics of this option are similar to the semantics for
<a class="link" href="mysqlimport.html#option_mysqlimport_password1">
<code class="option">
--password1
</code>
</a>
; see the
description of that option for details.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_password3">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_password3">
<code class="option">
--password3[=
<em class="replaceable">
<code>
pass_val
</code>
</em>
]
</code>
</a>
</p>
<a class="indexterm" name="idm46045311195792">
</a>
<p>
The password for multifactor authentication factor 3 of the
MySQL account used for connecting to the server. The
semantics of this option are similar to the semantics for
<a class="link" href="mysqlimport.html#option_mysqlimport_password1">
<code class="option">
--password1
</code>
</a>
; see the
description of that option for details.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_pipe">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_pipe">
<code class="option">
--pipe
</code>
</a>
,
<code class="option">
-W
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for pipe">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--pipe
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311182992">
</a>
<a class="indexterm" name="idm46045311181504">
</a>
<p>
On Windows, connect to the server using a named pipe. This
option applies only if the server was started with the
<a class="link" href="server-system-variables.html#sysvar_named_pipe">
<code class="literal">
named_pipe
</code>
</a>
system variable
enabled to support named-pipe connections. In addition, the
user making the connection must be a member of the Windows
group specified by the
<a class="link" href="server-system-variables.html#sysvar_named_pipe_full_access_group">
<code class="literal">
named_pipe_full_access_group
</code>
</a>
system variable.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_plugin-dir">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_plugin-dir">
<code class="option">
--plugin-dir=
<em class="replaceable">
<code>
dir_name
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for plugin-dir">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--plugin-dir=dir_name
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Directory name
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311166688">
</a>
<a class="indexterm" name="idm46045311165200">
</a>
<p>
The directory in which to look for plugins. Specify this
option if the
<a class="link" href="mysqlimport.html#option_mysqlimport_default-auth">
<code class="option">
--default-auth
</code>
</a>
option is
used to specify an authentication plugin but
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
does not find it. See
<a class="xref" href="pluggable-authentication.html" title="8.2.17 Pluggable Authentication">
Section 8.2.17, “Pluggable Authentication”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_port">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_port">
<code class="option">
--port=
<em class="replaceable">
<code>
port_num
</code>
</em>
</code>
</a>
,
<code class="option">
-P
<em class="replaceable">
<code>
port_num
</code>
</em>
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for port">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--port=port_num
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Numeric
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
3306
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311147072">
</a>
<a class="indexterm" name="idm46045311145584">
</a>
<p>
For TCP/IP connections, the port number to use.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_print-defaults">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_print-defaults">
<code class="option">
--print-defaults
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for print-defaults">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--print-defaults
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311135920">
</a>
<a class="indexterm" name="idm46045311134432">
</a>
<p>
Print the program name and all options that it gets from
option files.
</p>
<p>
For additional information about this and other option-file
options, see
<a class="xref" href="option-file-options.html" title="6.2.2.3 Command-Line Options that Affect Option-File Handling">
Section 6.2.2.3, “Command-Line Options that Affect Option-File Handling”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_protocol">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_protocol">
<code class="option">
--protocol={TCP|SOCKET|PIPE|MEMORY}
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for protocol">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--protocol=type
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
[see text]
</code>
</td>
</tr>
<tr>
<th>
Valid Values
</th>
<td>
<p class="valid-value">
<code class="literal">
TCP
</code>
</p>
<p class="valid-value">
<code class="literal">
SOCKET
</code>
</p>
<p class="valid-value">
<code class="literal">
PIPE
</code>
</p>
<p class="valid-value">
<code class="literal">
MEMORY
</code>
</p>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311113360">
</a>
<a class="indexterm" name="idm46045311111872">
</a>
<p>
The transport protocol to use for connecting to the server.
It is useful when the other connection parameters normally
result in use of a protocol other than the one you want. For
details on the permissible values, see
<a class="xref" href="transport-protocols.html" title="6.2.7 Connection Transport Protocols">
Section 6.2.7, “Connection Transport Protocols”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_replace">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_replace">
<code class="option">
--replace
</code>
</a>
,
<code class="option">
-r
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for replace">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--replace
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311100864">
</a>
<a class="indexterm" name="idm46045311099376">
</a>
<p>
The
<a class="link" href="mysqlimport.html#option_mysqlimport_replace">
<code class="option">
--replace
</code>
</a>
and
<a class="link" href="mysqlimport.html#option_mysqlimport_ignore">
<code class="option">
--ignore
</code>
</a>
options control
handling of input rows that duplicate existing rows on
unique key values. If you specify
<a class="link" href="mysqlimport.html#option_mysqlimport_replace">
<code class="option">
--replace
</code>
</a>
, new rows
replace existing rows that have the same unique key value.
If you specify
<a class="link" href="mysqlimport.html#option_mysqlimport_ignore">
<code class="option">
--ignore
</code>
</a>
,
input rows that duplicate an existing row on a unique key
value are skipped. If you do not specify either option, an
error occurs when a duplicate key value is found, and the
rest of the text file is ignored.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_server-public-key-path">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_server-public-key-path">
<code class="option">
--server-public-key-path=
<em class="replaceable">
<code>
file_name
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for server-public-key-path">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--server-public-key-path=file_name
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
File name
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311082864">
</a>
<a class="indexterm" name="idm46045311081360">
</a>
<p>
The path name to a file in PEM format containing a
client-side copy of the public key required by the server
for RSA key pair-based password exchange. This option
applies to clients that authenticate with the
<code class="literal">
sha256_password
</code>
(deprecated) or
<code class="literal">
caching_sha2_password
</code>
authentication
plugin. This option is ignored for accounts that do not
authenticate with one of those plugins. It is also ignored
if RSA-based password exchange is not used, as is the case
when the client connects to the server using a secure
connection.
</p>
<p>
If
<a class="link" href="mysqlimport.html#option_mysqlimport_server-public-key-path">
<code class="option">
--server-public-key-path=
<em class="replaceable">
<code>
file_name
</code>
</em>
</code>
</a>
is given and specifies a valid public key file, it takes
precedence over
<a class="link" href="mysqlimport.html#option_mysqlimport_get-server-public-key">
<code class="option">
--get-server-public-key
</code>
</a>
.
</p>
<p>
For
<code class="literal">
sha256_password
</code>
(deprecated), this
option applies only if MySQL was built using OpenSSL.
</p>
<p>
For information about the
<code class="literal">
sha256_password
</code>
and
<code class="literal">
caching_sha2_password
</code>
plugins, see
<a class="xref" href="sha256-pluggable-authentication.html" title="8.4.1.3 SHA-256 Pluggable Authentication">
Section 8.4.1.3, “SHA-256 Pluggable Authentication”
</a>
, and
<a class="xref" href="caching-sha2-pluggable-authentication.html" title="8.4.1.2 Caching SHA-2 Pluggable Authentication">
Section 8.4.1.2, “Caching SHA-2 Pluggable Authentication”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_shared-memory-base-name">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_shared-memory-base-name">
<code class="option">
--shared-memory-base-name=
<em class="replaceable">
<code>
name
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for shared-memory-base-name">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--shared-memory-base-name=name
</code>
</td>
</tr>
<tr>
<th>
Platform Specific
</th>
<td>
Windows
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311059888">
</a>
<a class="indexterm" name="idm46045311058384">
</a>
<p>
On Windows, the shared-memory name to use for connections
made using shared memory to a local server. The default
value is
<code class="literal">
MYSQL
</code>
. The shared-memory name is
case-sensitive.
</p>
<p>
This option applies only if the server was started with the
<a class="link" href="server-system-variables.html#sysvar_shared_memory">
<code class="literal">
shared_memory
</code>
</a>
system
variable enabled to support shared-memory connections.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_silent">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_silent">
<code class="option">
--silent
</code>
</a>
,
<code class="option">
-s
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for silent">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--silent
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311045680">
</a>
<a class="indexterm" name="idm46045311044192">
</a>
<p>
Silent mode. Produce output only when errors occur.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_socket">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_socket">
<code class="option">
--socket=
<em class="replaceable">
<code>
path
</code>
</em>
</code>
</a>
,
<code class="option">
-S
<em class="replaceable">
<code>
path
</code>
</em>
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for socket">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--socket={file_name|pipe_name}
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045311031520">
</a>
<a class="indexterm" name="idm46045311030032">
</a>
<p>
For connections to
<code class="literal">
localhost
</code>
, the Unix
socket file to use, or, on Windows, the name of the named
pipe to use.
</p>
<p>
On Windows, this option applies only if the server was
started with the
<a class="link" href="server-system-variables.html#sysvar_named_pipe">
<code class="literal">
named_pipe
</code>
</a>
system variable enabled to support named-pipe connections.
In addition, the user making the connection must be a member
of the Windows group specified by the
<a class="link" href="server-system-variables.html#sysvar_named_pipe_full_access_group">
<code class="literal">
named_pipe_full_access_group
</code>
</a>
system variable.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_ssl">
</a>
<code class="option">
--ssl*
</code>
</p>
<a class="indexterm" name="idm46045311022448">
</a>
<a class="indexterm" name="idm46045311020960">
</a>
<p>
Options that begin with
<code class="option">
--ssl
</code>
specify
whether to connect to the server using encryption and
indicate where to find SSL keys and certificates. See
<a class="xref" href="connection-options.html#encrypted-connection-options" title="Command Options for Encrypted Connections">
Command Options for Encrypted Connections
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_ssl-fips-mode">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl-fips-mode">
<code class="option">
--ssl-fips-mode={OFF|ON|STRICT}
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for ssl-fips-mode">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--ssl-fips-mode={OFF|ON|STRICT}
</code>
</td>
</tr>
<tr>
<th>
Deprecated
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Enumeration
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
<tr>
<th>
Valid Values
</th>
<td>
<p class="valid-value">
<code class="literal">
OFF
</code>
</p>
<p class="valid-value">
<code class="literal">
ON
</code>
</p>
<p class="valid-value">
<code class="literal">
STRICT
</code>
</p>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045310998816">
</a>
<a class="indexterm" name="idm46045310997328">
</a>
<p>
Controls whether to enable FIPS mode on the client side. The
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl-fips-mode">
<code class="option">
--ssl-fips-mode
</code>
</a>
option
differs from other
<code class="option">
--ssl-
<em class="replaceable">
<code>
xxx
</code>
</em>
</code>
options in that it is not used to establish encrypted
connections, but rather to affect which cryptographic
operations to permit. See
<a class="xref" href="fips-mode.html" title="8.8 FIPS Support">
Section 8.8, “FIPS Support”
</a>
.
</p>
<p>
These
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl-fips-mode">
<code class="option">
--ssl-fips-mode
</code>
</a>
values are permitted:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
OFF
</code>
: Disable FIPS mode.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ON
</code>
: Enable FIPS mode.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
STRICT
</code>
: Enable
<span class="quote">
“
<span class="quote">
strict
</span>
”
</span>
FIPS mode.
</p>
</li>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If the OpenSSL FIPS Object Module is not available, the
only permitted value for
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl-fips-mode">
<code class="option">
--ssl-fips-mode
</code>
</a>
is
<code class="literal">
OFF
</code>
. In this case, setting
<a class="link" href="mysqlimport.html#option_mysqlimport_ssl-fips-mode">
<code class="option">
--ssl-fips-mode
</code>
</a>
to
<code class="literal">
ON
</code>
or
<code class="literal">
STRICT
</code>
causes
the client to produce a warning at startup and to operate
in non-FIPS mode.
</p>
</div>
<p>
This option is deprecated. Expect it to be removed in a
future version of MySQL.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_tls-ciphersuites">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_tls-ciphersuites">
<code class="option">
--tls-ciphersuites=
<em class="replaceable">
<code>
ciphersuite_list
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for tls-ciphersuites">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--tls-ciphersuites=ciphersuite_list
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045310970368">
</a>
<a class="indexterm" name="idm46045310968880">
</a>
<p>
The permissible ciphersuites for encrypted connections that
use TLSv1.3. The value is a list of one or more
colon-separated ciphersuite names. The ciphersuites that can
be named for this option depend on the SSL library used to
compile MySQL. For details, see
<a class="xref" href="encrypted-connection-protocols-ciphers.html" title="8.3.2 Encrypted Connection TLS Protocols and Ciphers">
Section 8.3.2, “Encrypted Connection TLS Protocols and Ciphers”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_tls-sni-servername">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_tls-sni-servername">
<code class="option">
--tls-sni-servername=
<em class="replaceable">
<code>
server_name
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for tls-sni-servername">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--tls-sni-servername=server_name
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045310955888">
</a>
<a class="indexterm" name="idm46045310954384">
</a>
<p>
When specified, the name is passed to the
<code class="literal">
libmysqlclient
</code>
C API library using the
<code class="literal">
MYSQL_OPT_TLS_SNI_SERVERNAME
</code>
option of
<a class="ulink" href="/doc/c-api/8.4/en/mysql-options.html" target="_top">
<code class="literal">
mysql_options()
</code>
</a>
. The server
name is not case-sensitive. To show which server name the
client specified for the current session, if any, check the
<a class="link" href="server-status-variables.html#statvar_Tls_sni_server_name">
<code class="literal">
Tls_sni_server_name
</code>
</a>
status
variable.
</p>
<p>
Server Name Indication (SNI) is an extension to the TLS
protocol (OpenSSL must be compiled using TLS extensions for
this option to function). The MySQL implementation of SNI
represents the client-side only.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_tls-version">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_tls-version">
<code class="option">
--tls-version=
<em class="replaceable">
<code>
protocol_list
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for tls-version">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--tls-version=protocol_list
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<p class="valid-value">
<code class="literal">
TLSv1,TLSv1.1,TLSv1.2,TLSv1.3
</code>
(OpenSSL 1.1.1 or higher)
</p>
<p class="valid-value">
<code class="literal">
TLSv1,TLSv1.1,TLSv1.2
</code>
(otherwise)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045310933440">
</a>
<a class="indexterm" name="idm46045310931952">
</a>
<p>
The permissible TLS protocols for encrypted connections. The
value is a list of one or more comma-separated protocol
names. The protocols that can be named for this option
depend on the SSL library used to compile MySQL. For
details, see
<a class="xref" href="encrypted-connection-protocols-ciphers.html" title="8.3.2 Encrypted Connection TLS Protocols and Ciphers">
Section 8.3.2, “Encrypted Connection TLS Protocols and Ciphers”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_user">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_user">
<code class="option">
--user=
<em class="replaceable">
<code>
user_name
</code>
</em>
</code>
</a>
,
<code class="option">
-u
<em class="replaceable">
<code>
user_name
</code>
</em>
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for user">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--user=user_name,
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045310918384">
</a>
<a class="indexterm" name="idm46045310916896">
</a>
<p>
The user name of the MySQL account to use for connecting to
the server.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_use-threads">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_use-threads">
<code class="option">
--use-threads=
<em class="replaceable">
<code>
N
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for use-threads">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--use-threads=#
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Numeric
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045310904880">
</a>
<a class="indexterm" name="idm46045310903392">
</a>
<p>
Load files in parallel using
<em class="replaceable">
<code>
N
</code>
</em>
threads.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_verbose">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_verbose">
<code class="option">
--verbose
</code>
</a>
,
<code class="option">
-v
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for verbose">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--verbose
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045310892864">
</a>
<a class="indexterm" name="idm46045310891376">
</a>
<p>
Verbose mode. Print more information about what the program
does.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_version">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_version">
<code class="option">
--version
</code>
</a>
,
<code class="option">
-V
</code>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for version">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--version
</code>
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045310881280">
</a>
<a class="indexterm" name="idm46045310879792">
</a>
<p>
Display version information and exit.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqlimport_zstd-compression-level">
</a>
<a class="link" href="mysqlimport.html#option_mysqlimport_zstd-compression-level">
<code class="option">
--zstd-compression-level=
<em class="replaceable">
<code>
level
</code>
</em>
</code>
</a>
</p>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for zstd-compression-level">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--zstd-compression-level=#
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
</tbody>
</table>
</div>
<a class="indexterm" name="idm46045310867680">
</a>
<a class="indexterm" name="idm46045310866176">
</a>
<p>
The compression level to use for connections to the server
that use the
<code class="literal">
zstd
</code>
compression algorithm.
The permitted levels are from 1 to 22, with larger values
indicating increasing levels of compression. The default
<code class="literal">
zstd
</code>
compression level is 3. The
compression level setting has no effect on connections that
do not use
<code class="literal">
zstd
</code>
compression.
</p>
<p>
For more information, see
<a class="xref" href="connection-compression-control.html" title="6.2.8 Connection Compression Control">
Section 6.2.8, “Connection Compression Control”
</a>
.
</p>
</li>
</ul>
</div>
<p>
Here is a sample session that demonstrates use of
<a class="link" href="mysqlimport.html" title="6.5.5 mysqlimport — A Data Import Program">
<span class="command">
<strong>
mysqlimport
</strong>
</span>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa63524895"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysql</span> <span class="token property">-e</span> <span class="token atrule">'CREATE TABLE imptest(id INT, n VARCHAR(30))'</span> test
<span class="token prompt">$> </span><span class="token command">ed</span>
a
100 Max Sydow
101 Count Dracula
<span class="token punctuation">.</span>
w imptest<span class="token punctuation">.</span>txt
32
q
<span class="token prompt">$> </span><span class="token command">od</span> <span class="token property">-c</span> imptest<span class="token punctuation">.</span>txt
0000000 1 0 0 \t M a x S y d o w \n 1 0
0000020 1 \t C o u n t D r a c u l a \n
0000040
<span class="token prompt">$> </span><span class="token command">mysqlimport</span> <span class="token property">--local</span> test imptest<span class="token punctuation">.</span>txt
test<span class="token punctuation">.</span>imptest<span class="token punctuation">:</span> Records<span class="token punctuation">:</span> 2 Deleted<span class="token punctuation">:</span> 0 Skipped<span class="token punctuation">:</span> 0 Warnings<span class="token punctuation">:</span> 0
<span class="token prompt">$> </span><span class="token command">mysql</span> <span class="token property">-e</span> <span class="token atrule">'SELECT * FROM imptest'</span> test
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> id <span class="token punctuation">|</span> n <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 100 <span class="token punctuation">|</span> Max Sydow <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 101 <span class="token punctuation">|</span> Count Dracula <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-statements-group.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="replication-statements-group">
</a>
15.4.3 SQL Statements for Controlling Group Replication
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="start-group-replication.html">
15.4.3.1 START GROUP_REPLICATION Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="stop-group-replication.html">
15.4.3.2 STOP GROUP_REPLICATION Statement
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045176859040">
</a>
<a class="indexterm" name="idm46045176857552">
</a>
<a class="indexterm" name="idm46045176856064">
</a>
<p>
This section provides information about the statements used for
controlling group replication.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-and-plugins.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="performance-schema-and-plugins">
</a>
29.18 Performance Schema and Plugins
</h2>
</div>
</div>
</div>
<p>
Removing a plugin with
<a class="link" href="uninstall-plugin.html" title="15.7.4.6 UNINSTALL PLUGIN Statement">
<code class="literal">
UNINSTALL
PLUGIN
</code>
</a>
does not affect information already collected for
code in that plugin. Time spent executing the code while the
plugin was loaded was still spent even if the plugin is unloaded
later. The associated event information, including aggregate
information, remains readable in
<code class="literal">
performance_schema
</code>
database tables. For
additional information about the effect of plugin installation and
removal, see
<a class="xref" href="performance-schema-status-monitoring.html" title="29.7 Performance Schema Status Monitoring">
Section 29.7, “Performance Schema Status Monitoring”
</a>
.
</p>
<p>
A plugin implementor who instruments plugin code should document
its instrumentation characteristics to enable those who load the
plugin to account for its requirements. For example, a third-party
storage engine should include in its documentation how much memory
the engine needs for mutex and other instruments.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/event-scheduler.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="event-scheduler">
</a>
27.4 Using the Event Scheduler
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="events-overview.html">
27.4.1 Event Scheduler Overview
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="events-configuration.html">
27.4.2 Event Scheduler Configuration
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="events-syntax.html">
27.4.3 Event Syntax
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="events-metadata.html">
27.4.4 Event Metadata
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="events-status-info.html">
27.4.5 Event Scheduler Status
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="events-privileges.html">
27.4.6 The Event Scheduler and MySQL Privileges
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045082265648">
</a>
<a class="indexterm" name="idm46045082264608">
</a>
<p>
The
<span class="firstterm">
MySQL Event Scheduler
</span>
manages the scheduling and execution of events, that is, tasks that
run according to a schedule. The following discussion covers the
Event Scheduler and is divided into the following sections:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="events-overview.html" title="27.4.1 Event Scheduler Overview">
Section 27.4.1, “Event Scheduler Overview”
</a>
, provides an introduction to
and conceptual overview of MySQL Events.
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="events-syntax.html" title="27.4.3 Event Syntax">
Section 27.4.3, “Event Syntax”
</a>
, discusses the SQL statements
for creating, altering, and dropping MySQL Events.
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="events-metadata.html" title="27.4.4 Event Metadata">
Section 27.4.4, “Event Metadata”
</a>
, shows how to obtain
information about events and how this information is stored by
the MySQL Server.
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="events-privileges.html" title="27.4.6 The Event Scheduler and MySQL Privileges">
Section 27.4.6, “The Event Scheduler and MySQL Privileges”
</a>
, discusses the privileges
required to work with events and the ramifications that events
have with regard to privileges when executing.
</p>
</li>
</ul>
</div>
<p>
Stored routines require the
<code class="literal">
events
</code>
data
dictionary table in the
<code class="literal">
mysql
</code>
system database.
This table is created during the MySQL 8.4 installation
procedure. If you are upgrading to MySQL 8.4 from an
earlier version, be sure to perform the upgrade procedure to make
sure that your system database is up to date. See
<a class="xref" href="upgrading.html" title="Chapter 3 Upgrading MySQL">
Chapter 3,
<i>
Upgrading MySQL
</i>
</a>
.
</p>
<h3>
<a name="idm46045082251744">
</a>
Additional Resources
</h3>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
There are some restrictions on the use of events; see
<a class="xref" href="stored-program-restrictions.html" title="27.8 Restrictions on Stored Programs">
Section 27.8, “Restrictions on Stored Programs”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Binary logging for events takes place as described in
<a class="xref" href="stored-programs-logging.html" title="27.7 Stored Program Binary Logging">
Section 27.7, “Stored Program Binary Logging”
</a>
.
</p>
</li>
<li class="listitem">
<p>
You may also find the
<a class="ulink" href="https://forums.mysql.com/list.php?20" target="_blank">
MySQL User Forums
</a>
to be helpful.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/information-schema-tp-thread-group-state-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="information-schema-tp-thread-group-state-table">
</a>
28.5.2 The INFORMATION_SCHEMA TP_THREAD_GROUP_STATE Table
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045076060800">
</a>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The
<code class="literal">
INFORMATION_SCHEMA
</code>
thread pool tables are
deprecated, and subject to removal in a future version of MySQL.
You should use the versions available as Performance Schema
tables insted. See
<a class="xref" href="performance-schema-thread-pool-tables.html" title="29.12.16 Performance Schema Thread Pool Tables">
Section 29.12.16, “Performance Schema Thread Pool Tables”
</a>
.
Applications should transition away from the old tables to the
new tables. For example, if an application uses this query:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa16908103"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>TP_THREAD_GROUP_STATE<span class="token punctuation">;</span></code></pre>
</div>
<p>
The application should use this query instead:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa3420930"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>tp_thread_group_state<span class="token punctuation">;</span></code></pre>
</div>
</div>
<p>
The
<code class="literal">
TP_THREAD_GROUP_STATE
</code>
table has one row per
thread group in the thread pool. Each row provides information
about the current state of a group.
</p>
<p>
For descriptions of the columns in the
<code class="literal">
INFORMATION_SCHEMA
</code>
<code class="literal">
TP_THREAD_GROUP_STATE
</code>
table, see
<a class="xref" href="performance-schema-tp-thread-group-state-table.html" title="29.12.16.2 The tp_thread_group_state Table">
Section 29.12.16.2, “The tp_thread_group_state Table”
</a>
.
The Performance Schema
<a class="link" href="performance-schema-tp-thread-group-state-table.html" title="29.12.16.2 The tp_thread_group_state Table">
<code class="literal">
tp_thread_group_state
</code>
</a>
table has
equivalent columns.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-by-modifiers.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="group-by-modifiers">
</a>
14.19.2 GROUP BY Modifiers
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045192776816">
</a>
<a class="indexterm" name="idm46045192775744">
</a>
<a class="indexterm" name="idm46045192774672">
</a>
<a class="indexterm" name="idm46045192773600">
</a>
<a class="indexterm" name="idm46045192772112">
</a>
<p>
The
<code class="literal">
GROUP BY
</code>
clause permits a
<code class="literal">
WITH
ROLLUP
</code>
modifier that causes summary output to include
extra rows that represent higher-level (that is,
super-aggregate) summary operations.
<code class="literal">
ROLLUP
</code>
thus enables you to answer questions at multiple levels of
analysis with a single query. For example,
<code class="literal">
ROLLUP
</code>
can be used to provide support for
OLAP (Online Analytical Processing) operations.
</p>
<p>
Suppose that a
<code class="literal">
sales
</code>
table has
<code class="literal">
year
</code>
,
<code class="literal">
country
</code>
,
<code class="literal">
product
</code>
, and
<code class="literal">
profit
</code>
columns for recording sales profitability:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa43138516"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> sales
<span class="token punctuation">(</span>
<span class="token datatype">year</span> <span class="token datatype">INT</span><span class="token punctuation">,</span>
country <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
product <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">32</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
profit <span class="token datatype">INT</span>
<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To summarize table contents per year, use a simple
<code class="literal">
GROUP BY
</code>
like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa86382169"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token datatype">year</span><span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>profit<span class="token punctuation">)</span> <span class="token keyword">AS</span> profit
<span class="token keyword">FROM</span> sales
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token datatype">year</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> year <span class="token punctuation">|</span> profit <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> 4525 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> 3010 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
The output shows the total (aggregate) profit for each year. To
also determine the total profit summed over all years, you must
add up the individual values yourself or run an additional
query. Or you can use
<code class="literal">
ROLLUP
</code>
, which provides
both levels of analysis with a single query. Adding a
<code class="literal">
WITH ROLLUP
</code>
modifier to the
<code class="literal">
GROUP
BY
</code>
clause causes the query to produce another
(super-aggregate) row that shows the grand total over all year
values:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa15470369"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token datatype">year</span><span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>profit<span class="token punctuation">)</span> <span class="token keyword">AS</span> profit
<span class="token keyword">FROM</span> sales
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token datatype">year</span> <span class="token keyword">WITH</span> <span class="token keyword">ROLLUP</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> year <span class="token punctuation">|</span> profit <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> 4525 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> 3010 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 7535 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
The
<code class="literal">
NULL
</code>
value in the
<code class="literal">
year
</code>
column identifies the grand total super-aggregate line.
</p>
<p>
<code class="literal">
ROLLUP
</code>
has a more complex effect when there
are multiple
<code class="literal">
GROUP BY
</code>
columns. In this case,
each time there is a change in value in any but the last
grouping column, the query produces an extra super-aggregate
summary row.
</p>
<p>
For example, without
<code class="literal">
ROLLUP
</code>
, a summary of the
<code class="literal">
sales
</code>
table based on
<code class="literal">
year
</code>
,
<code class="literal">
country
</code>
, and
<code class="literal">
product
</code>
might
look like this, where the output indicates summary values only
at the year/country/product level of analysis:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa20019911"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product<span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>profit<span class="token punctuation">)</span> <span class="token keyword">AS</span> profit
<span class="token keyword">FROM</span> sales
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> year <span class="token punctuation">|</span> country <span class="token punctuation">|</span> product <span class="token punctuation">|</span> profit <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1500 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Phone <span class="token punctuation">|</span> 100 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 150 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1200 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 75 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1500 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Phone <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 50 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 2700 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> TV <span class="token punctuation">|</span> 250 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
With
<code class="literal">
ROLLUP
</code>
added, the query produces several
extra rows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa67001293"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product<span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>profit<span class="token punctuation">)</span> <span class="token keyword">AS</span> profit
<span class="token keyword">FROM</span> sales
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product <span class="token keyword">WITH</span> <span class="token keyword">ROLLUP</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> year <span class="token punctuation">|</span> country <span class="token punctuation">|</span> product <span class="token punctuation">|</span> profit <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1500 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Phone <span class="token punctuation">|</span> 100 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 1600 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 150 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1200 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 1350 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 75 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1500 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 1575 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 4525 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Phone <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 50 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 2700 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> TV <span class="token punctuation">|</span> 250 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 3000 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 3010 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 7535 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Now the output includes summary information at four levels of
analysis, not just one:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Following each set of product rows for a given year and
country, an extra super-aggregate summary row appears
showing the total for all products. These rows have the
<code class="literal">
product
</code>
column set to
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
Following each set of rows for a given year, an extra
super-aggregate summary row appears showing the total for
all countries and products. These rows have the
<code class="literal">
country
</code>
and
<code class="literal">
products
</code>
columns set to
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
Finally, following all other rows, an extra super-aggregate
summary row appears showing the grand total for all years,
countries, and products. This row has the
<code class="literal">
year
</code>
,
<code class="literal">
country
</code>
, and
<code class="literal">
products
</code>
columns set to
<code class="literal">
NULL
</code>
.
</p>
</li>
</ul>
</div>
<p>
The
<code class="literal">
NULL
</code>
indicators in each super-aggregate
row are produced when the row is sent to the client. The server
looks at the columns named in the
<code class="literal">
GROUP BY
</code>
clause following the leftmost one that has changed value. For
any column in the result set with a name that matches any of
those names, its value is set to
<code class="literal">
NULL
</code>
. (If
you specify grouping columns by column position, the server
identifies which columns to set to
<code class="literal">
NULL
</code>
by
position.)
</p>
<p>
Because the
<code class="literal">
NULL
</code>
values in the
super-aggregate rows are placed into the result set at such a
late stage in query processing, you can test them as
<code class="literal">
NULL
</code>
values only in the select list or
<code class="literal">
HAVING
</code>
clause. You cannot test them as
<code class="literal">
NULL
</code>
values in join conditions or the
<code class="literal">
WHERE
</code>
clause to determine which rows to
select. For example, you cannot add
<code class="literal">
WHERE product IS
NULL
</code>
to the query to eliminate from the output all but
the super-aggregate rows.
</p>
<p>
The
<code class="literal">
NULL
</code>
values do appear as
<code class="literal">
NULL
</code>
on the client side and can be tested as
such using any MySQL client programming interface. However, at
this point, you cannot distinguish whether a
<code class="literal">
NULL
</code>
represents a regular grouped value or a
super-aggregate value. To test the distinction, use the
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING()
</code>
</a>
function, described
later.
</p>
<p>
For
<code class="literal">
GROUP BY ... WITH ROLLUP
</code>
queries, to test
whether
<code class="literal">
NULL
</code>
values in the result represent
super-aggregate values, the
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING()
</code>
</a>
function is available
for use in the select list,
<code class="literal">
HAVING
</code>
clause,
and
<code class="literal">
ORDER BY
</code>
clause. For example,
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING(year)
</code>
</a>
returns 1 when
<code class="literal">
NULL
</code>
in the
<code class="literal">
year
</code>
column
occurs in a super-aggregate row, and 0 otherwise. Similarly,
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING(country)
</code>
</a>
and
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING(product)
</code>
</a>
return 1 for
super-aggregate
<code class="literal">
NULL
</code>
values in the
<code class="literal">
country
</code>
and
<code class="literal">
product
</code>
columns, respectively:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa73998215"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span>
<span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product<span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>profit<span class="token punctuation">)</span> <span class="token keyword">AS</span> profit<span class="token punctuation">,</span>
<span class="token function">GROUPING</span><span class="token punctuation">(</span><span class="token datatype">year</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> grp_year<span class="token punctuation">,</span>
<span class="token function">GROUPING</span><span class="token punctuation">(</span>country<span class="token punctuation">)</span> <span class="token keyword">AS</span> grp_country<span class="token punctuation">,</span>
<span class="token function">GROUPING</span><span class="token punctuation">(</span>product<span class="token punctuation">)</span> <span class="token keyword">AS</span> grp_product
<span class="token keyword">FROM</span> sales
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product <span class="token keyword">WITH</span> <span class="token keyword">ROLLUP</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> year <span class="token punctuation">|</span> country <span class="token punctuation">|</span> product <span class="token punctuation">|</span> profit <span class="token punctuation">|</span> grp_year <span class="token punctuation">|</span> grp_country <span class="token punctuation">|</span> grp_product <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1500 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Phone <span class="token punctuation">|</span> 100 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 1600 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 150 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1200 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 1350 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 75 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1500 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 1575 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 4525 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Phone <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 50 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 2700 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> TV <span class="token punctuation">|</span> 250 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 3000 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 3010 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 7535 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Instead of displaying the
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING()
</code>
</a>
results directly, you
can use
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING()
</code>
</a>
to substitute
labels for super-aggregate
<code class="literal">
NULL
</code>
values:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99360513"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span>
<span class="token function">IF</span><span class="token punctuation">(</span><span class="token function">GROUPING</span><span class="token punctuation">(</span><span class="token datatype">year</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token string">'All years'</span><span class="token punctuation">,</span> <span class="token datatype">year</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> <span class="token datatype">year</span><span class="token punctuation">,</span>
<span class="token function">IF</span><span class="token punctuation">(</span><span class="token function">GROUPING</span><span class="token punctuation">(</span>country<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token string">'All countries'</span><span class="token punctuation">,</span> country<span class="token punctuation">)</span> <span class="token keyword">AS</span> country<span class="token punctuation">,</span>
<span class="token function">IF</span><span class="token punctuation">(</span><span class="token function">GROUPING</span><span class="token punctuation">(</span>product<span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token string">'All products'</span><span class="token punctuation">,</span> product<span class="token punctuation">)</span> <span class="token keyword">AS</span> product<span class="token punctuation">,</span>
<span class="token function">SUM</span><span class="token punctuation">(</span>profit<span class="token punctuation">)</span> <span class="token keyword">AS</span> profit
<span class="token keyword">FROM</span> sales
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product <span class="token keyword">WITH</span> <span class="token keyword">ROLLUP</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> year <span class="token punctuation">|</span> country <span class="token punctuation">|</span> product <span class="token punctuation">|</span> profit <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1500 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Phone <span class="token punctuation">|</span> 100 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> All products <span class="token punctuation">|</span> 1600 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 150 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1200 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> All products <span class="token punctuation">|</span> 1350 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 75 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1500 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> All products <span class="token punctuation">|</span> 1575 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> All countries <span class="token punctuation">|</span> All products <span class="token punctuation">|</span> 4525 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Phone <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> All products <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 50 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 2700 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> TV <span class="token punctuation">|</span> 250 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> All products <span class="token punctuation">|</span> 3000 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> All countries <span class="token punctuation">|</span> All products <span class="token punctuation">|</span> 3010 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> All years <span class="token punctuation">|</span> All countries <span class="token punctuation">|</span> All products <span class="token punctuation">|</span> 7535 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
With multiple expression arguments,
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING()
</code>
</a>
returns a result
representing a bitmask that combines the results for each
expression, with the lowest-order bit corresponding to the
result for the rightmost expression. For example,
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING(year, country, product)
</code>
</a>
is evaluated like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa2509228"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"> result <span class="token keyword">for</span> <span class="token function">GROUPING</span><span class="token punctuation">(</span><em class="replaceable">product</em><span class="token punctuation">)</span>
<span class="token operator">+</span> result <span class="token keyword">for</span> <span class="token function">GROUPING</span><span class="token punctuation">(</span><em class="replaceable">country</em><span class="token punctuation">)</span> <span class="token operator"><</span><span class="token operator"><</span> <span class="token number">1</span>
<span class="token operator">+</span> result <span class="token keyword">for</span> <span class="token function">GROUPING</span><span class="token punctuation">(</span><em class="replaceable">year</em><span class="token punctuation">)</span> <span class="token operator"><</span><span class="token operator"><</span> <span class="token number">2</span></code></pre>
</div>
<p>
The result of such a
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING()
</code>
</a>
is nonzero if any of the expressions represents a
super-aggregate
<code class="literal">
NULL
</code>
, so you can return only
the super-aggregate rows and filter out the regular grouped rows
like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa69606547"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product<span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>profit<span class="token punctuation">)</span> <span class="token keyword">AS</span> profit
<span class="token keyword">FROM</span> sales
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product <span class="token keyword">WITH</span> <span class="token keyword">ROLLUP</span>
<span class="token keyword">HAVING</span> <span class="token function">GROUPING</span><span class="token punctuation">(</span><span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product<span class="token punctuation">)</span> <span class="token operator"><></span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> year <span class="token punctuation">|</span> country <span class="token punctuation">|</span> product <span class="token punctuation">|</span> profit <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 1600 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 1350 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 1575 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 4525 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 3000 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 3010 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 7535 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
The
<code class="literal">
sales
</code>
table contains no
<code class="literal">
NULL
</code>
values, so all
<code class="literal">
NULL
</code>
values in a
<code class="literal">
ROLLUP
</code>
result represent
super-aggregate values. When the data set contains
<code class="literal">
NULL
</code>
values,
<code class="literal">
ROLLUP
</code>
summaries may contain
<code class="literal">
NULL
</code>
values not only in
super-aggregate rows, but also in regular grouped rows.
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING()
</code>
</a>
enables these to be
distinguished. Suppose that table
<code class="literal">
t1
</code>
contains
a simple data set with two grouping factors for a set of
quantity values, where
<code class="literal">
NULL
</code>
indicates
something like
<span class="quote">
“
<span class="quote">
other
</span>
”
</span>
or
<span class="quote">
“
<span class="quote">
unknown
</span>
”
</span>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa7113465"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t1<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> name <span class="token punctuation">|</span> size <span class="token punctuation">|</span> quantity <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ball <span class="token punctuation">|</span> small <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ball <span class="token punctuation">|</span> large <span class="token punctuation">|</span> 20 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ball <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hoop <span class="token punctuation">|</span> small <span class="token punctuation">|</span> 15 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hoop <span class="token punctuation">|</span> large <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hoop <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
A simple
<code class="literal">
ROLLUP
</code>
operation produces these
results, in which it is not so easy to distinguish
<code class="literal">
NULL
</code>
values in super-aggregate rows from
<code class="literal">
NULL
</code>
values in regular grouped rows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa86556644"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token keyword">name</span><span class="token punctuation">,</span> size<span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>quantity<span class="token punctuation">)</span> <span class="token keyword">AS</span> quantity
<span class="token keyword">FROM</span> t1
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token keyword">name</span><span class="token punctuation">,</span> size <span class="token keyword">WITH</span> <span class="token keyword">ROLLUP</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> name <span class="token punctuation">|</span> size <span class="token punctuation">|</span> quantity <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ball <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ball <span class="token punctuation">|</span> large <span class="token punctuation">|</span> 20 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ball <span class="token punctuation">|</span> small <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ball <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 35 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hoop <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hoop <span class="token punctuation">|</span> large <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hoop <span class="token punctuation">|</span> small <span class="token punctuation">|</span> 15 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hoop <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 23 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 58 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Using
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING()
</code>
</a>
to substitute
labels for the super-aggregate
<code class="literal">
NULL
</code>
values
makes the result easier to interpret:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa89217868"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span>
<span class="token function">IF</span><span class="token punctuation">(</span><span class="token function">GROUPING</span><span class="token punctuation">(</span><span class="token keyword">name</span><span class="token punctuation">)</span> <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">'All items'</span><span class="token punctuation">,</span> <span class="token keyword">name</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> <span class="token keyword">name</span><span class="token punctuation">,</span>
<span class="token function">IF</span><span class="token punctuation">(</span><span class="token function">GROUPING</span><span class="token punctuation">(</span>size<span class="token punctuation">)</span> <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">'All sizes'</span><span class="token punctuation">,</span> size<span class="token punctuation">)</span> <span class="token keyword">AS</span> size<span class="token punctuation">,</span>
<span class="token function">SUM</span><span class="token punctuation">(</span>quantity<span class="token punctuation">)</span> <span class="token keyword">AS</span> quantity
<span class="token keyword">FROM</span> t1
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token keyword">name</span><span class="token punctuation">,</span> size <span class="token keyword">WITH</span> <span class="token keyword">ROLLUP</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> name <span class="token punctuation">|</span> size <span class="token punctuation">|</span> quantity <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ball <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ball <span class="token punctuation">|</span> large <span class="token punctuation">|</span> 20 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ball <span class="token punctuation">|</span> small <span class="token punctuation">|</span> 10 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> ball <span class="token punctuation">|</span> All sizes <span class="token punctuation">|</span> 35 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hoop <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hoop <span class="token punctuation">|</span> large <span class="token punctuation">|</span> 5 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hoop <span class="token punctuation">|</span> small <span class="token punctuation">|</span> 15 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> hoop <span class="token punctuation">|</span> All sizes <span class="token punctuation">|</span> 23 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> All items <span class="token punctuation">|</span> All sizes <span class="token punctuation">|</span> 58 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="group-by-modifiers-other-considerations-when-using-rollup">
</a>
Other Considerations When using ROLLUP
</h4>
</div>
</div>
</div>
<p>
The following discussion lists some behaviors specific to the
MySQL implementation of
<code class="literal">
ROLLUP
</code>
.
</p>
<p>
<code class="literal">
ORDER BY
</code>
and
<code class="literal">
ROLLUP
</code>
can
be used together, which enables the use of
<code class="literal">
ORDER
BY
</code>
and
<a class="link" href="miscellaneous-functions.html#function_grouping">
<code class="literal">
GROUPING()
</code>
</a>
to
achieve a specific sort order of grouped results. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa5297568"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token datatype">year</span><span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>profit<span class="token punctuation">)</span> <span class="token keyword">AS</span> profit
<span class="token keyword">FROM</span> sales
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token datatype">year</span> <span class="token keyword">WITH</span> <span class="token keyword">ROLLUP</span>
<span class="token keyword">ORDER</span> <span class="token keyword">BY</span> <span class="token function">GROUPING</span><span class="token punctuation">(</span><span class="token datatype">year</span><span class="token punctuation">)</span> <span class="token keyword">DESC</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> year <span class="token punctuation">|</span> profit <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 7535 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> 4525 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> 3010 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
In both cases, the super-aggregate summary rows sort with the
rows from which they are calculated, and their placement
depends on sort order (at the end for ascending sort, at the
beginning for descending sort).
</p>
<p>
<code class="literal">
LIMIT
</code>
can be used to restrict the number of
rows returned to the client.
<code class="literal">
LIMIT
</code>
is
applied after
<code class="literal">
ROLLUP
</code>
, so the limit applies
against the extra rows added by
<code class="literal">
ROLLUP
</code>
. For
example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa68469933"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product<span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>profit<span class="token punctuation">)</span> <span class="token keyword">AS</span> profit
<span class="token keyword">FROM</span> sales
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> product <span class="token keyword">WITH</span> <span class="token keyword">ROLLUP</span>
<span class="token keyword">LIMIT</span> <span class="token number">5</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> year <span class="token punctuation">|</span> country <span class="token punctuation">|</span> product <span class="token punctuation">|</span> profit <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1500 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> Phone <span class="token punctuation">|</span> 100 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> Finland <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 1600 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> Calculator <span class="token punctuation">|</span> 150 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> Computer <span class="token punctuation">|</span> 1200 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Using
<code class="literal">
LIMIT
</code>
with
<code class="literal">
ROLLUP
</code>
may produce results that are more difficult to interpret,
because there is less context for understanding the
super-aggregate rows.
</p>
<p>
A MySQL extension permits a column that does not appear in the
<code class="literal">
GROUP BY
</code>
list to be named in the select
list. (For information about nonaggregated columns and
<code class="literal">
GROUP BY
</code>
, see
<a class="xref" href="group-by-handling.html" title="14.19.3 MySQL Handling of GROUP BY">
Section 14.19.3, “MySQL Handling of GROUP BY”
</a>
.) In this case, the server
is free to choose any value from this nonaggregated column in
summary rows, and this includes the extra rows added by
<code class="literal">
WITH ROLLUP
</code>
. For example, in the following
query,
<code class="literal">
country
</code>
is a nonaggregated column
that does not appear in the
<code class="literal">
GROUP BY
</code>
list
and values chosen for this column are nondeterministic:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa68023766"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token datatype">year</span><span class="token punctuation">,</span> country<span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>profit<span class="token punctuation">)</span> <span class="token keyword">AS</span> profit
<span class="token keyword">FROM</span> sales
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token datatype">year</span> <span class="token keyword">WITH</span> <span class="token keyword">ROLLUP</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> year <span class="token punctuation">|</span> country <span class="token punctuation">|</span> profit <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> 4525 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> 3010 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> 7535 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
This behavior is permitted when the
<a class="link" href="sql-mode.html#sqlmode_only_full_group_by">
<code class="literal">
ONLY_FULL_GROUP_BY
</code>
</a>
SQL mode
is not enabled. If that mode is enabled, the server rejects
the query as illegal because
<code class="literal">
country
</code>
is not
listed in the
<code class="literal">
GROUP BY
</code>
clause. With
<a class="link" href="sql-mode.html#sqlmode_only_full_group_by">
<code class="literal">
ONLY_FULL_GROUP_BY
</code>
</a>
enabled,
you can still execute the query by using the
<a class="link" href="miscellaneous-functions.html#function_any-value">
<code class="literal">
ANY_VALUE()
</code>
</a>
function for
nondeterministic-value columns:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa22868350"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token datatype">year</span><span class="token punctuation">,</span> <span class="token function">ANY_VALUE</span><span class="token punctuation">(</span>country<span class="token punctuation">)</span> <span class="token keyword">AS</span> country<span class="token punctuation">,</span> <span class="token function">SUM</span><span class="token punctuation">(</span>profit<span class="token punctuation">)</span> <span class="token keyword">AS</span> profit
<span class="token keyword">FROM</span> sales
<span class="token keyword">GROUP</span> <span class="token keyword">BY</span> <span class="token datatype">year</span> <span class="token keyword">WITH</span> <span class="token keyword">ROLLUP</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> year <span class="token punctuation">|</span> country <span class="token punctuation">|</span> profit <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2000 <span class="token punctuation">|</span> India <span class="token punctuation">|</span> 4525 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2001 <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> 3010 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> USA <span class="token punctuation">|</span> 7535 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
A rollup column cannot be used as an argument to
<a class="link" href="fulltext-search.html#function_match">
<code class="literal">
MATCH()
</code>
</a>
(and is rejected with
an error) except when called in a
<code class="literal">
WHERE
</code>
clause. See
<a class="xref" href="fulltext-search.html" title="14.9 Full-Text Search Functions">
Section 14.9, “Full-Text Search Functions”
</a>
, for more
information.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/error-log-json.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="error-log-json">
</a>
7.4.2.7 Error Logging in JSON Format
</h4>
</div>
</div>
</div>
<p>
This section describes how to configure error logging using the
built-in filter,
<code class="literal">
log_filter_internal
</code>
, and the
JSON sink,
<code class="literal">
log_sink_json
</code>
, to take effect
immediately and for subsequent server startups. For general
information about configuring error logging, see
<a class="xref" href="error-log-configuration.html" title="7.4.2.1 Error Log Configuration">
Section 7.4.2.1, “Error Log Configuration”
</a>
.
</p>
<p>
To enable the JSON sink, first load the sink component, then
modify the
<a class="link" href="server-system-variables.html#sysvar_log_error_services">
<code class="literal">
log_error_services
</code>
</a>
value:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63246492"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">INSTALL</span> <span class="token keyword">COMPONENT</span> <span class="token string">'file://component_log_sink_json'</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">PERSIST</span> log_error_services <span class="token operator">=</span> <span class="token string">'log_filter_internal; log_sink_json'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To set
<a class="link" href="server-system-variables.html#sysvar_log_error_services">
<code class="literal">
log_error_services
</code>
</a>
to
take effect at server startup, use the instructions at
<a class="xref" href="error-log-configuration.html" title="7.4.2.1 Error Log Configuration">
Section 7.4.2.1, “Error Log Configuration”
</a>
. Those instructions
apply to other error-logging system variables as well.
</p>
<p>
It is permitted to name
<code class="literal">
log_sink_json
</code>
multiple times in the
<a class="link" href="server-system-variables.html#sysvar_log_error_services">
<code class="literal">
log_error_services
</code>
</a>
value. For
example, to write unfiltered events with one instance and
filtered events with another instance, you could set
<a class="link" href="server-system-variables.html#sysvar_log_error_services">
<code class="literal">
log_error_services
</code>
</a>
like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa97604783"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">PERSIST</span> log_error_services <span class="token operator">=</span> <span class="token string">'log_sink_json; log_filter_internal; log_sink_json'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The JSON sink determines its output destination based on the
default error log destination, which is given by the
<a class="link" href="server-system-variables.html#sysvar_log_error">
<code class="literal">
log_error
</code>
</a>
system variable. If
<a class="link" href="server-system-variables.html#sysvar_log_error">
<code class="literal">
log_error
</code>
</a>
names a file, the
JSON sink bases output file naming on that file name, plus a
numbered
<code class="filename">
.
<em class="replaceable">
<code>
NN
</code>
</em>
.json
</code>
suffix,
with
<em class="replaceable">
<code>
NN
</code>
</em>
starting at 00. For example,
if
<a class="link" href="server-system-variables.html#sysvar_log_error">
<code class="literal">
log_error
</code>
</a>
is
<em class="replaceable">
<code>
file_name
</code>
</em>
, successive instances of
<code class="literal">
log_sink_json
</code>
named in the
<a class="link" href="server-system-variables.html#sysvar_log_error_services">
<code class="literal">
log_error_services
</code>
</a>
value write
to
<code class="filename">
<em class="replaceable">
<code>
file_name
</code>
</em>
.00.json
</code>
,
<code class="filename">
<em class="replaceable">
<code>
file_name
</code>
</em>
.01.json
</code>
,
and so forth.
</p>
<p>
If
<a class="link" href="server-system-variables.html#sysvar_log_error">
<code class="literal">
log_error
</code>
</a>
is
<code class="literal">
stderr
</code>
, the JSON sink writes to the console.
If
<code class="literal">
log_sink_json
</code>
is named multiple times in
the
<a class="link" href="server-system-variables.html#sysvar_log_error_services">
<code class="literal">
log_error_services
</code>
</a>
value,
they all write to the console, which is likely not useful.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-limitations.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysql-cluster-limitations">
</a>
25.2.7 Known Limitations of NDB Cluster
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="mysql-cluster-limitations-syntax.html">
25.2.7.1 Noncompliance with SQL Syntax in NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations-limits.html">
25.2.7.2 Limits and Differences of NDB Cluster from Standard MySQL Limits
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations-transactions.html">
25.2.7.3 Limits Relating to Transaction Handling in NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations-error-handling.html">
25.2.7.4 NDB Cluster Error Handling
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations-database-objects.html">
25.2.7.5 Limits Associated with Database Objects in NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations-unsupported.html">
25.2.7.6 Unsupported or Missing Features in NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations-performance.html">
25.2.7.7 Limitations Relating to Performance in NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations-exclusive-to-cluster.html">
25.2.7.8 Issues Exclusive to NDB Cluster
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations-disk-data.html">
25.2.7.9 Limitations Relating to NDB Cluster Disk Data Storage
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations-multiple-nodes.html">
25.2.7.10 Limitations Relating to Multiple NDB Cluster Nodes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-cluster-limitations-resolved.html">
25.2.7.11 Previous NDB Cluster Issues Resolved in NDB Cluster 8.4
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045123675120">
</a>
<a class="indexterm" name="idm46045123674048">
</a>
<p>
In the sections that follow, we discuss known limitations in
current releases of NDB Cluster as compared with the features
available when using the
<code class="literal">
MyISAM
</code>
and
<code class="literal">
InnoDB
</code>
storage engines. If you check the
<span class="quote">
“
<span class="quote">
Cluster
</span>
”
</span>
category in the MySQL bugs database at
<a class="ulink" href="http://bugs.mysql.com" target="_blank">
http://bugs.mysql.com
</a>
, you can find known bugs in
the following categories under
<span class="quote">
“
<span class="quote">
MySQL Server:
</span>
”
</span>
in the
MySQL bugs database at
<a class="ulink" href="http://bugs.mysql.com" target="_blank">
http://bugs.mysql.com
</a>
, which
we intend to correct in upcoming releases of NDB Cluster:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
NDB Cluster
</p>
</li>
<li class="listitem">
<p>
Cluster Direct API (NDBAPI)
</p>
</li>
<li class="listitem">
<p>
Cluster Disk Data
</p>
</li>
<li class="listitem">
<p>
Cluster Replication
</p>
</li>
<li class="listitem">
<p>
ClusterJ
</p>
</li>
</ul>
</div>
<p>
This information is intended to be complete with respect to the
conditions just set forth. You can report any discrepancies that
you encounter to the MySQL bugs database using the instructions
given in
<a class="xref" href="bug-reports.html" title="1.6 How to Report Bugs or Problems">
Section 1.6, “How to Report Bugs or Problems”
</a>
. Any problem which we do
not plan to fix in NDB Cluster 8.4, is added to the
list.
</p>
<p>
See
<a class="xref" href="mysql-cluster-limitations-resolved.html" title="25.2.7.11 Previous NDB Cluster Issues Resolved in NDB Cluster 8.4">
Section 25.2.7.11, “Previous NDB Cluster Issues Resolved in NDB Cluster 8.4”
</a>
for a
list of issues in earlier releases that have been resolved in NDB
Cluster 8.4.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Limitations and other issues specific to NDB Cluster Replication
are described in
<a class="xref" href="mysql-cluster-replication-issues.html" title="25.7.3 Known Issues in NDB Cluster Replication">
Section 25.7.3, “Known Issues in NDB Cluster Replication”
</a>
.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/added-deprecated-removed.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="added-deprecated-removed">
</a>
1.5 Server and Status Variables and Options Added, Deprecated, or Removed in
MySQL 8.4 since 8.0
</h2>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="added-deprecated-removed.html#optvars-added" title="Options and Variables Introduced in MySQL 8.4">
Options and Variables Introduced in MySQL 8.4
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="added-deprecated-removed.html#optvars-deprecated" title="Options and Variables Deprecated in MySQL 8.4">
Options and Variables Deprecated in MySQL 8.4
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="added-deprecated-removed.html#optvars-removed" title="Options and Variables Removed in MySQL 8.4">
Options and Variables Removed in MySQL 8.4
</a>
</p>
</li>
</ul>
</div>
<p>
This section lists server variables, status variables, and options
that were added for the first time, have been deprecated, or have
been removed in MySQL 8.4 since 8.0.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="optvars-added">
</a>
Options and Variables Introduced in MySQL 8.4
</h3>
</div>
</div>
</div>
<p>
The following system variables, status variables, and server
options have been added in MySQL 8.4.
</p>
<div class="itemizedlist">
<a name="optvars-added-list">
</a>
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="audit-log-reference.html#statvar_Audit_log_direct_writes">
Audit_log_direct_writes
</a>
</code>
:
Number of direct writes to the audit log file. Added in MySQL
8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-status-variables.html#statvar_Com_xxx">
Com_show_binary_log_status
</a>
</code>
:
Count of SHOW BINARY LOG STATUS statements; use instead of
Com_show_master_status. Added in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-status-variables.html#statvar_Deprecated_use_i_s_processlist_count">
Deprecated_use_i_s_processlist_count
</a>
</code>
:
Number of times Information Schema processlist table has been
accessed. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-status-variables.html#statvar_Deprecated_use_i_s_processlist_last_timestamp">
Deprecated_use_i_s_processlist_last_timestamp
</a>
</code>
:
Time of most recent access to Information Schema processlist
table (timestamp). Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_all_consensus_proposals_count">
Gr_all_consensus_proposals_count
</a>
</code>
:
Sum of all proposals that were initiated and terminated in
this node. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_all_consensus_time_sum">
Gr_all_consensus_time_sum
</a>
</code>
:
The sum of elapsed time of all consensus rounds started and
finished in this node. Togheter with
count_all_consensus_proposals, we can identify if the
individual consensus time has a trend of going up, thus
signaling a possible problem. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_certification_garbage_collector_count">
Gr_certification_garbage_collector_count
</a>
</code>
:
Number of times certification garbage collection did run.
Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_certification_garbage_collector_time_sum">
Gr_certification_garbage_collector_time_sum
</a>
</code>
:
Sum of the time in micro-seconds that certification garbage
collection runs took. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_consensus_bytes_received_sum">
Gr_consensus_bytes_received_sum
</a>
</code>
:
The sum of all socket-level bytes that were received to from
group nodes having as a destination this node. Added in MySQL
8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_consensus_bytes_sent_sum">
Gr_consensus_bytes_sent_sum
</a>
</code>
:
Sum of all socket-level bytes that were sent to all group
nodes originating on this node. Socket-level bytes mean that
we will report more data here than in the sent messages,
because they are multiplexed and sent to each member. As an
example, if we have a group with 3 members and we send a 100
bytes message, this value will account for 300 bytes, since we
send 100 bytes to each node. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_control_messages_sent_bytes_sum">
Gr_control_messages_sent_bytes_sum
</a>
</code>
:
Sum of bytes of control messages sent by this member. The size
is the on-the-wire size. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_control_messages_sent_count">
Gr_control_messages_sent_count
</a>
</code>
:
Number of control messages sent by this member. Added in MySQL
8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_control_messages_sent_roundtrip_time_sum">
Gr_control_messages_sent_roundtrip_time_sum
</a>
</code>
:
Sum of the roundtrip time in micro-seconds of control messages
sent by this member. The time is measured between the send and
the delivery of the message on the sender member. This time
will measure the time between the send and the delivery of the
message on the majority of the members of the group (that
includes the sender). Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_data_messages_sent_bytes_sum">
Gr_data_messages_sent_bytes_sum
</a>
</code>
:
Sum of bytes of data messages sent by this member. The size is
the on-the-wire size. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_data_messages_sent_count">
Gr_data_messages_sent_count
</a>
</code>
:
Number of data messages sent by this member. Counts the number
of transaction data messages sent. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_data_messages_sent_roundtrip_time_sum">
Gr_data_messages_sent_roundtrip_time_sum
</a>
</code>
:
Sum of the roundtrip time in micro-seconds of data messages
sent by this member. The time is measured between the send and
the delivery of the message on the sender member. This time
will measure the time between the send and the delivery of the
message on the majority of the members of the group (that
includes the sender). Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_empty_consensus_proposals_count">
Gr_empty_consensus_proposals_count
</a>
</code>
:
Sum of all empty proposal rounds that were initiated and
terminated in this node. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_extended_consensus_count">
Gr_extended_consensus_count
</a>
</code>
:
The number of full 3-Phase PAXOS that this node initiated. If
this number grows, it means that at least of the node is
having issues answering to Proposals, either by slowliness or
network issues. Use togheter with
count_member_failure_suspicions to try and do some diagnose.
Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_last_consensus_end_timestamp">
Gr_last_consensus_end_timestamp
</a>
</code>
:
The time in which our last consensus proposal was approved.
Reported in a timestamp format. This is an indicator if the
group is halted or making slow progress. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_total_messages_sent_count">
Gr_total_messages_sent_count
</a>
</code>
:
The number of high-level messages that this node sent to the
group. These messages are the ones the we receive via the API
to be proposed to the group. XCom has a batching mechanism,
that will gather these messages and propose them all togheter.
This will acocunt the number of message before being batched.
Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_transactions_consistency_after_sync_count">
Gr_transactions_consistency_after_sync_count
</a>
</code>
:
Number of transactions on secondaries that waited to start,
while waiting for transactions from the primary with
group_replication_consistency= AFTER and BEFORE_AND_AFTER to
be committed. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_transactions_consistency_after_sync_time_sum">
Gr_transactions_consistency_after_sync_time_sum
</a>
</code>
:
Sum of the time in micro-seconds that transactions on
secondaries waited to start, while waiting for transactions
from the primary with group_replication_consistency= AFTER and
BEFORE_AND_AFTER to be committed. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_transactions_consistency_after_termination_count">
Gr_transactions_consistency_after_termination_count
</a>
</code>
:
Number of transactions executed with
group_replication_consistency= AFTER and BEFORE_AND_AFTER.
Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_transactions_consistency_after_termination_time_sum">
Gr_transactions_consistency_after_termination_time_sum
</a>
</code>
:
Sum of the time in micro-seconds spent between the delivery of
the transaction executed with
group_replication_consistency=AFTER and BEFORE_AND_AFTER, and
the acknowledge of the other group members that the
transaction is prepared. It does not include the transaction
send roundtrip time. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_transactions_consistency_before_begin_count">
Gr_transactions_consistency_before_begin_count
</a>
</code>
:
Number of transactions executed with
group_replication_consistency= BEFORE and BEFORE_AND_AFTER.
Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-status-variables.html#statvar_Gr_transactions_consistency_before_begin_time_sum">
Gr_transactions_consistency_before_begin_time_sum
</a>
</code>
:
Sum of the time in micro-seconds that the member waited until
its group_replication_applier channel was consumed before
execute the transaction with group_replication_consistency=
BEFORE and BEFORE_AND_AFTER. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_meter_lost">
Performance_schema_meter_lost
</a>
</code>
:
Number of meter instruments that failed to be created. Added
in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="performance-schema-status-variables.html#statvar_Performance_schema_metric_lost">
Performance_schema_metric_lost
</a>
</code>
:
Number of metric instruments that failed to be created. Added
in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-status-variables.html#statvar_Telemetry_metrics_supported">
Telemetry_metrics_supported
</a>
</code>
:
Whether server telemetry metrics is supported. Added in MySQL
8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-status-variables.html#statvar_Tls_sni_server_name">
Tls_sni_server_name
</a>
</code>
:
Server name supplied by the client. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="pluggable-authentication-system-variables.html#sysvar_authentication_ldap_sasl_connect_timeout">
authentication_ldap_sasl_connect_timeout
</a>
</code>
:
SASL-Based LDAP server connection timeout. Added in MySQL
8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="pluggable-authentication-system-variables.html#sysvar_authentication_ldap_sasl_response_timeout">
authentication_ldap_sasl_response_timeout
</a>
</code>
:
Simple LDAP server response timeout. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="pluggable-authentication-system-variables.html#sysvar_authentication_ldap_simple_connect_timeout">
authentication_ldap_simple_connect_timeout
</a>
</code>
:
Simple LDAP server connection timeout. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="pluggable-authentication-system-variables.html#sysvar_authentication_ldap_simple_response_timeout">
authentication_ldap_simple_response_timeout
</a>
</code>
:
Simple LDAP server response timeout. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="pluggable-authentication-system-variables.html#sysvar_authentication_webauthn_rp_id">
authentication_webauthn_rp_id
</a>
</code>
:
Relying party ID for multifactor authentication. Added in
MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="data-masking-component-variables.html#sysvar_component_masking.dictionaries_flush_interval_seconds">
component_masking.dictionaries_flush_interval_seconds
</a>
</code>
:
How long for scheduler to wait until attempting to schedule
next execution, in seconds. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="data-masking-component-variables.html#sysvar_component_masking.masking_database">
component_masking.masking_database
</a>
</code>
:
Database to use for masking dictionaries. Added in MySQL
8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_preemptive_garbage_collection">
group_replication_preemptive_garbage_collection
</a>
</code>
:
Enable preemptive garbage collection in single-primary mode;
no effect in multi-primary mode. Added in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_preemptive_garbage_collection_rows_threshold">
group_replication_preemptive_garbage_collection_rows_threshold
</a>
</code>
:
Number of rows of certification information required to
trigger preemptive garbage collection in single-primary mode
when enabled by
group_replication_preemptive_garbage_collection. Added in
MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="keyring-options.html#option_mysqld_keyring-migration-from-component">
keyring-migration-from-component
</a>
</code>
:
Keyring migration is from component to plugin. Added in MySQL
8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-options.html#option_mysqld_mysql-native-password">
mysql-native-password
</a>
</code>
:
Enable mysql_native_password authentication plugin. Added in
MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="firewall-reference.html#sysvar_mysql_firewall_database">
mysql_firewall_database
</a>
</code>
:
The database from which MySQL Enterprise Firewall sources its
tables and stored procedures. Added in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="firewall-reference.html#sysvar_mysql_firewall_reload_interval_seconds">
mysql_firewall_reload_interval_seconds
</a>
</code>
:
Reload data at specified intervals. Added in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_meter_classes">
performance_schema_max_meter_classes
</a>
</code>
:
Maximum number of meter instruments which can be created.
Added in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_max_metric_classes">
performance_schema_max_metric_classes
</a>
</code>
:
Maximum number of metric instruments which can be created.
Added in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-system-variables.html#sysvar_restrict_fk_on_non_standard_key">
restrict_fk_on_non_standard_key
</a>
</code>
:
Disallow creation of foreign keys on non-unique or partial
keys. Added in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-system-variables.html#sysvar_set_operations_buffer_size">
set_operations_buffer_size
</a>
</code>
:
Amount of memory available for hashing of set operations.
Added in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-status-variables.html#statvar_telemetry.live_sessions">
telemetry.live_sessions
</a>
</code>
:
Displays the current number of sessions instrumented with
telemetry. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.metrics_reader_frequency_1">
telemetry.metrics_reader_frequency_1
</a>
</code>
:
. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.metrics_reader_frequency_2">
telemetry.metrics_reader_frequency_2
</a>
</code>
:
. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.metrics_reader_frequency_3">
telemetry.metrics_reader_frequency_3
</a>
</code>
:
. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_bsp_max_export_batch_size">
telemetry.otel_bsp_max_export_batch_size
</a>
</code>
:
Maximum batch size. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_bsp_max_queue_size">
telemetry.otel_bsp_max_queue_size
</a>
</code>
:
Maximum queue size. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_bsp_schedule_delay">
telemetry.otel_bsp_schedule_delay
</a>
</code>
:
Delay interval between two consecutive exports in
milliseconds. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_certificates">
telemetry.otel_exporter_otlp_metrics_certificates
</a>
</code>
:
The trusted certificate to use when verifying a server's TLS
credentials. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_cipher">
telemetry.otel_exporter_otlp_metrics_cipher
</a>
</code>
:
TLS cipher to use for metrics (TLS 1.2). Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_cipher_suite">
telemetry.otel_exporter_otlp_metrics_cipher_suite
</a>
</code>
:
TLS cipher to use for metrics (TLS 1.3). Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_client_certificates">
telemetry.otel_exporter_otlp_metrics_client_certificates
</a>
</code>
:
Client certificate/chain trust for clients private key in PEM
format. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_client_key">
telemetry.otel_exporter_otlp_metrics_client_key
</a>
</code>
:
Client's private key in PEM format. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_compression">
telemetry.otel_exporter_otlp_metrics_compression
</a>
</code>
:
Compression used by exporter. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_endpoint">
telemetry.otel_exporter_otlp_metrics_endpoint
</a>
</code>
:
Metrics endpoint URL. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_headers">
telemetry.otel_exporter_otlp_metrics_headers
</a>
</code>
:
Key-value pairs to be used as headers associated with HTTP
requests. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_min_tls">
telemetry.otel_exporter_otlp_metrics_max_tls
</a>
</code>
:
Maximum TLS version to use for metrics. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_min_tls">
telemetry.otel_exporter_otlp_metrics_min_tls
</a>
</code>
:
Minimum TLS version to use for metrics. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_protocol">
telemetry.otel_exporter_otlp_metrics_protocol
</a>
</code>
:
Specifies the OTLP transport protocol. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-metrics-configuration.html#sysvar_telemetry.otel_exporter_otlp_metrics_timeout">
telemetry.otel_exporter_otlp_metrics_timeout
</a>
</code>
:
Time OLTP exporter waits for each batch export. Added in MySQL
8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_certificates">
telemetry.otel_exporter_otlp_traces_certificates
</a>
</code>
:
The trusted certificate to use when verifying a server's TLS
credentials.. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_cipher">
telemetry.otel_exporter_otlp_traces_cipher
</a>
</code>
:
TLS cipher to use for traces (TLS 1.2). Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_cipher_suite">
telemetry.otel_exporter_otlp_traces_cipher_suite
</a>
</code>
:
TLS cipher to use for traces (TLS 1.3). Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_client_certificates">
telemetry.otel_exporter_otlp_traces_client_certificates
</a>
</code>
:
Client certificate/chain trust for clients private key in PEM
format.. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_client_key">
telemetry.otel_exporter_otlp_traces_client_key
</a>
</code>
:
Client's private key in PEM format.. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_compression">
telemetry.otel_exporter_otlp_traces_compression
</a>
</code>
:
Compression used by exporter. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_endpoint">
telemetry.otel_exporter_otlp_traces_endpoint
</a>
</code>
:
Target URL to which the exporter sends traces. Added in MySQL
8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_headers">
telemetry.otel_exporter_otlp_traces_headers
</a>
</code>
:
Key-value pairs to be used as headers associated with HTTP
requests. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_max_tls">
telemetry.otel_exporter_otlp_traces_max_tls
</a>
</code>
:
Maximum TLS version to use for traces. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_min_tls">
telemetry.otel_exporter_otlp_traces_min_tls
</a>
</code>
:
Minimum TLS version to use for traces. Added in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_protocol">
telemetry.otel_exporter_otlp_traces_protocol
</a>
</code>
:
OTLP transport protocol. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_exporter_otlp_traces_timeout">
telemetry.otel_exporter_otlp_traces_timeout
</a>
</code>
:
Time OLTP exporter waits for each batch export. Added in MySQL
8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_log_level">
telemetry.otel_log_level
</a>
</code>
:
Controls which opentelemetry logs are printed in the server
logs (Linux only). Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.otel_resource_attributes">
telemetry.otel_resource_attributes
</a>
</code>
:
See corresponding OpenTelemetry variable
OTEL_RESOURCE_ATTRIBUTES.. Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.query_text_enabled">
telemetry.query_text_enabled
</a>
</code>
:
Controls whether the SQL query text is included in the trace
(Linux only). Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="telemetry-trace-configuration.html#sysvar_telemetry.trace_enabled">
telemetry.trace_enabled
</a>
</code>
:
Controls whether telemetry traces are collected or not (Linux
only). Added in MySQL 8.1.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-system-variables.html#sysvar_thread_pool_longrun_trx_limit">
thread_pool_longrun_trx_limit
</a>
</code>
:
When all threads using thread_pool_max_transactions_limit have
been executing longer than this number of milliseconds, limit
for group is suspended. Added in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-system-variables.html#sysvar_tls_certificates_enforced_validation">
tls_certificates_enforced_validation
</a>
</code>
:
Whether to validate server and CA certificates. Added in MySQL
8.1.0.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="optvars-deprecated">
</a>
Options and Variables Deprecated in MySQL 8.4
</h3>
</div>
</div>
</div>
<p>
The following system variables, status variables, and options have
been deprecated in MySQL 8.4.
</p>
<div class="itemizedlist">
<a name="optvars-deprecated-list">
</a>
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
Com_show_master_status
</code>
: Count of SHOW
MASTER STATUS statements. Deprecated in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
authentication_fido_rp_id
</code>
: Relying party ID
for FIDO multifactor authentication. Deprecated in MySQL
8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
binlog_transaction_dependency_tracking
</code>
:
Source of dependency information (commit timestamps or
transaction write sets) from which to assess which
transactions can be executed in parallel by replica's
multithreaded applier. Deprecated in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="ulink" href="/doc/refman/8.0/en/server-options.html#option_mysqld_character-set-client-handshake" target="_top">
character-set-client-handshake
</a>
</code>
:
Do not ignore client side character set value sent during
handshake. Deprecated in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_allow_local_lower_version_join">
group_replication_allow_local_lower_version_join
</a>
</code>
:
Allow current server to join group even if it has lower plugin
version than group. Deprecated in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_view_change_uuid">
group_replication_view_change_uuid
</a>
</code>
:
UUID for view change event GTIDs. Deprecated in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-options.html#option_mysqld_mysql-native-password">
mysql-native-password
</a>
</code>
:
Enable mysql_native_password authentication plugin. Deprecated
in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
new
</code>
: Use very new, possibly 'unsafe'
functions. Deprecated in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
old
</code>
: Cause server to revert to certain
behaviors present in older versions. Deprecated in MySQL
8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="performance-schema-system-variables.html#sysvar_performance_schema_show_processlist">
performance_schema_show_processlist
</a>
</code>
:
Select SHOW PROCESSLIST implementation. Deprecated in MySQL
8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-system-variables.html#sysvar_restrict_fk_on_non_standard_key">
restrict_fk_on_non_standard_key
</a>
</code>
:
Disallow creation of foreign keys on non-unique or partial
keys. Deprecated in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="ulink" href="/doc/refman/8.0/en/server-options.html#option_mysqld_character-set-client-handshake" target="_top">
skip-character-set-client-handshake
</a>
</code>
:
Ignore client side character set value sent during handshake.
Deprecated in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-options.html#option_mysqld_skip-new">
skip-new
</a>
</code>
:
Do not use new, possibly wrong routines. Deprecated in MySQL
8.2.0.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="optvars-removed">
</a>
Options and Variables Removed in MySQL 8.4
</h3>
</div>
</div>
</div>
<p>
The following system variables, status variables, and options have
been removed in MySQL 8.4.
</p>
<div class="itemizedlist">
<a name="optvars-removed-list">
</a>
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
Com_change_master
</code>
: Count of CHANGE
REPLICATION SOURCE TO and CHANGE MASTER TO statements. Removed
in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
Com_show_master_status
</code>
: Count of SHOW
MASTER STATUS statements. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
Com_show_slave_hosts
</code>
: Count of SHOW
REPLICAS and SHOW SLAVE HOSTS statements. Removed in MySQL
8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
Com_show_slave_status
</code>
: Count of SHOW
REPLICA STATUS and SHOW SLAVE STATUS statements. Removed in
MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
Com_slave_start
</code>
: Count of START REPLICA and
START SLAVE statements. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
Com_slave_stop
</code>
: Count of STOP REPLICA and
STOP SLAVE statements. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
Replica_rows_last_search_algorithm_used
</code>
:
Search algorithm most recently used by this replica to locate
rows for row-based replication (index, table, or hash scan).
Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
abort-slave-event-count
</code>
: Option used by
mysql-test for debugging and testing of replication. Removed
in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
admin-ssl
</code>
: Enable connection encryption.
Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
authentication_fido_rp_id
</code>
: Relying party ID
for FIDO multifactor authentication. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
avoid_temporal_upgrade
</code>
: Whether ALTER TABLE
should upgrade pre-5.6.4 temporal columns. Removed in MySQL
8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
binlog_transaction_dependency_tracking
</code>
:
Source of dependency information (commit timestamps or
transaction write sets) from which to assess which
transactions can be executed in parallel by replica's
multithreaded applier. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
character-set-client-handshake
</code>
: Do not
ignore client side character set value sent during handshake.
Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
daemon_memcached_enable_binlog
</code>
: . Removed
in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
daemon_memcached_engine_lib_name
</code>
: Shared
library implementing InnoDB memcached plugin. Removed in MySQL
8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
daemon_memcached_engine_lib_path
</code>
: Directory
which contains shared library implementing InnoDB memcached
plugin. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
daemon_memcached_option
</code>
: Space-separated
options which are passed to underlying memcached daemon on
startup. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
daemon_memcached_r_batch_size
</code>
: Specifies
how many memcached read operations to perform before doing
COMMIT to start new transaction. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
daemon_memcached_w_batch_size
</code>
: Specifies
how many memcached write operations to perform before doing
COMMIT to start new transaction. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
default_authentication_plugin
</code>
: Default
authentication plugin. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
disconnect-slave-event-count
</code>
: Option used
by mysql-test for debugging and testing of replication.
Removed in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
expire_logs_days
</code>
: Purge binary logs after
this many days. Removed in MySQL 8.2.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
group_replication_ip_whitelist
</code>
: List of
hosts permitted to connect to group. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
group_replication_primary_member
</code>
: Primary
member UUID when group operates in single-primary mode. Empty
string if group is operating in multi-primary mode. Removed in
MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
group_replication_recovery_complete_at
</code>
:
Recovery policies when handling cached transactions after
state transfer. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
have_openssl
</code>
: Whether mysqld supports SSL
connections. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
have_ssl
</code>
: Whether mysqld supports SSL
connections. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb
</code>
: Enable InnoDB (if this version of
MySQL supports it). Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_api_bk_commit_interval
</code>
: How often to
auto-commit idle connections which use InnoDB memcached
interface, in seconds. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_api_disable_rowlock
</code>
: . Removed in
MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_api_enable_binlog
</code>
: Allows use of
InnoDB memcached plugin with MySQL binary log. Removed in
MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_api_enable_mdl
</code>
: Locks table used by
InnoDB memcached plugin, so that it cannot be dropped or
altered by DDL through SQL interface. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
innodb_api_trx_level
</code>
: Allows control of
transaction isolation level on queries processed by memcached
interface. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_encrypted_file_data
</code>
:
keyring_encrypted_file plugin data file. Removed in MySQL
8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_encrypted_file_password
</code>
:
keyring_encrypted_file plugin password. Removed in MySQL
8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_file_data
</code>
: keyring_file plugin data
file. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_ca_certificate
</code>
: CA certificate
file for peer authentication. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_compartment
</code>
: OCI compartment
OCID. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_encryption_endpoint
</code>
: OCI
encryption server endpoint. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_key_file
</code>
: OCI RSA private key
file. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_key_fingerprint
</code>
: OCI RSA
private key file fingerprint. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_management_endpoint
</code>
: OCI
management server endpoint. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_master_key
</code>
: OCI master key
OCID. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_secrets_endpoint
</code>
: OCI secrets
server endpoint. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_tenancy
</code>
: OCI tenancy OCID.
Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_user
</code>
: OCI user OCID. Removed in
MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_vaults_endpoint
</code>
: OCI vaults
server endpoint. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
keyring_oci_virtual_vault
</code>
: OCI vault OCID.
Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
language
</code>
: Client error messages in given
language. May be given as full path. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
log_bin_use_v1_row_events
</code>
: Whether server
is using version 1 binary log row events. Removed in MySQL
8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
master-info-file
</code>
: Location and name of file
that remembers source and where I/O replication thread is in
source's binary log. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
master_info_repository
</code>
: Whether to write
connection metadata repository, containing source information
and replication I/O thread location in source's binary log, to
file or table. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
new
</code>
: Use very new, possibly 'unsafe'
functions. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
no-dd-upgrade
</code>
: Prevent automatic upgrade of
data dictionary tables at startup. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
old
</code>
: Cause server to revert to certain
behaviors present in older versions. Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
old-style-user-limits
</code>
: Enable old-style
user limits (before 5.0.3, user resources were counted per
each user+host vs. per account). Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
relay_log_info_file
</code>
: File name for applier
metadata repository in which replica records information about
relay logs. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
relay_log_info_repository
</code>
: Whether to write
location of replication SQL thread in relay logs to file or
table. Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
show_old_temporals
</code>
: Whether SHOW CREATE
TABLE should indicate pre-5.6.4 temporal columns. Removed in
MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
skip-character-set-client-handshake
</code>
: Ignore
client side character set value sent during handshake. Removed
in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
skip-host-cache
</code>
: Do not cache host names.
Removed in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
skip-ssl
</code>
: Disable connection encryption.
Removed in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
slave_rows_search_algorithms
</code>
: Determines
search algorithms used for replica update batching. Any 2 or 3
from this list: INDEX_SEARCH, TABLE_SCAN, HASH_SCAN. Removed
in MySQL 8.3.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ssl
</code>
: Enable connection encryption. Removed
in MySQL 8.4.0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
transaction_write_set_extraction
</code>
: Defines
algorithm used to hash writes extracted during transaction.
Removed in MySQL 8.3.0.
</p>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/selinux-policies.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="selinux-policies">
</a>
8.7.3 MySQL Server SELinux Policies
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045231621552">
</a>
<p>
MySQL Server SELinux policy modules are typically installed by
default. You can view installed modules using the
<span class="command">
<strong>
semodule -l
</strong>
</span>
command. MySQL Server SELinux
policy modules include:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
mysqld_selinux
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
mysqld_safe_selinux
</code>
</p>
</li>
</ul>
</div>
<p>
For information about MySQL Server SELinux policy modules, refer
to the SELinux manual pages. The manual pages provide information
about types and Booleans associated with the MySQL service. Manual
pages are named in the
<code class="literal">
<em class="replaceable">
<code>
service-name
</code>
</em>
_selinux
</code>
format.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa66526400"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">man mysqld_selinux</code></pre>
</div>
<p>
If SELinux manual pages are not available, refer to your
distribution's SELinux documentation for information about how to
generate manual pages using the
<code class="literal">
sepolicy
manpage
</code>
utility.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-administration-pausing.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-administration-pausing">
</a>
19.1.7.2 Pausing Replication on the Replica
</h4>
</div>
</div>
</div>
<p>
You can stop and start replication on the replica using the
<a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement">
<code class="literal">
STOP REPLICA
</code>
</a>
and
<a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement">
<code class="literal">
START REPLICA
</code>
</a>
statements.
</p>
<p>
To stop processing of the binary log from the source, use
<a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement">
<code class="literal">
STOP REPLICA
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa73992186"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">STOP</span> <span class="token keyword">REPLICA</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
When replication is stopped, the replication I/O (receiver)
thread stops reading events from the source binary log and
writing them to the relay log, and the SQL thread stops reading
events from the relay log and executing them. You can pause the
I/O (receiver) or SQL (applier) thread individually by
specifying the thread type:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16640149"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">STOP</span> <span class="token keyword">REPLICA</span> <span class="token keyword">IO_THREAD</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">STOP</span> <span class="token keyword">REPLICA</span> <span class="token keyword">SQL_THREAD</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To start execution again, use the
<a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement">
<code class="literal">
START
REPLICA
</code>
</a>
statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa45707296"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">START</span> <span class="token keyword">REPLICA</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To start a particular thread, specify the thread type:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa79435392"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">START</span> <span class="token keyword">REPLICA</span> <span class="token keyword">IO_THREAD</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">START</span> <span class="token keyword">REPLICA</span> <span class="token keyword">SQL_THREAD</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For a replica that performs updates only by processing events
from the source, stopping only the SQL thread can be useful if
you want to perform a backup or other task. The I/O (receiver)
thread continues to read events from the source but they are not
executed. This makes it easier for the replica to catch up when
you restart the SQL (applier) thread.
</p>
<p>
Stopping only the receiver thread enables the events in the
relay log to be executed by the applier thread up to the point
where the relay log ends. This can be useful when you want to
pause execution to catch up with events already received from
the source, when you want to perform administration on the
replica but also ensure that it has processed all updates to a
specific point. This method can also be used to pause event
receipt on the replica while you conduct administration on the
source. Stopping the receiver thread but permitting the applier
thread to run helps ensure that there is not a massive backlog
of events to be executed when replication is started again.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysqldump-upgrade-testing.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysqldump-upgrade-testing">
</a>
9.4.5.5 Using mysqldump to Test for Upgrade Incompatibilities
</h4>
</div>
</div>
</div>
<p>
When contemplating a MySQL upgrade, it is prudent to install
the newer version separately from your current production
version. Then you can dump the database and database object
definitions from the production server and load them into the
new server to verify that they are handled properly. (This is
also useful for testing downgrades.)
</p>
<p>
On the production server:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa85696290"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysqldump</span> <span class="token property">--all-databases</span> <span class="token property">--no-data</span> <span class="token property">--routines</span> <span class="token property">--events</span> > dump-defs<span class="token punctuation">.</span>sql</code></pre>
</div>
<p>
On the upgraded server:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa67355578"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysql</span> < dump-defs<span class="token punctuation">.</span>sql</code></pre>
</div>
<p>
Because the dump file does not contain table data, it can be
processed quickly. This enables you to spot potential
incompatibilities without waiting for lengthy data-loading
operations. Look for warnings or errors while the dump file is
being processed.
</p>
<p>
After you have verified that the definitions are handled
properly, dump the data and try to load it into the upgraded
server.
</p>
<p>
On the production server:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa53118777"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysqldump</span> <span class="token property">--all-databases</span> <span class="token property">--no-create-info</span> > dump-data<span class="token punctuation">.</span>sql</code></pre>
</div>
<p>
On the upgraded server:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa86573529"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysql</span> < dump-data<span class="token punctuation">.</span>sql</code></pre>
</div>
<p>
Now check the table contents and run some test queries.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/server-administration.html | <div id="docs-body">
<div class="chapter">
<div class="titlepage">
<div>
<div>
<h1 class="title">
<a name="server-administration">
</a>
Chapter 7 MySQL Server Administration
</h1>
</div>
</div>
</div>
<div class="toc">
<p>
<b>
Table of Contents
</b>
</p>
<dl class="toc">
<dt>
<span class="section">
<a href="mysqld-server.html">
7.1 The MySQL Server
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="server-configuration.html">
7.1.1 Configuring the Server
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-configuration-defaults.html">
7.1.2 Server Configuration Defaults
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-configuration-validation.html">
7.1.3 Server Configuration Validation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-option-variable-reference.html">
7.1.4 Server Option, System Variable, and Status Variable Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-system-variable-reference.html">
7.1.5 Server System Variable Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-status-variable-reference.html">
7.1.6 Server Status Variable Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-options.html">
7.1.7 Server Command Options
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-system-variables.html">
7.1.8 Server System Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="using-system-variables.html">
7.1.9 Using System Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-status-variables.html">
7.1.10 Server Status Variables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="sql-mode.html">
7.1.11 Server SQL Modes
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="connection-management.html">
7.1.12 Connection Management
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ipv6-support.html">
7.1.13 IPv6 Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="network-namespace-support.html">
7.1.14 Network Namespace Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="time-zone-support.html">
7.1.15 MySQL Server Time Zone Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="resource-groups.html">
7.1.16 Resource Groups
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-side-help-support.html">
7.1.17 Server-Side Help Support
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="session-state-tracking.html">
7.1.18 Server Tracking of Client Session State
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-shutdown.html">
7.1.19 The Server Shutdown Process
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="data-directory.html">
7.2 The MySQL Data Directory
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="system-schema.html">
7.3 The mysql System Schema
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="server-logs.html">
7.4 MySQL Server Logs
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="log-destinations.html">
7.4.1 Selecting General Query Log and Slow Query Log Output Destinations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="error-log.html">
7.4.2 The Error Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="query-log.html">
7.4.3 The General Query Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="binary-log.html">
7.4.4 The Binary Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="slow-query-log.html">
7.4.5 The Slow Query Log
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="log-file-maintenance.html">
7.4.6 Server Log Maintenance
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="components.html">
7.5 MySQL Components
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="component-loading.html">
7.5.1 Installing and Uninstalling Components
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="obtaining-component-information.html">
7.5.2 Obtaining Component Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="error-log-components.html">
7.5.3 Error Log Components
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="query-attribute-components.html">
7.5.4 Query Attribute Components
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="scheduler-component.html">
7.5.5 Scheduler Component
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="server-plugins.html">
7.6 MySQL Server Plugins
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="plugin-loading.html">
7.6.1 Installing and Uninstalling Plugins
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="obtaining-plugin-information.html">
7.6.2 Obtaining Server Plugin Information
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="thread-pool.html">
7.6.3 MySQL Enterprise Thread Pool
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="rewriter-query-rewrite-plugin.html">
7.6.4 The Rewriter Query Rewrite Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="ddl-rewriter.html">
7.6.5 The ddl_rewriter Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="version-tokens.html">
7.6.6 Version Tokens
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="clone-plugin.html">
7.6.7 The Clone Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="daemon-keyring-proxy-plugin.html">
7.6.8 The Keyring Proxy Bridge Plugin
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="plugin-services.html">
7.6.9 MySQL Plugin Services
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="server-loadable-functions.html">
7.7 MySQL Server Loadable Functions
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="function-loading.html">
7.7.1 Installing and Uninstalling Loadable Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="obtaining-loadable-function-information.html">
7.7.2 Obtaining Information About Loadable Functions
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="multiple-servers.html">
7.8 Running Multiple MySQL Instances on One Machine
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="multiple-data-directories.html">
7.8.1 Setting Up Multiple Data Directories
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="multiple-windows-servers.html">
7.8.2 Running Multiple MySQL Instances on Windows
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="multiple-unix-servers.html">
7.8.3 Running Multiple MySQL Instances on Unix
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="multiple-server-clients.html">
7.8.4 Using Client Programs in a Multiple-Server Environment
</a>
</span>
</dt>
</dl>
</dd>
<dt>
<span class="section">
<a href="debugging-mysql.html">
7.9 Debugging MySQL
</a>
</span>
</dt>
<dd>
<dl>
<dt>
<span class="section">
<a href="debugging-server.html">
7.9.1 Debugging a MySQL Server
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="debugging-client.html">
7.9.2 Debugging a MySQL Client
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="lock-order-tool.html">
7.9.3 The LOCK_ORDER Tool
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="dbug-package.html">
7.9.4 The DBUG Package
</a>
</span>
</dt>
</dl>
</dd>
</dl>
</div>
<p>
MySQL Server (
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
) is the main program that
does most of the work in a MySQL installation. This chapter provides
an overview of MySQL Server and covers general server
administration:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Server configuration
</p>
</li>
<li class="listitem">
<p>
The data directory, particularly the
<code class="literal">
mysql
</code>
system schema
</p>
</li>
<li class="listitem">
<p>
The server log files
</p>
</li>
<li class="listitem">
<p>
Management of multiple servers on a single machine
</p>
</li>
</ul>
</div>
<p>
For additional information on administrative topics, see also:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="security.html" title="Chapter 8 Security">
Chapter 8,
<i>
Security
</i>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="backup-and-recovery.html" title="Chapter 9 Backup and Recovery">
Chapter 9,
<i>
Backup and Recovery
</i>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="replication.html" title="Chapter 19 Replication">
Chapter 19,
<i>
Replication
</i>
</a>
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/encryption-functions.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="encryption-functions">
</a>
14.13 Encryption and Compression Functions
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045199614576">
</a>
<a class="indexterm" name="idm46045199613536">
</a>
<div class="table">
<a name="idm46045199612048">
</a>
<p class="title">
<b>
Table 14.18 Encryption Functions
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists encryption functions.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
</td>
<td>
Decrypt using AES
</td>
</tr>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
</td>
<td>
Encrypt using AES
</td>
</tr>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_compress">
<code class="literal">
COMPRESS()
</code>
</a>
</td>
<td>
Return result as a binary string
</td>
</tr>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_md5">
<code class="literal">
MD5()
</code>
</a>
</td>
<td>
Calculate MD5 checksum
</td>
</tr>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_random-bytes">
<code class="literal">
RANDOM_BYTES()
</code>
</a>
</td>
<td>
Return a random byte vector
</td>
</tr>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_sha1">
<code class="literal">
SHA1()
</code>
,
<code class="literal">
SHA()
</code>
</a>
</td>
<td>
Calculate an SHA-1 160-bit checksum
</td>
</tr>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_sha2">
<code class="literal">
SHA2()
</code>
</a>
</td>
<td>
Calculate an SHA-2 checksum
</td>
</tr>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_statement-digest">
<code class="literal">
STATEMENT_DIGEST()
</code>
</a>
</td>
<td>
Compute statement digest hash value
</td>
</tr>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_statement-digest-text">
<code class="literal">
STATEMENT_DIGEST_TEXT()
</code>
</a>
</td>
<td>
Compute normalized statement digest
</td>
</tr>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_uncompress">
<code class="literal">
UNCOMPRESS()
</code>
</a>
</td>
<td>
Uncompress a string compressed
</td>
</tr>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_uncompressed-length">
<code class="literal">
UNCOMPRESSED_LENGTH()
</code>
</a>
</td>
<td>
Return the length of a string before compression
</td>
</tr>
<tr>
<td>
<a class="link" href="encryption-functions.html#function_validate-password-strength">
<code class="literal">
VALIDATE_PASSWORD_STRENGTH()
</code>
</a>
</td>
<td>
Determine strength of password
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 739px;">
<thead>
<tr>
<th style="width: 234.516px;">
Name
</th>
<th style="width: 503.484px;">
Description
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
<p>
Many encryption and compression functions return strings for which
the result might contain arbitrary byte values. If you want to
store these results, use a column with a
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
VARBINARY
</code>
</a>
or
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
binary string data type. This
avoids potential problems with trailing space removal or character
set conversion that would change data values, such as may occur if
you use a nonbinary string data type
(
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
,
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
).
</p>
<p>
Some encryption functions return strings of ASCII characters:
<a class="link" href="encryption-functions.html#function_md5">
<code class="literal">
MD5()
</code>
</a>
,
<a class="link" href="encryption-functions.html#function_sha1">
<code class="literal">
SHA()
</code>
</a>
,
<a class="link" href="encryption-functions.html#function_sha1">
<code class="literal">
SHA1()
</code>
</a>
,
<a class="link" href="encryption-functions.html#function_sha2">
<code class="literal">
SHA2()
</code>
</a>
,
<a class="link" href="encryption-functions.html#function_statement-digest">
<code class="literal">
STATEMENT_DIGEST()
</code>
</a>
,
<a class="link" href="encryption-functions.html#function_statement-digest-text">
<code class="literal">
STATEMENT_DIGEST_TEXT()
</code>
</a>
. Their
return value is a string that has a character set and collation
determined by the
<a class="link" href="server-system-variables.html#sysvar_character_set_connection">
<code class="literal">
character_set_connection
</code>
</a>
and
<a class="link" href="server-system-variables.html#sysvar_collation_connection">
<code class="literal">
collation_connection
</code>
</a>
system
variables. This is a nonbinary string unless the character set is
<code class="literal">
binary
</code>
.
</p>
<p>
If an application stores values from a function such as
<a class="link" href="encryption-functions.html#function_md5">
<code class="literal">
MD5()
</code>
</a>
or
<a class="link" href="encryption-functions.html#function_sha1">
<code class="literal">
SHA1()
</code>
</a>
that returns a string of hex
digits, more efficient storage and comparisons can be obtained by
converting the hex representation to binary using
<a class="link" href="string-functions.html#function_unhex">
<code class="literal">
UNHEX()
</code>
</a>
and storing the result in a
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
BINARY(
<em class="replaceable">
<code>
N
</code>
</em>
)
</code>
</a>
column. Each pair of hexadecimal digits requires one byte in
binary form, so the value of
<em class="replaceable">
<code>
N
</code>
</em>
depends
on the length of the hex string.
<em class="replaceable">
<code>
N
</code>
</em>
is
16 for an
<a class="link" href="encryption-functions.html#function_md5">
<code class="literal">
MD5()
</code>
</a>
value and 20 for a
<a class="link" href="encryption-functions.html#function_sha1">
<code class="literal">
SHA1()
</code>
</a>
value. For
<a class="link" href="encryption-functions.html#function_sha2">
<code class="literal">
SHA2()
</code>
</a>
,
<em class="replaceable">
<code>
N
</code>
</em>
ranges from 28 to 32 depending on the
argument specifying the desired bit length of the result.
</p>
<p>
The size penalty for storing the hex string in a
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
column is at least two times,
up to eight times if the value is stored in a column that uses the
<code class="literal">
utf8mb4
</code>
character set (where each character
uses 4 bytes). Storing the string also results in slower
comparisons because of the larger values and the need to take
character set collation rules into account.
</p>
<p>
Suppose that an application stores
<a class="link" href="encryption-functions.html#function_md5">
<code class="literal">
MD5()
</code>
</a>
string values in a
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR(32)
</code>
</a>
column:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa25439234"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> md5_tbl <span class="token punctuation">(</span>md5_val <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">32</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> md5_tbl <span class="token punctuation">(</span>md5_val<span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span> <span class="token keyword">VALUES</span><span class="token punctuation">(</span><span class="token function">MD5</span><span class="token punctuation">(</span><span class="token string">'abcdef'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To convert hex strings to more compact form, modify the
application to use
<a class="link" href="string-functions.html#function_unhex">
<code class="literal">
UNHEX()
</code>
</a>
and
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
BINARY(16)
</code>
</a>
instead as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa28295470"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> md5_tbl <span class="token punctuation">(</span>md5_val <span class="token datatype">BINARY</span><span class="token punctuation">(</span><span class="token number">16</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> md5_tbl <span class="token punctuation">(</span>md5_val<span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span> <span class="token keyword">VALUES</span><span class="token punctuation">(</span><span class="token function">UNHEX</span><span class="token punctuation">(</span><span class="token function">MD5</span><span class="token punctuation">(</span><span class="token string">'abcdef'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Applications should be prepared to handle the very rare case that
a hashing function produces the same value for two different input
values. One way to make collisions detectable is to make the hash
column a primary key.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Exploits for the MD5 and SHA-1 algorithms have become known. You
may wish to consider using another one-way encryption function
described in this section instead, such as
<a class="link" href="encryption-functions.html#function_sha2">
<code class="literal">
SHA2()
</code>
</a>
.
</p>
</div>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Caution
</div>
<p>
Passwords or other sensitive values supplied as arguments to
encryption functions are sent as cleartext to the MySQL server
unless an SSL connection is used. Also, such values appear in
any MySQL logs to which they are written. To avoid these types
of exposure, applications can encrypt sensitive values on the
client side before sending them to the server. The same
considerations apply to encryption keys. To avoid exposing
these, applications can use stored procedures to encrypt and
decrypt values on the server side.
</p>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<a name="function_aes-decrypt">
</a>
<p>
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT(
<em class="replaceable">
<code>
crypt_str
</code>
</em>
,
<em class="replaceable">
<code>
key_str
</code>
</em>
[,
<em class="replaceable">
<code>
init_vector
</code>
</em>
][,
<em class="replaceable">
<code>
kdf_name
</code>
</em>
][,
<em class="replaceable">
<code>
salt
</code>
</em>
][,
<em class="replaceable">
<code>
info
| iterations
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045199517136">
</a>
<p>
This function decrypts data using the official AES (Advanced
Encryption Standard) algorithm. For more information, see the
description of
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
.
</p>
<p>
Statements that use
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
are unsafe for
statement-based replication.
</p>
</li>
<li class="listitem">
<a name="function_aes-encrypt">
</a>
<p>
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT(
<em class="replaceable">
<code>
str
</code>
</em>
,
<em class="replaceable">
<code>
key_str
</code>
</em>
[,
<em class="replaceable">
<code>
init_vector
</code>
</em>
][,
<em class="replaceable">
<code>
kdf_name
</code>
</em>
][,
<em class="replaceable">
<code>
salt
</code>
</em>
][,
<em class="replaceable">
<code>
info
| iterations
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045199504032">
</a>
<p>
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
and
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
implement
encryption and decryption of data using the official AES
(Advanced Encryption Standard) algorithm, previously known as
<span class="quote">
“
<span class="quote">
Rijndael.
</span>
”
</span>
The AES standard permits various key
lengths. By default these functions implement AES with a
128-bit key length. Key lengths of 196 or 256 bits can be
used, as described later. The key length is a trade off
between performance and security.
</p>
<p>
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
encrypts the
string
<em class="replaceable">
<code>
str
</code>
</em>
using the key string
<em class="replaceable">
<code>
key_str
</code>
</em>
, and returns a binary
string containing the encrypted output.
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
decrypts the
encrypted string
<em class="replaceable">
<code>
crypt_str
</code>
</em>
using
the key string
<em class="replaceable">
<code>
key_str
</code>
</em>
, and returns
the original (binary) string in hexadecimal format. (To obtain
the string as plaintext, cast the result to
<code class="literal">
CHAR
</code>
. Alternatively, start the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client with
<a class="link" href="mysql-command-options.html#option_mysql_binary-as-hex">
<code class="option">
--skip-binary-as-hex
</code>
</a>
to cause all binary values to be displayed as text.) If either
function argument is
<code class="literal">
NULL
</code>
, the function
returns
<code class="literal">
NULL
</code>
. If
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
detects invalid
data or incorrect padding, it returns
<code class="literal">
NULL
</code>
.
However, it is possible for
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
to return a
non-
<code class="literal">
NULL
</code>
value (possibly garbage) if the
input data or the key is invalid.
</p>
<p>
These functions support the use of a key derivation function
(KDF) to create a cryptographically strong secret key from the
information passed in
<em class="replaceable">
<code>
key_str
</code>
</em>
. The
derived key is used to encrypt and decrypt the data, and it
remains in the MySQL Server instance and is not accessible to
users. Using a KDF is highly recommended, as it provides
better security than specifying your own premade key or
deriving it by a simpler method as you use the function. The
functions support HKDF (available from OpenSSL 1.1.0), for
which you can specify an optional salt and context-specific
information to include in the keying material, and PBKDF2
(available from OpenSSL 1.0.2), for which you can specify an
optional salt and set the number of iterations used to produce
the key.
</p>
<p>
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
and
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
permit control of
the block encryption mode. The
<a class="link" href="server-system-variables.html#sysvar_block_encryption_mode">
<code class="literal">
block_encryption_mode
</code>
</a>
system
variable controls the mode for block-based encryption
algorithms. Its default value is
<code class="literal">
aes-128-ecb
</code>
, which signifies encryption
using a key length of 128 bits and ECB mode. For a description
of the permitted values of this variable, see
<a class="xref" href="server-system-variables.html" title="7.1.8 Server System Variables">
Section 7.1.8, “Server System Variables”
</a>
. The optional
<em class="replaceable">
<code>
init_vector
</code>
</em>
argument is used to
provide an initialization vector for block encryption modes
that require it.
</p>
<p>
Statements that use
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
or
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
are unsafe for
statement-based replication.
</p>
<p>
If
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
is invoked
from within the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client, binary
strings display using hexadecimal notation, depending on the
value of the
<a class="link" href="mysql-command-options.html#option_mysql_binary-as-hex">
<code class="option">
--binary-as-hex
</code>
</a>
.
For more information about that option, see
<a class="xref" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
Section 6.5.1, “mysql — The MySQL Command-Line Client”
</a>
.
</p>
<p>
The arguments for the
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
and
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
functions are as
follows:
</p>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<em class="replaceable">
<code>
str
</code>
</em>
</span>
</dt>
<dd>
<p>
The string for
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
to encrypt
using the key string
<em class="replaceable">
<code>
key_str
</code>
</em>
,
or the key derived from it by the specified KDF. The
string can be any length. Padding is automatically added
to
<em class="replaceable">
<code>
str
</code>
</em>
so it is a multiple of
a block as required by block-based algorithms such as
AES. This padding is automatically removed by the
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
function.
</p>
</dd>
<dt>
<span class="term">
<em class="replaceable">
<code>
crypt_str
</code>
</em>
</span>
</dt>
<dd>
<p>
The encrypted string for
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
to decrypt
using the key string
<em class="replaceable">
<code>
key_str
</code>
</em>
,
or the key derived from it by the specified KDF. The
string can be any length. The length of
<em class="replaceable">
<code>
crypt_str
</code>
</em>
can be calculated
from the length of the original string using this
formula:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-clike"><div class="docs-select-all right" id="sa73279735"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token number">16</span> <span class="token operator">*</span> <span class="token punctuation">(</span><span class="token function">trunc</span><span class="token punctuation">(</span><em class="replaceable">string_length</em> <span class="token operator">/</span> <span class="token number">16</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">)</span></code></pre>
</div>
</dd>
<dt>
<span class="term">
<em class="replaceable">
<code>
key_str
</code>
</em>
</span>
</dt>
<dd>
<p>
The encryption key, or the input keying material that is
used as the basis for deriving a key using a key
derivation function (KDF). For the same instance of
data, use the same value of
<em class="replaceable">
<code>
key_str
</code>
</em>
for encryption with
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
and
decryption with
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
.
</p>
<p>
If you are using a KDF,
<em class="replaceable">
<code>
key_str
</code>
</em>
can be any arbitrary
information such as a password or passphrase. In the
further arguments for the function, you specify the KDF
name, then add further options to increase the security
as appropriate for the KDF.
</p>
<p>
When you use a KDF, the function creates a
cryptographically strong secret key from the information
passed in
<em class="replaceable">
<code>
key_str
</code>
</em>
and any
salt or additional information that you provide in the
other arguments. The derived key is used to encrypt and
decrypt the data, and it remains in the MySQL Server
instance and is not accessible to users. Using a KDF is
highly recommended, as it provides better security than
specifying your own premade key or deriving it by a
simpler method as you use the function.
</p>
<p>
If you are not using a KDF, for a key length of 128
bits, the most secure way to pass a key to the
<em class="replaceable">
<code>
key_str
</code>
</em>
argument is to create
a truly random 128-bit value and pass it as a binary
value. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa11696982"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t
<span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token function">AES_ENCRYPT</span><span class="token punctuation">(</span><span class="token string">'text'</span><span class="token punctuation">,</span><span class="token function">UNHEX</span><span class="token punctuation">(</span><span class="token string">'F3229A0B371ED2D9441B830D21A390C3'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
A passphrase can be used to generate an AES key by
hashing the passphrase. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34738136"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t
<span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token function">AES_ENCRYPT</span><span class="token punctuation">(</span><span class="token string">'text'</span><span class="token punctuation">,</span> <span class="token function">UNHEX</span><span class="token punctuation">(</span><span class="token function">SHA2</span><span class="token punctuation">(</span><span class="token string">'My secret passphrase'</span><span class="token punctuation">,</span><span class="token number">512</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If you exceed the maximum key length of 128 bits, a
warning is returned. If you are not using a KDF, do not
pass a password or passphrase directly to
<em class="replaceable">
<code>
key_str
</code>
</em>
, hash it first.
Previous versions of this documentation suggested the
former approach, but it is no longer recommended as the
examples shown here are more secure.
</p>
</dd>
<dt>
<span class="term">
<em class="replaceable">
<code>
init_vector
</code>
</em>
</span>
</dt>
<dd>
<p>
An initialization vector, for block encryption modes
that require it. The
<a class="link" href="server-system-variables.html#sysvar_block_encryption_mode">
<code class="literal">
block_encryption_mode
</code>
</a>
system variable controls the mode. For the same instance
of data, use the same value of
<em class="replaceable">
<code>
init_vector
</code>
</em>
for encryption
with
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
and
decryption with
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If you are using a KDF, you must specify an
initialization vector or a null string for this
argument, in order to access the later arguments to
define the KDF.
</p>
</div>
<p>
For modes that require an initialization vector, it must
be 16 bytes or longer (bytes in excess of 16 are
ignored). An error occurs if
<em class="replaceable">
<code>
init_vector
</code>
</em>
is missing. For
modes that do not require an initialization vector, it
is ignored and a warning is generated if
<em class="replaceable">
<code>
init_vector
</code>
</em>
is specified,
unless you are using a KDF.
</p>
<p>
The default value for the
<a class="link" href="server-system-variables.html#sysvar_block_encryption_mode">
<code class="literal">
block_encryption_mode
</code>
</a>
system variable is
<code class="literal">
aes-128-ecb
</code>
, or
ECB mode, which does not require an initialization
vector. The alternative permitted block encryption modes
CBC, CFB1, CFB8, CFB128, and OFB all require an
initialization vector.
</p>
<p>
A random string of bytes to use for the initialization
vector can be produced by calling
<a class="link" href="encryption-functions.html#function_random-bytes">
<code class="literal">
RANDOM_BYTES(16)
</code>
</a>
.
</p>
</dd>
<dt>
<span class="term">
<em class="replaceable">
<code>
kdf_name
</code>
</em>
</span>
</dt>
<dd>
<p>
The name of the key derivation function (KDF) to create
a key from the input keying material passed in
<em class="replaceable">
<code>
key_str
</code>
</em>
, and other arguments
as appropriate for the KDF. Optional.
</p>
<p>
For the same instance of data, use the same value of
<em class="replaceable">
<code>
kdf_name
</code>
</em>
for encryption with
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
and
decryption with
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
. When you
specify
<em class="replaceable">
<code>
kdf_name
</code>
</em>
, you must
specify
<em class="replaceable">
<code>
init_vector
</code>
</em>
, using
either a valid initialization vector, or a null string
if the encryption mode does not require an
initialization vector.
</p>
<p>
The following values are supported:
</p>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<code class="literal">
hkdf
</code>
</span>
</dt>
<dd>
<p>
HKDF, which is available from OpenSSL 1.1.0. HKDF
extracts a pseudorandom key from the keying
material then expands it into additional keys.
With HKDF, you can specify an optional salt
(
<em class="replaceable">
<code>
salt
</code>
</em>
) and
context-specific information such as application
details (
<em class="replaceable">
<code>
info
</code>
</em>
) to
include in the keying material.
</p>
</dd>
<dt>
<span class="term">
<code class="literal">
pbkdf2_hmac
</code>
</span>
</dt>
<dd>
<p>
PBKDF2, which is available from OpenSSL 1.0.2.
PBKDF2 applies a pseudorandom function to the
keying material, and repeats this process a large
number of times to produce the key. With PBKDF2,
you can specify an optional salt
(
<em class="replaceable">
<code>
salt
</code>
</em>
) to include in
the keying material, and set the number of
iterations used to produce the key
(
<em class="replaceable">
<code>
iterations
</code>
</em>
).
</p>
</dd>
</dl>
</div>
<p>
In this example, HKDF is specified as the key derivation
function, and a salt and context information are
provided. The argument for the initialization vector is
included but is the empty string:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa2697150"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">AES_ENCRYPT</span><span class="token punctuation">(</span><span class="token string">'mytext'</span><span class="token punctuation">,</span><span class="token string">'mykeystring'</span><span class="token punctuation">,</span> <span class="token string">''</span><span class="token punctuation">,</span> <span class="token string">'hkdf'</span><span class="token punctuation">,</span> <span class="token string">'salt'</span><span class="token punctuation">,</span> <span class="token string">'info'</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
In this example, PBKDF2 is specified as the key
derivation function, a salt is provided, and the number
of iterations is doubled from the recommended minimum:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa13169593"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">AES_ENCRYPT</span><span class="token punctuation">(</span><span class="token string">'mytext'</span><span class="token punctuation">,</span><span class="token string">'mykeystring'</span><span class="token punctuation">,</span> <span class="token string">''</span><span class="token punctuation">,</span> <span class="token string">'pbkdf2_hmac'</span><span class="token punctuation">,</span><span class="token string">'salt'</span><span class="token punctuation">,</span> <span class="token string">'2000'</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
</dd>
<dt>
<span class="term">
<em class="replaceable">
<code>
salt
</code>
</em>
</span>
</dt>
<dd>
<p>
A salt to be passed to the key derivation function
(KDF). Optional. Both HKDF and PBKDF2 can use salts, and
their use is recommended to help prevent attacks based
on dictionaries of common passwords or rainbow tables.
</p>
<p>
A salt consists of random data, which for security must
be different for each encryption operation. A random
string of bytes to use for the salt can be produced by
calling
<a class="link" href="encryption-functions.html#function_random-bytes">
<code class="literal">
RANDOM_BYTES()
</code>
</a>
.
This example produces a 64-bit salt:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa69780846"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token variable">@salt</span> <span class="token operator">=</span> <span class="token function">RANDOM_BYTES</span><span class="token punctuation">(</span><span class="token number">8</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For the same instance of data, use the same value of
<em class="replaceable">
<code>
salt
</code>
</em>
for encryption with
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
and
decryption with
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
. The salt
can safely be stored along with the encrypted data.
</p>
</dd>
<dt>
<span class="term">
<em class="replaceable">
<code>
info
</code>
</em>
</span>
</dt>
<dd>
<p>
Context-specific information for HKDF to include in the
keying material, such as information about the
application. Optional; available when you specify
<code class="literal">
hkdf
</code>
as the KDF name. HKDF adds this
information to the keying material specified in
<em class="replaceable">
<code>
key_str
</code>
</em>
and the salt
specified in
<em class="replaceable">
<code>
salt
</code>
</em>
to produce
the key.
</p>
<p>
For the same instance of data, use the same value of
<em class="replaceable">
<code>
info
</code>
</em>
for encryption with
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
and
decryption with
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
.
</p>
</dd>
<dt>
<span class="term">
<em class="replaceable">
<code>
iterations
</code>
</em>
</span>
</dt>
<dd>
<p>
The iteration count for PBKDF2 to use when producing the
key. Optional; available when you specify
<code class="literal">
pbkdf2_hmac
</code>
as the KDF name. A higher
count gives greater resistance to brute-force attacks
because it has a greater computational cost for the
attacker, but the same is necessarily true for the key
derivation process. The default if you do not specify
this argument is 1000, which is the minimum recommended
by the OpenSSL standard.
</p>
<p>
For the same instance of data, use the same value of
<em class="replaceable">
<code>
iterations
</code>
</em>
for encryption
with
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
and
decryption with
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
.
</p>
</dd>
</dl>
</div>
<p>
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa96736067"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> block_encryption_mode <span class="token operator">=</span> <span class="token string">'aes-256-cbc'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@key_str</span> <span class="token operator">=</span> <span class="token function">SHA2</span><span class="token punctuation">(</span><span class="token string">'My secret passphrase'</span><span class="token punctuation">,</span><span class="token number">512</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@init_vector</span> <span class="token operator">=</span> <span class="token function">RANDOM_BYTES</span><span class="token punctuation">(</span><span class="token number">16</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@crypt_str</span> <span class="token operator">=</span> <span class="token function">AES_ENCRYPT</span><span class="token punctuation">(</span><span class="token string">'text'</span><span class="token punctuation">,</span><span class="token variable">@key_str</span><span class="token punctuation">,</span><span class="token variable">@init_vector</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">CAST</span><span class="token punctuation">(</span><span class="token function">AES_DECRYPT</span><span class="token punctuation">(</span><span class="token variable">@crypt_str</span><span class="token punctuation">,</span><span class="token variable">@key_str</span><span class="token punctuation">,</span><span class="token variable">@init_vector</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> <span class="token datatype">CHAR</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> CAST(AES_DECRYPT(@crypt_str,@key_str,@init_vector) AS CHAR) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> text <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_compress">
</a>
<p>
<a class="link" href="encryption-functions.html#function_compress">
<code class="literal">
COMPRESS(
<em class="replaceable">
<code>
string_to_compress
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045199375152">
</a>
<p>
Compresses a string and returns the result as a binary string.
This function requires MySQL to have been compiled with a
compression library such as
<code class="literal">
zlib
</code>
.
Otherwise, the return value is always
<code class="literal">
NULL
</code>
.
The return value is also
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
string_to_compress
</code>
</em>
is
<code class="literal">
NULL
</code>
. The compressed string can be
uncompressed with
<a class="link" href="encryption-functions.html#function_uncompress">
<code class="literal">
UNCOMPRESS()
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47687868"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">LENGTH</span><span class="token punctuation">(</span><span class="token function">COMPRESS</span><span class="token punctuation">(</span><span class="token function">REPEAT</span><span class="token punctuation">(</span><span class="token string">'a'</span><span class="token punctuation">,</span><span class="token number">1000</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">21</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">LENGTH</span><span class="token punctuation">(</span><span class="token function">COMPRESS</span><span class="token punctuation">(</span><span class="token string">''</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">LENGTH</span><span class="token punctuation">(</span><span class="token function">COMPRESS</span><span class="token punctuation">(</span><span class="token string">'a'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">13</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">LENGTH</span><span class="token punctuation">(</span><span class="token function">COMPRESS</span><span class="token punctuation">(</span><span class="token function">REPEAT</span><span class="token punctuation">(</span><span class="token string">'a'</span><span class="token punctuation">,</span><span class="token number">16</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">15</span></code></pre>
</div>
<p>
The compressed string contents are stored the following way:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Empty strings are stored as empty strings.
</p>
</li>
<li class="listitem">
<p>
Nonempty strings are stored as a 4-byte length of the
uncompressed string (low byte first), followed by the
compressed string. If the string ends with space, an extra
<code class="literal">
.
</code>
character is added to avoid problems
with endspace trimming should the result be stored in a
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
or
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
column. (However,
use of nonbinary string data types such as
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
or
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
to store compressed
strings is not recommended anyway because character set
conversion may occur. Use a
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
VARBINARY
</code>
</a>
or
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
binary string column
instead.)
</p>
</li>
</ul>
</div>
<p>
If
<a class="link" href="encryption-functions.html#function_compress">
<code class="literal">
COMPRESS()
</code>
</a>
is invoked from
within the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client, binary strings
display using hexadecimal notation, depending on the value of
the
<a class="link" href="mysql-command-options.html#option_mysql_binary-as-hex">
<code class="option">
--binary-as-hex
</code>
</a>
. For more
information about that option, see
<a class="xref" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
Section 6.5.1, “mysql — The MySQL Command-Line Client”
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_md5">
</a>
<p>
<a class="link" href="encryption-functions.html#function_md5">
<code class="literal">
MD5(
<em class="replaceable">
<code>
str
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045199342144">
</a>
<p>
Calculates an MD5 128-bit checksum for the string. The value
is returned as a string of 32 hexadecimal digits, or
<code class="literal">
NULL
</code>
if the argument was
<code class="literal">
NULL
</code>
. The return value can, for example, be
used as a hash key. See the notes at the beginning of this
section about storing hash values efficiently.
</p>
<p>
The return value is a string in the connection character set.
</p>
<p>
If FIPS mode is enabled,
<code class="function">
MD5()
</code>
returns
<code class="literal">
NULL
</code>
. See
<a class="xref" href="fips-mode.html" title="8.8 FIPS Support">
Section 8.8, “FIPS Support”
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa77658121"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">MD5</span><span class="token punctuation">(</span><span class="token string">'testing'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'ae2b1fca515949e5d54fb22b8ed95575'</span></code></pre>
</div>
<p>
This is the
<span class="quote">
“
<span class="quote">
RSA Data Security, Inc. MD5 Message-Digest
Algorithm.
</span>
”
</span>
</p>
<p>
See the note regarding the MD5 algorithm at the beginning this
section.
</p>
</li>
<li class="listitem">
<a name="function_random-bytes">
</a>
<p>
<a class="link" href="encryption-functions.html#function_random-bytes">
<code class="literal">
RANDOM_BYTES(
<em class="replaceable">
<code>
len
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045199325552">
</a>
<p>
This function returns a binary string of
<em class="replaceable">
<code>
len
</code>
</em>
random bytes generated using
the random number generator of the SSL library. Permitted
values of
<em class="replaceable">
<code>
len
</code>
</em>
range from 1 to 1024.
For values outside that range, an error occurs. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
len
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<p>
<a class="link" href="encryption-functions.html#function_random-bytes">
<code class="literal">
RANDOM_BYTES()
</code>
</a>
can be used to
provide the initialization vector for the
<a class="link" href="encryption-functions.html#function_aes-decrypt">
<code class="literal">
AES_DECRYPT()
</code>
</a>
and
<a class="link" href="encryption-functions.html#function_aes-encrypt">
<code class="literal">
AES_ENCRYPT()
</code>
</a>
functions. For
use in that context,
<em class="replaceable">
<code>
len
</code>
</em>
must be at
least 16. Larger values are permitted, but bytes in excess of
16 are ignored.
</p>
<p>
<a class="link" href="encryption-functions.html#function_random-bytes">
<code class="literal">
RANDOM_BYTES()
</code>
</a>
generates a
random value, which makes its result nondeterministic.
Consequently, statements that use this function are unsafe for
statement-based replication.
</p>
<p>
If
<a class="link" href="encryption-functions.html#function_random-bytes">
<code class="literal">
RANDOM_BYTES()
</code>
</a>
is invoked
from within the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client, binary
strings display using hexadecimal notation, depending on the
value of the
<a class="link" href="mysql-command-options.html#option_mysql_binary-as-hex">
<code class="option">
--binary-as-hex
</code>
</a>
.
For more information about that option, see
<a class="xref" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
Section 6.5.1, “mysql — The MySQL Command-Line Client”
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_sha1">
</a>
<p>
<a class="link" href="encryption-functions.html#function_sha1">
<code class="literal">
SHA1(
<em class="replaceable">
<code>
str
</code>
</em>
)
</code>
</a>
,
<a class="link" href="encryption-functions.html#function_sha1">
<code class="literal">
SHA(
<em class="replaceable">
<code>
str
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045199301952">
</a>
<a class="indexterm" name="idm46045199300880">
</a>
<p>
Calculates an SHA-1 160-bit checksum for the string, as
described in RFC 3174 (Secure Hash Algorithm). The value is
returned as a string of 40 hexadecimal digits, or
<code class="literal">
NULL
</code>
if the argument is
<code class="literal">
NULL
</code>
. One of the possible uses for this
function is as a hash key. See the notes at the beginning of
this section about storing hash values efficiently.
<a class="link" href="encryption-functions.html#function_sha1">
<code class="literal">
SHA()
</code>
</a>
is
synonymous with
<a class="link" href="encryption-functions.html#function_sha1">
<code class="literal">
SHA1()
</code>
</a>
.
</p>
<p>
The return value is a string in the connection character set.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa93101863"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SHA1</span><span class="token punctuation">(</span><span class="token string">'abc'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'a9993e364706816aba3e25717850c26c9cd0d89d'</span></code></pre>
</div>
<p>
<a class="link" href="encryption-functions.html#function_sha1">
<code class="literal">
SHA1()
</code>
</a>
can be considered a
cryptographically more secure equivalent of
<a class="link" href="encryption-functions.html#function_md5">
<code class="literal">
MD5()
</code>
</a>
. However, see the note
regarding the MD5 and SHA-1 algorithms at the beginning this
section.
</p>
</li>
<li class="listitem">
<a name="function_sha2">
</a>
<p>
<a class="link" href="encryption-functions.html#function_sha2">
<code class="literal">
SHA2(
<em class="replaceable">
<code>
str
</code>
</em>
,
<em class="replaceable">
<code>
hash_length
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045199282464">
</a>
<p>
Calculates the SHA-2 family of hash functions (SHA-224,
SHA-256, SHA-384, and SHA-512). The first argument is the
plaintext string to be hashed. The second argument indicates
the desired bit length of the result, which must have a value
of 224, 256, 384, 512, or 0 (which is equivalent to 256). If
either argument is
<code class="literal">
NULL
</code>
or the hash length
is not one of the permitted values, the return value is
<code class="literal">
NULL
</code>
. Otherwise, the function result is a
hash value containing the desired number of bits. See the
notes at the beginning of this section about storing hash
values efficiently.
</p>
<p>
The return value is a string in the connection character set.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa15256203"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">SHA2</span><span class="token punctuation">(</span><span class="token string">'abc'</span><span class="token punctuation">,</span> <span class="token number">224</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'23097d223405d8228642a477bda255b32aadbce4bda0b3f7e36c9da7'</span></code></pre>
</div>
<p>
This function works only if MySQL has been configured with SSL
support. See
<a class="xref" href="encrypted-connections.html" title="8.3 Using Encrypted Connections">
Section 8.3, “Using Encrypted Connections”
</a>
.
</p>
<p>
<a class="link" href="encryption-functions.html#function_sha2">
<code class="literal">
SHA2()
</code>
</a>
can be considered
cryptographically more secure than
<a class="link" href="encryption-functions.html#function_md5">
<code class="literal">
MD5()
</code>
</a>
or
<a class="link" href="encryption-functions.html#function_sha1">
<code class="literal">
SHA1()
</code>
</a>
.
</p>
</li>
<li class="listitem">
<a name="function_statement-digest">
</a>
<p>
<a class="link" href="encryption-functions.html#function_statement-digest">
<code class="literal">
STATEMENT_DIGEST(
<em class="replaceable">
<code>
statement
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045199264224">
</a>
<p>
Given an SQL statement as a string, returns the statement
digest hash value as a string in the connection character set,
or
<code class="literal">
NULL
</code>
if the argument is
<code class="literal">
NULL
</code>
. The related
<a class="link" href="encryption-functions.html#function_statement-digest-text">
<code class="literal">
STATEMENT_DIGEST_TEXT()
</code>
</a>
function returns the normalized statement digest. For
information about statement digesting, see
<a class="xref" href="performance-schema-statement-digests.html" title="29.10 Performance Schema Statement Digests and Sampling">
Section 29.10, “Performance Schema Statement Digests and Sampling”
</a>
.
</p>
<p>
Both functions use the MySQL parser to parse the statement. If
parsing fails, an error occurs. The error message includes the
parse error only if the statement is provided as a literal
string.
</p>
<p>
The
<a class="link" href="server-system-variables.html#sysvar_max_digest_length">
<code class="literal">
max_digest_length
</code>
</a>
system
variable determines the maximum number of bytes available to
these functions for computing normalized statement digests.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa92891910"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@stmt</span> <span class="token operator">=</span> <span class="token string">'SELECT * FROM mytable WHERE cola = 10 AND colb = 20'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STATEMENT_DIGEST</span><span class="token punctuation">(</span><span class="token variable">@stmt</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> STATEMENT_DIGEST(@stmt) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 3bb95eeade896657c4526e74ff2a2862039d0a0fe8a9e7155b5fe492cbd78387 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">STATEMENT_DIGEST_TEXT</span><span class="token punctuation">(</span><span class="token variable">@stmt</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> STATEMENT_DIGEST_TEXT(@stmt) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> SELECT * FROM `mytable` WHERE `cola` = ? AND `colb` = ? <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_statement-digest-text">
</a>
<p>
<a class="link" href="encryption-functions.html#function_statement-digest-text">
<code class="literal">
STATEMENT_DIGEST_TEXT(
<em class="replaceable">
<code>
statement
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045199245984">
</a>
<p>
Given an SQL statement as a string, returns the normalized
statement digest as a string in the connection character set,
or
<code class="literal">
NULL
</code>
if the argument is
<code class="literal">
NULL
</code>
. For additional discussion and
examples, see the description of the related
<a class="link" href="encryption-functions.html#function_statement-digest">
<code class="literal">
STATEMENT_DIGEST()
</code>
</a>
function.
</p>
</li>
<li class="listitem">
<a name="function_uncompress">
</a>
<p>
<a class="link" href="encryption-functions.html#function_uncompress">
<code class="literal">
UNCOMPRESS(
<em class="replaceable">
<code>
string_to_uncompress
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045199236288">
</a>
<p>
Uncompresses a string compressed by the
<a class="link" href="encryption-functions.html#function_compress">
<code class="literal">
COMPRESS()
</code>
</a>
function. If the
argument is not a compressed value, the result is
<code class="literal">
NULL
</code>
; if
<em class="replaceable">
<code>
string_to_uncompress
</code>
</em>
is
<code class="literal">
NULL
</code>
, the result is also
<code class="literal">
NULL
</code>
. This function requires MySQL to have
been compiled with a compression library such as
<code class="literal">
zlib
</code>
. Otherwise, the return value is always
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa59641139"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">UNCOMPRESS</span><span class="token punctuation">(</span><span class="token function">COMPRESS</span><span class="token punctuation">(</span><span class="token string">'any string'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'any string'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">UNCOMPRESS</span><span class="token punctuation">(</span><span class="token string">'any string'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token boolean">NULL</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_uncompressed-length">
</a>
<p>
<a class="link" href="encryption-functions.html#function_uncompressed-length">
<code class="literal">
UNCOMPRESSED_LENGTH(
<em class="replaceable">
<code>
compressed_string
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045199219760">
</a>
<p>
Returns the length that the compressed string had before being
compressed. Returns
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
compressed_string
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34864714"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">UNCOMPRESSED_LENGTH</span><span class="token punctuation">(</span><span class="token function">COMPRESS</span><span class="token punctuation">(</span><span class="token function">REPEAT</span><span class="token punctuation">(</span><span class="token string">'a'</span><span class="token punctuation">,</span><span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">30</span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_validate-password-strength">
</a>
<p>
<a class="link" href="encryption-functions.html#function_validate-password-strength">
<code class="literal">
VALIDATE_PASSWORD_STRENGTH(
<em class="replaceable">
<code>
str
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045199207680">
</a>
<p>
Given an argument representing a plaintext password, this
function returns an integer to indicate how strong the
password is, or
<code class="literal">
NULL
</code>
if the argument is
<code class="literal">
NULL
</code>
. The return value ranges from 0 (weak)
to 100 (strong).
</p>
<p>
Password assessment by
<a class="link" href="encryption-functions.html#function_validate-password-strength">
<code class="literal">
VALIDATE_PASSWORD_STRENGTH()
</code>
</a>
is
done by the
<code class="literal">
validate_password
</code>
component. If
that component is not installed, the function always returns
0. For information about installing
<code class="literal">
validate_password
</code>
, see
<a class="xref" href="validate-password.html" title="8.4.3 The Password Validation Component">
Section 8.4.3, “The Password Validation Component”
</a>
. To examine or configure
the parameters that affect password testing, check or set the
system variables implemented by
<code class="literal">
validate_password
</code>
. See
<a class="xref" href="validate-password-options-variables.html" title="8.4.3.2 Password Validation Options and Variables">
Section 8.4.3.2, “Password Validation Options and Variables”
</a>
.
</p>
<p>
The password is subjected to increasingly strict tests and the
return value reflects which tests were satisfied, as shown in
the following table. In addition, if the
<a class="link" href="validate-password-options-variables.html#sysvar_validate_password.check_user_name">
<code class="literal">
validate_password.check_user_name
</code>
</a>
system variable is enabled and the password matches the user
name,
<a class="link" href="encryption-functions.html#function_validate-password-strength">
<code class="literal">
VALIDATE_PASSWORD_STRENGTH()
</code>
</a>
returns 0 regardless of how other
<code class="literal">
validate_password
</code>
system variables are set.
</p>
<div class="informaltable">
<table summary="Password tests of the VALIDATE_PASSWORD_STRENGTH() function and the values returned by each password test.">
<colgroup>
<col style="width: 60%"/>
<col style="width: 20%"/>
</colgroup>
<thead>
<tr>
<th>
Password Test
</th>
<th>
Return Value
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
Length < 4
</td>
<td>
0
</td>
</tr>
<tr>
<td>
Length ≥ 4 and <
<a class="link" href="validate-password-options-variables.html#sysvar_validate_password.length">
<code class="literal">
validate_password.length
</code>
</a>
</td>
<td>
25
</td>
</tr>
<tr>
<td>
Satisfies policy 1 (
<code class="literal">
LOW
</code>
)
</td>
<td>
50
</td>
</tr>
<tr>
<td>
Satisfies policy 2 (
<code class="literal">
MEDIUM
</code>
)
</td>
<td>
75
</td>
</tr>
<tr>
<td>
Satisfies policy 3 (
<code class="literal">
STRONG
</code>
)
</td>
<td>
100
</td>
</tr>
</tbody>
</table>
</div>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/installation-layouts.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="installation-layouts">
</a>
2.1.5 Installation Layouts
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045332671856">
</a>
<a class="indexterm" name="idm46045332670784">
</a>
<a class="indexterm" name="idm46045332669712">
</a>
<a class="indexterm" name="idm46045332668224">
</a>
<p>
The installation layout differs for different installation types
(for example, native packages, binary tarballs, and source
tarballs), which can lead to confusion when managing different
systems or using different installation sources. The individual
layouts are given in the corresponding installation type or
platform chapter, as described following. Note that the layout of
installations from vendors other than Oracle may differ from these
layouts.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="ulink" href="/doc/refman/8.0/en/windows-installation-layout.html" target="_top">
MySQL Installation Layout on Microsoft Windows
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="source-installation-layout.html" title="2.8.3 MySQL Layout for Source Installation">
Section 2.8.3, “MySQL Layout for Source Installation”
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="binary-installation.html#binary-installation-layout" title="Table 2.3 MySQL Installation Layout for Generic Unix/Linux Binary Package">
Table 2.3, “MySQL Installation Layout for Generic Unix/Linux Binary Package”
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="linux-installation-rpm.html#mysql-installation-layout-linuxrpm" title="Table 2.11 MySQL Installation Layout for Linux RPM Packages from the MySQL Developer Zone">
Table 2.11, “MySQL Installation Layout for Linux RPM Packages from the MySQL Developer Zone”
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="macos-installation-pkg.html#mysql-installation-layout-macos" title="Table 2.6 MySQL Installation Layout on macOS">
Table 2.6, “MySQL Installation Layout on macOS”
</a>
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-shell-tutorial-javascript-documents-collections.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysql-shell-tutorial-javascript-documents-collections">
</a>
22.3.3 Documents and Collections
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript-collections-operations.html">
22.3.3.1 Create, List, and Drop Collections
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript-collections-add.html">
22.3.3.2 Working with Collections
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript-documents-find.html">
22.3.3.3 Find Documents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript-documents-modify.html">
22.3.3.4 Modify Documents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript-documents-remove.html">
22.3.3.5 Remove Documents
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="mysql-shell-tutorial-javascript-indexes-create.html">
22.3.3.6 Create and Drop Indexes
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045128015632">
</a>
<p>
When you are using MySQL as a Document Store, collections are
containers within a schema that you can create, list, and drop.
Collections contain JSON documents that you can add, find, update,
and remove.
</p>
<p>
The examples in this section use the
<code class="literal">
countryinfo
</code>
collection in the
<code class="literal">
world_x
</code>
schema. For instructions on setting up
the
<code class="literal">
world_x
</code>
schema, see
<a class="xref" href="mysql-shell-tutorial-javascript-download.html" title="22.3.2 Download and Import world_x Database">
Section 22.3.2, “Download and Import world_x Database”
</a>
.
</p>
<h4>
<a name="mysql-shell-tutorial-javascript-documents">
</a>
Documents
</h4>
<p>
In MySQL, documents are represented as JSON objects. Internally,
they are stored in an efficient binary format that enables fast
lookups and updates.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Simple document format for JavaScript:
</p>
<pre class="screen">{field1: "value", field2 : 10, "field 3": null}
</pre>
</li>
</ul>
</div>
<p>
An array of documents consists of a set of documents separated by
commas and enclosed within
<code class="literal">
[
</code>
and
<code class="literal">
]
</code>
characters.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Simple array of documents for JavaScript:
</p>
<pre class="screen">[{"Name": "Aruba", "Code:": "ABW"}, {"Name": "Angola", "Code:": "AGO"}]
</pre>
</li>
</ul>
</div>
<p>
MySQL supports the following JavaScript value types in JSON
documents:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
numbers (integer and floating point)
</p>
</li>
<li class="listitem">
<p>
strings
</p>
</li>
<li class="listitem">
<p>
boolean (False and True)
</p>
</li>
<li class="listitem">
<p>
null
</p>
</li>
<li class="listitem">
<p>
arrays of more JSON values
</p>
</li>
<li class="listitem">
<p>
nested (or embedded) objects of more JSON values
</p>
</li>
</ul>
</div>
<h4>
<a name="mysql-shell-tutorial-javascript-collections">
</a>
Collections
</h4>
<p>
Collections are containers for documents that share a purpose and
possibly share one or more indexes. Each collection has a unique
name and exists within a single schema.
</p>
<p>
The term schema is equivalent to a database, which means a group
of database objects as opposed to a relational schema, used to
enforce structure and constraints over data. A schema does not
enforce conformity on the documents in a collection.
</p>
<p>
In this quick-start guide:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Basic objects include:
</p>
<div class="informaltable">
<table summary="Objects to use interactively in MySQL Shell">
<colgroup>
<col style="width: 40%"/>
<col style="width: 60%"/>
</colgroup>
<thead>
<tr>
<th>
Object form
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
db
</code>
</td>
<td>
<code class="literal">
db
</code>
is a global variable assigned to the current
active schema. When you want to run operations against
the schema, for example to retrieve a collection, you
use methods available for the
<code class="literal">
db
</code>
variable.
</td>
</tr>
<tr>
<td>
<code class="literal">
db.getCollections()
</code>
</td>
<td>
<a class="link" href="mysql-shell-tutorial-javascript-collections-operations.html#mysql-shell-tutorial-javascript-collections-get" title="List Collections">
db.getCollections()
</a>
returns a list of collections in the schema. Use the
list to get references to collection objects, iterate
over them, and so on.
</td>
</tr>
</tbody>
</table>
</div>
</li>
<li class="listitem">
<p>
Basic operations scoped by collections include:
</p>
<div class="informaltable">
<table summary="CRUD operations available in X DevAPI">
<colgroup>
<col style="width: 40%"/>
<col style="width: 60%"/>
</colgroup>
<thead>
<tr>
<th>
Operation form
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
db.
<em class="replaceable">
<code>
name
</code>
</em>
.add()
</code>
</td>
<td>
The
<a class="link" href="mysql-shell-tutorial-javascript-collections-add.html" title="22.3.3.2 Working with Collections">
add()
</a>
method inserts one document or a list of documents into
the named collection.
</td>
</tr>
<tr>
<td>
<code class="literal">
db.
<em class="replaceable">
<code>
name
</code>
</em>
.find()
</code>
</td>
<td>
The
<a class="link" href="mysql-shell-tutorial-javascript-documents-find.html" title="22.3.3.3 Find Documents">
find()
</a>
method returns some or all documents in the named
collection.
</td>
</tr>
<tr>
<td>
<code class="literal">
db.
<em class="replaceable">
<code>
name
</code>
</em>
.modify()
</code>
</td>
<td>
The
<a class="link" href="mysql-shell-tutorial-javascript-documents-modify.html" title="22.3.3.4 Modify Documents">
modify()
</a>
method updates documents in the named collection.
</td>
</tr>
<tr>
<td>
<code class="literal">
db.
<em class="replaceable">
<code>
name
</code>
</em>
.remove()
</code>
</td>
<td>
The
<a class="link" href="mysql-shell-tutorial-javascript-documents-remove.html" title="22.3.3.5 Remove Documents">
remove()
</a>
method deletes one document or a list of documents from
the named collection.
</td>
</tr>
</tbody>
</table>
</div>
</li>
</ul>
</div>
<h4>
<a name="idm46045127957440">
</a>
Related Information
</h4>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
See
<a class="ulink" href="/doc/x-devapi-userguide/en/devapi-users-working-with-collections.html" target="_top">
Working with Collections
</a>
for a general overview.
</p>
</li>
<li class="listitem">
<p>
<a class="ulink" href="/doc/x-devapi-userguide/en/mysql-x-crud-ebnf-definitions.html" target="_top">
CRUD EBNF Definitions
</a>
provides a
complete list of operations.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/thread-pool.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="thread-pool">
</a>
7.6.3 MySQL Enterprise Thread Pool
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="thread-pool-elements.html">
7.6.3.1 Thread Pool Elements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="thread-pool-installation.html">
7.6.3.2 Thread Pool Installation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="thread-pool-operation.html">
7.6.3.3 Thread Pool Operation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="thread-pool-tuning.html">
7.6.3.4 Thread Pool Tuning
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045256870816">
</a>
<a class="indexterm" name="idm46045256869760">
</a>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
MySQL Enterprise Thread Pool is an extension included in MySQL Enterprise Edition, a commercial product.
To learn more about commercial products,
<a class="ulink" href="https://www.mysql.com/products/" target="_blank">
https://www.mysql.com/products/
</a>
.
</p>
</div>
<p>
MySQL Enterprise Edition includes MySQL Enterprise Thread Pool, implemented using a server plugin. The
default thread-handling model in MySQL Server executes statements
using one thread per client connection. As more clients connect to
the server and execute statements, overall performance degrades.
The thread pool plugin provides an alternative thread-handling
model designed to reduce overhead and improve performance. The
plugin implements a thread pool that increases server performance
by efficiently managing statement execution threads for large
numbers of client connections.
</p>
<p>
The thread pool addresses several problems of the model that uses
one thread per connection:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Too many thread stacks make CPU caches almost useless in
highly parallel execution workloads. The thread pool promotes
thread stack reuse to minimize the CPU cache footprint.
</p>
</li>
<li class="listitem">
<p>
With too many threads executing in parallel, context switching
overhead is high. This also presents a challenge to the
operating system scheduler. The thread pool controls the
number of active threads to keep the parallelism within the
MySQL server at a level that it can handle and that is
appropriate for the server host on which MySQL is executing.
</p>
</li>
<li class="listitem">
<p>
Too many transactions executing in parallel increases resource
contention. In
<a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
<code class="literal">
InnoDB
</code>
</a>
, this
increases the time spent holding central mutexes. The thread
pool controls when transactions start to ensure that not too
many execute in parallel.
</p>
</li>
</ul>
</div>
<h4>
<a name="idm46045256860304">
</a>
Additional Resources
</h4>
<p>
<a class="xref" href="faqs-thread-pool.html" title="A.15 MySQL 8.4 FAQ: MySQL Enterprise Thread Pool">
Section A.15, “MySQL 8.4 FAQ: MySQL Enterprise Thread Pool”
</a>
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-shell-tutorial-javascript-documents-find.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-shell-tutorial-javascript-documents-find">
</a>
22.3.3.3 Find Documents
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127886560">
</a>
<p>
You can use the
<code class="literal">
find()
</code>
method to query for
and return documents from a collection in a schema. MySQL Shell
provides additional methods to use with the
<code class="literal">
find()
</code>
method to filter and sort the returned
documents.
</p>
<p>
MySQL provides the following operators to specify search
conditions:
<code class="literal">
OR
</code>
(
<code class="literal">
||
</code>
),
<code class="literal">
AND
</code>
(
<code class="literal">
&&
</code>
),
<code class="literal">
XOR
</code>
,
<code class="literal">
IS
</code>
,
<code class="literal">
NOT
</code>
,
<code class="literal">
BETWEEN
</code>
,
<code class="literal">
IN
</code>
,
<code class="literal">
LIKE
</code>
,
<code class="literal">
!=
</code>
,
<code class="literal">
<>
</code>
,
<code class="literal">
>
</code>
,
<code class="literal">
>=
</code>
,
<code class="literal">
<
</code>
,
<code class="literal">
<=
</code>
,
<code class="literal">
&
</code>
,
<code class="literal">
|
</code>
,
<code class="literal">
<<
</code>
,
<code class="literal">
>>
</code>
,
<code class="literal">
+
</code>
,
<code class="literal">
-
</code>
,
<code class="literal">
*
</code>
,
<code class="literal">
/
</code>
,
<code class="literal">
~
</code>
, and
<code class="literal">
%
</code>
.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="mysql-shell-tutorial-javascript-documents-find-all">
</a>
Find All Documents in a Collection
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127863488">
</a>
<p>
To return all documents in a collection, use the
<code class="literal">
find()
</code>
method without specifying search
conditions. For example, the following operation returns all
documents in the
<code class="literal">
countryinfo
</code>
collection.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa36442313"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token inlinejson"><span class="token punctuation">[</span>
<span class="token punctuation">{</span>
<span class="token property">"GNP"</span><span class="token operator">:</span> <span class="token number">828</span><span class="token punctuation">,</span>
<span class="token property">"Code:"</span><span class="token operator">:</span> <span class="token string">"ABW"</span><span class="token punctuation">,</span>
<span class="token property">"Name"</span><span class="token operator">:</span> <span class="token string">"Aruba"</span><span class="token punctuation">,</span>
<span class="token property">"IndepYear"</span><span class="token operator">:</span> <span class="token null">null</span><span class="token punctuation">,</span>
<span class="token property">"geography"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Continent"</span><span class="token operator">:</span> <span class="token string">"North America"</span><span class="token punctuation">,</span>
<span class="token property">"Region"</span><span class="token operator">:</span> <span class="token string">"Caribbean"</span><span class="token punctuation">,</span>
<span class="token property">"SurfaceArea"</span><span class="token operator">:</span> <span class="token number">193</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"government"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"GovernmentForm"</span><span class="token operator">:</span> <span class="token string">"Nonmetropolitan Territory of The Netherlands"</span><span class="token punctuation">,</span>
<span class="token property">"HeadOfState"</span><span class="token operator">:</span> <span class="token string">"Beatrix"</span>
<span class="token punctuation">}</span>
<span class="token property">"demographics"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"LifeExpectancy"</span><span class="token operator">:</span> <span class="token number">78.4000015258789</span><span class="token punctuation">,</span>
<span class="token property">"Population"</span><span class="token operator">:</span> <span class="token number">103000</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
...
<span class="token punctuation">}</span>
<span class="token punctuation">]</span></span>
<span class="token output">240 documents in set (0.00 sec)</span></code></pre>
</div>
<p>
The method produces results that contain operational
information in addition to all documents in the collection.
</p>
<p>
An empty set (no matching documents) returns the following
information:
</p>
<pre class="screen">Empty set (0.00 sec)
</pre>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="mysql-shell-tutorial-javascript-documents-find-filter-searches">
</a>
Filter Searches
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127854640">
</a>
<p>
You can include search conditions with the
<code class="literal">
find()
</code>
method. The syntax for expressions
that form a search condition is the same as that of
traditional MySQL
<a class="xref" href="functions.html" title="Chapter 14 Functions and Operators">
Chapter 14,
<i>
Functions and Operators
</i>
</a>
. You must
enclose all expressions in quotes. For the sake of brevity,
some of the examples do not display output.
</p>
<p>
A simple search condition could consist of the
<code class="literal">
Name
</code>
field and a value we know is in a
document. The following example returns a single document:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa49397270"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token string">"Name = 'Australia'"</span><span class="token punctuation">)</span>
<span class="token inlinejson"><span class="token punctuation">[</span>
<span class="token punctuation">{</span>
<span class="token property">"GNP"</span><span class="token operator">:</span> <span class="token number">351182</span><span class="token punctuation">,</span>
<span class="token property">"Code:"</span><span class="token operator">:</span> <span class="token string">"AUS"</span><span class="token punctuation">,</span>
<span class="token property">"Name"</span><span class="token operator">:</span> <span class="token string">"Australia"</span><span class="token punctuation">,</span>
<span class="token property">"IndepYear"</span><span class="token operator">:</span> <span class="token number">1901</span><span class="token punctuation">,</span>
<span class="token property">"geography"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Continent"</span><span class="token operator">:</span> <span class="token string">"Oceania"</span><span class="token punctuation">,</span>
<span class="token property">"Region"</span><span class="token operator">:</span> <span class="token string">"Australia and New Zealand"</span><span class="token punctuation">,</span>
<span class="token property">"SurfaceArea"</span><span class="token operator">:</span> <span class="token number">7741220</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"government"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"GovernmentForm"</span><span class="token operator">:</span> <span class="token string">"Constitutional Monarchy, Federation"</span><span class="token punctuation">,</span>
<span class="token property">"HeadOfState"</span><span class="token operator">:</span> <span class="token string">"Elisabeth II"</span>
<span class="token punctuation">}</span>
<span class="token property">"demographics"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"LifeExpectancy"</span><span class="token operator">:</span> <span class="token number">79.80000305175781</span><span class="token punctuation">,</span>
<span class="token property">"Population"</span><span class="token operator">:</span> <span class="token number">18886000</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token punctuation">}</span>
<span class="token punctuation">]</span></span></code></pre>
</div>
<p>
The following example searches for all countries that have a
GNP higher than $500 billion. The
<code class="literal">
countryinfo
</code>
collection measures GNP in
units of million.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa29624110"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token string">"GNP > 500000"</span><span class="token punctuation">)</span>
<span class="token operator">...</span><span class="token punctuation">[</span><em>output removed</em><span class="token punctuation">]</span>
<span class="token output">10 documents in set (0.00 sec)</span></code></pre>
</div>
<p>
The Population field in the following query is embedded within
the demographics object. To access the embedded field, use a
period between demographics and Population to identify the
relationship. Document and field names are case-sensitive.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa5570606"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token string">"GNP > 500000 and demographics.Population < 100000000"</span><span class="token punctuation">)</span>
<span class="token operator">...</span><span class="token punctuation">[</span><em>output removed</em><span class="token punctuation">]</span>
<span class="token output">6 documents in set (0.00 sec)</span></code></pre>
</div>
<p>
Arithmetic operators in the following expression are used to
query for countries with a GNP per capita higher than $30000.
Search conditions can include arithmetic operators and most
MySQL functions.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Seven documents in the
<code class="literal">
countryinfo
</code>
collection have a population value of zero. Therefore
warning messages appear at the end of the output.
</p>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa82136603"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token string">"GNP*1000000/demographics.Population > 30000"</span><span class="token punctuation">)</span>
<span class="token operator">...</span><span class="token punctuation">[</span><em>output removed</em><span class="token punctuation">]</span>
<span class="token output">9 documents in set, 7 warnings (0.00 sec)</span>
Warning <span class="token punctuation">(</span>Code <span class="token number">1365</span><span class="token punctuation">)</span><span class="token punctuation">:</span> Division by <span class="token number">0</span>
Warning <span class="token punctuation">(</span>Code <span class="token number">1365</span><span class="token punctuation">)</span><span class="token punctuation">:</span> Division by <span class="token number">0</span>
Warning <span class="token punctuation">(</span>Code <span class="token number">1365</span><span class="token punctuation">)</span><span class="token punctuation">:</span> Division by <span class="token number">0</span>
Warning <span class="token punctuation">(</span>Code <span class="token number">1365</span><span class="token punctuation">)</span><span class="token punctuation">:</span> Division by <span class="token number">0</span>
Warning <span class="token punctuation">(</span>Code <span class="token number">1365</span><span class="token punctuation">)</span><span class="token punctuation">:</span> Division by <span class="token number">0</span>
Warning <span class="token punctuation">(</span>Code <span class="token number">1365</span><span class="token punctuation">)</span><span class="token punctuation">:</span> Division by <span class="token number">0</span>
Warning <span class="token punctuation">(</span>Code <span class="token number">1365</span><span class="token punctuation">)</span><span class="token punctuation">:</span> Division by <span class="token number">0</span></code></pre>
</div>
<p>
You can separate a value from the search condition by using
the
<code class="literal">
bind()
</code>
method. For example, instead of
specifying a hard-coded country name as the condition,
substitute a named placeholder consisting of a colon followed
by a name that begins with a letter, such as
<span class="emphasis">
<em>
country
</em>
</span>
. Then use the
<code class="literal">
bind(
<em class="replaceable">
<code>
placeholder
</code>
</em>
,
<em class="replaceable">
<code>
value
</code>
</em>
)
</code>
method as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa99167742"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token string">"Name = :country"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token string">"country"</span><span class="token punctuation">,</span> <span class="token string">"Italy"</span><span class="token punctuation">)</span>
<span class="token inlinejson"><span class="token punctuation">{</span>
<span class="token property">"GNP"</span><span class="token operator">:</span> <span class="token number">1161755</span><span class="token punctuation">,</span>
<span class="token property">"_id"</span><span class="token operator">:</span> <span class="token string">"00005de917d8000000000000006a"</span><span class="token punctuation">,</span>
<span class="token property">"Code"</span><span class="token operator">:</span> <span class="token string">"ITA"</span><span class="token punctuation">,</span>
<span class="token property">"Name"</span><span class="token operator">:</span> <span class="token string">"Italy"</span><span class="token punctuation">,</span>
<span class="token property">"Airports"</span><span class="token operator">:</span> <span class="token punctuation">[</span><span class="token punctuation">]</span><span class="token punctuation">,</span>
<span class="token property">"IndepYear"</span><span class="token operator">:</span> <span class="token number">1861</span><span class="token punctuation">,</span>
<span class="token property">"geography"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Region"</span><span class="token operator">:</span> <span class="token string">"Southern Europe"</span><span class="token punctuation">,</span>
<span class="token property">"Continent"</span><span class="token operator">:</span> <span class="token string">"Europe"</span><span class="token punctuation">,</span>
<span class="token property">"SurfaceArea"</span><span class="token operator">:</span> <span class="token number">301316</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"government"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"HeadOfState"</span><span class="token operator">:</span> <span class="token string">"Carlo Azeglio Ciampi"</span><span class="token punctuation">,</span>
<span class="token property">"GovernmentForm"</span><span class="token operator">:</span> <span class="token string">"Republic"</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"demographics"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Population"</span><span class="token operator">:</span> <span class="token number">57680000</span><span class="token punctuation">,</span>
<span class="token property">"LifeExpectancy"</span><span class="token operator">:</span> <span class="token number">79</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span></span>
<span class="token output">1 document in set (0.01 sec)</span></code></pre>
</div>
<div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Tip
</div>
<p>
Within a program, binding enables you to specify
placeholders in your expressions, which are filled in with
values before execution and can benefit from automatic
escaping, as appropriate.
</p>
<p>
Always use binding to sanitize input. Avoid introducing
values in queries using string concatenation, which can
produce invalid input and, in some cases, can cause security
issues.
</p>
</div>
<p>
You can use placeholders and the
<code class="literal">
bind()
</code>
method to create saved searches which you can then call with
different values. For example to create a saved search for a
country:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa65128810"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> <span class="token keyword">var</span> myFind <span class="token operator">=</span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token string">"Name = :country"</span><span class="token punctuation">)</span>
<span class="token prompt">mysql-js></span> myFind<span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token string">'country'</span><span class="token punctuation">,</span> <span class="token string">'France'</span><span class="token punctuation">)</span>
<span class="token inlinejson"><span class="token punctuation">{</span>
<span class="token property">"GNP"</span><span class="token operator">:</span> <span class="token number">1424285</span><span class="token punctuation">,</span>
<span class="token property">"_id"</span><span class="token operator">:</span> <span class="token string">"00005de917d80000000000000048"</span><span class="token punctuation">,</span>
<span class="token property">"Code"</span><span class="token operator">:</span> <span class="token string">"FRA"</span><span class="token punctuation">,</span>
<span class="token property">"Name"</span><span class="token operator">:</span> <span class="token string">"France"</span><span class="token punctuation">,</span>
<span class="token property">"IndepYear"</span><span class="token operator">:</span> <span class="token number">843</span><span class="token punctuation">,</span>
<span class="token property">"geography"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Region"</span><span class="token operator">:</span> <span class="token string">"Western Europe"</span><span class="token punctuation">,</span>
<span class="token property">"Continent"</span><span class="token operator">:</span> <span class="token string">"Europe"</span><span class="token punctuation">,</span>
<span class="token property">"SurfaceArea"</span><span class="token operator">:</span> <span class="token number">551500</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"government"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"HeadOfState"</span><span class="token operator">:</span> <span class="token string">"Jacques Chirac"</span><span class="token punctuation">,</span>
<span class="token property">"GovernmentForm"</span><span class="token operator">:</span> <span class="token string">"Republic"</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"demographics"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Population"</span><span class="token operator">:</span> <span class="token number">59225700</span><span class="token punctuation">,</span>
<span class="token property">"LifeExpectancy"</span><span class="token operator">:</span> <span class="token number">78.80000305175781</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span></span>
<span class="token output">1 document in set (0.0028 sec)</span>
<span class="token prompt">mysql-js></span> myFind<span class="token punctuation">.</span><span class="token function">bind</span><span class="token punctuation">(</span><span class="token string">'country'</span><span class="token punctuation">,</span> <span class="token string">'Germany'</span><span class="token punctuation">)</span>
<span class="token inlinejson"><span class="token punctuation">{</span>
<span class="token property">"GNP"</span><span class="token operator">:</span> <span class="token number">2133367</span><span class="token punctuation">,</span>
<span class="token property">"_id"</span><span class="token operator">:</span> <span class="token string">"00005de917d80000000000000038"</span><span class="token punctuation">,</span>
<span class="token property">"Code"</span><span class="token operator">:</span> <span class="token string">"DEU"</span><span class="token punctuation">,</span>
<span class="token property">"Name"</span><span class="token operator">:</span> <span class="token string">"Germany"</span><span class="token punctuation">,</span>
<span class="token property">"IndepYear"</span><span class="token operator">:</span> <span class="token number">1955</span><span class="token punctuation">,</span>
<span class="token property">"geography"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Region"</span><span class="token operator">:</span> <span class="token string">"Western Europe"</span><span class="token punctuation">,</span>
<span class="token property">"Continent"</span><span class="token operator">:</span> <span class="token string">"Europe"</span><span class="token punctuation">,</span>
<span class="token property">"SurfaceArea"</span><span class="token operator">:</span> <span class="token number">357022</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"government"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"HeadOfState"</span><span class="token operator">:</span> <span class="token string">"Johannes Rau"</span><span class="token punctuation">,</span>
<span class="token property">"GovernmentForm"</span><span class="token operator">:</span> <span class="token string">"Federal Republic"</span>
<span class="token punctuation">}</span><span class="token punctuation">,</span>
<span class="token property">"demographics"</span><span class="token operator">:</span> <span class="token punctuation">{</span>
<span class="token property">"Population"</span><span class="token operator">:</span> <span class="token number">82164700</span><span class="token punctuation">,</span>
<span class="token property">"LifeExpectancy"</span><span class="token operator">:</span> <span class="token number">77.4000015258789</span>
<span class="token punctuation">}</span>
<span class="token punctuation">}</span></span>
<span class="token output">1 document in set (0.0026 sec)</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="idm46045127822800">
</a>
Project Results
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127822128">
</a>
<p>
You can return specific fields of a document, instead of
returning all the fields. The following example returns the
GNP and Name fields of all documents in the
<code class="literal">
countryinfo
</code>
collection matching the search
conditions.
</p>
<p>
Use the
<code class="literal">
fields()
</code>
method to pass the list of
fields to return.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa19696706"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token string">"GNP > 5000000"</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">fields</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"GNP"</span><span class="token punctuation">,</span> <span class="token string">"Name"</span><span class="token punctuation">]</span><span class="token punctuation">)</span>
<span class="token inlinejson"><span class="token punctuation">[</span>
<span class="token punctuation">{</span>
<span class="token property">"GNP"</span><span class="token operator">:</span> <span class="token number">8510700</span><span class="token punctuation">,</span>
<span class="token property">"Name"</span><span class="token operator">:</span> <span class="token string">"United States"</span>
<span class="token punctuation">}</span>
<span class="token punctuation">]</span></span>
<span class="token output">1 document in set (0.00 sec)</span></code></pre>
</div>
<p>
In addition, you can alter the returned
documents—adding, renaming, nesting and even computing
new field values—with an expression that describes the
document to return. For example, alter the names of the fields
with the following expression to return only two documents.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa58614433"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">fields</span><span class="token punctuation">(</span>
mysqlx<span class="token punctuation">.</span><span class="token function">expr</span><span class="token punctuation">(</span><span class="token string">'{"Name": upper(Name), "GNPPerCapita": GNP*1000000/demographics.Population}'</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">limit</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">)</span>
<span class="token inlinejson"><span class="token punctuation">{</span>
<span class="token property">"Name"</span><span class="token operator">:</span> <span class="token string">"ARUBA"</span><span class="token punctuation">,</span>
<span class="token property">"GNPPerCapita"</span><span class="token operator">:</span> <span class="token number">8038.834951456311</span>
<span class="token punctuation">}</span>
<span class="token punctuation">{</span>
<span class="token property">"Name"</span><span class="token operator">:</span> <span class="token string">"AFGHANISTAN"</span><span class="token punctuation">,</span>
<span class="token property">"GNPPerCapita"</span><span class="token operator">:</span> <span class="token number">263.0281690140845</span>
<span class="token punctuation">}</span></span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="idm46045127813040">
</a>
Limit, Sort, and Skip Results
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045127812352">
</a>
<p>
You can apply the
<code class="literal">
limit()
</code>
,
<code class="literal">
sort()
</code>
, and
<code class="literal">
skip()
</code>
methods to manage the number and order of documents returned
by the
<code class="literal">
find()
</code>
method.
</p>
<p>
To specify the number of documents included in a result set,
append the
<code class="literal">
limit()
</code>
method with a value to
the
<code class="literal">
find()
</code>
method. The following query
returns the first five documents in the
<code class="literal">
countryinfo
</code>
collection.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa65582705"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">limit</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span>
<span class="token operator">...</span> <span class="token punctuation">[</span><em>output removed</em><span class="token punctuation">]</span>
<span class="token output">5 documents in set (0.00 sec)</span></code></pre>
</div>
<p>
To specify an order for the results, append the
<code class="literal">
sort()
</code>
method to the
<code class="literal">
find()
</code>
method. Pass to the
<code class="literal">
sort()
</code>
method a list of one or more fields
to sort by and, optionally, the descending
(
<code class="literal">
desc
</code>
) or ascending
(
<code class="literal">
asc
</code>
) attribute as appropriate. Ascending
order is the default order type.
</p>
<p>
For example, the following query sorts all documents by the
IndepYear field and then returns the first eight documents in
descending order.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa59708222"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">sort</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"IndepYear desc"</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">limit</span><span class="token punctuation">(</span><span class="token number">8</span><span class="token punctuation">)</span>
<span class="token operator">...</span> <span class="token punctuation">[</span><em>output removed</em><span class="token punctuation">]</span>
<span class="token output">8 documents in set (0.00 sec)</span></code></pre>
</div>
<p>
By default, the
<code class="literal">
limit()
</code>
method starts from
the first document in the collection. You can use the
<code class="literal">
skip()
</code>
method to change the starting
document. For example, to ignore the first document and return
the next eight documents matching the condition, pass to the
<code class="literal">
skip()
</code>
method a value of 1.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-mysqlsh"><div class="docs-select-all right" id="sa43764905"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-mysqlsh"><span class="token prompt">mysql-js></span> db<span class="token punctuation">.</span>countryinfo<span class="token punctuation">.</span><span class="token function">find</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">sort</span><span class="token punctuation">(</span><span class="token punctuation">[</span><span class="token string">"IndepYear desc"</span><span class="token punctuation">]</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">limit</span><span class="token punctuation">(</span><span class="token number">8</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">skip</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span>
<span class="token operator">...</span> <span class="token punctuation">[</span><em>output removed</em><span class="token punctuation">]</span>
<span class="token output">8 documents in set (0.00 sec)</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="idm46045127790304">
</a>
Related Information
</h5>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The
<a class="link" href="functions.html" title="Chapter 14 Functions and Operators">
MySQL Reference
Manual
</a>
provides detailed documentation on functions
and operators.
</p>
</li>
<li class="listitem">
<p>
See
<a class="ulink" href="/doc/x-devapi-userguide/en/crud-ebnf-collection-crud-functions.html#crud-ebnf-collectionfindfunction" target="_top">
CollectionFindFunction
</a>
for
the full syntax definition.
</p>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/ldml-rules.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="ldml-rules">
</a>
12.14.4.2 LDML Syntax Supported in MySQL
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045215060544">
</a>
<p>
This section describes the LDML syntax that MySQL recognizes.
This is a subset of the syntax described in the LDML
specification available at
<a class="ulink" href="http://www.unicode.org/reports/tr35/" target="_blank">
http://www.unicode.org/reports/tr35/
</a>
, which
should be consulted for further information. MySQL recognizes
a large enough subset of the syntax that, in many cases, it is
possible to download a collation definition from the Unicode
Common Locale Data Repository and paste the relevant part
(that is, the part between the
<code class="literal">
<rules>
</code>
and
<code class="literal">
</rules>
</code>
tags) into the MySQL
<code class="filename">
Index.xml
</code>
file. The rules described here
are all supported except that character sorting occurs only at
the primary level. Rules that specify differences at secondary
or higher sort levels are recognized (and thus can be included
in collation definitions) but are treated as equality at the
primary level.
</p>
<p>
The MySQL server generates diagnostics when it finds problems
while parsing the
<code class="filename">
Index.xml
</code>
file. See
<a class="xref" href="collation-diagnostics.html" title="12.14.4.3 Diagnostics During Index.xml Parsing">
Section 12.14.4.3, “Diagnostics During Index.xml Parsing”
</a>
.
</p>
<p>
<span class="bold">
<strong>
Character Representation
</strong>
</span>
</p>
<p>
Characters named in LDML rules can be written literally or in
<code class="literal">
\u
<em class="replaceable">
<code>
nnnn
</code>
</em>
</code>
format,
where
<em class="replaceable">
<code>
nnnn
</code>
</em>
is the hexadecimal
Unicode code point value. For example,
<code class="literal">
A
</code>
and
<code class="literal">
á
</code>
can be written literally or as
<code class="literal">
\u0041
</code>
and
<code class="literal">
\u00E1
</code>
.
Within hexadecimal values, the digits
<code class="literal">
A
</code>
through
<code class="literal">
F
</code>
are not case-sensitive;
<code class="literal">
\u00E1
</code>
and
<code class="literal">
\u00e1
</code>
are
equivalent. For UCA 4.0.0 collations, hexadecimal notation can
be used only for characters in the Basic Multilingual Plane,
not for characters outside the BMP range of
<code class="literal">
0000
</code>
to
<code class="literal">
FFFF
</code>
. For UCA
5.2.0 collations, hexadecimal notation can be used for any
character.
</p>
<p>
The
<code class="filename">
Index.xml
</code>
file itself should be
written using UTF-8 encoding.
</p>
<p>
<span class="bold">
<strong>
Syntax Rules
</strong>
</span>
</p>
<p>
LDML has reset rules and shift rules to specify character
ordering. Orderings are given as a set of rules that begin
with a reset rule that establishes an anchor point, followed
by shift rules that indicate how characters sort relative to
the anchor point.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A
<code class="literal">
<reset>
</code>
rule does not specify
any ordering in and of itself. Instead, it
<span class="quote">
“
<span class="quote">
resets
</span>
”
</span>
the ordering for subsequent shift
rules to cause them to be taken in relation to a given
character. Either of the following rules resets subsequent
shift rules to be taken in relation to the letter
<code class="literal">
'A'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa16353630"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span>A<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span>\u0041<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
The
<code class="literal">
<p>
</code>
,
<code class="literal">
<s>
</code>
, and
<code class="literal">
<t>
</code>
shift rules define primary,
secondary, and tertiary differences of a character from
another character:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Use primary differences to distinguish separate
letters.
</p>
</li>
<li class="listitem">
<p>
Use secondary differences to distinguish accent
variations.
</p>
</li>
<li class="listitem">
<p>
Use tertiary differences to distinguish lettercase
variations.
</p>
</li>
</ul>
</div>
<p>
Either of these rules specifies a primary shift rule for
the
<code class="literal">
'G'
</code>
character:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa12427996"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>p</span><span class="token punctuation">></span></span>G<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>p</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>p</span><span class="token punctuation">></span></span>\u0047<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>p</span><span class="token punctuation">></span></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
The
<code class="literal">
<i>
</code>
shift rule indicates that
one character sorts identically to another. The following
rules cause
<code class="literal">
'b'
</code>
to sort the same as
<code class="literal">
'a'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa50691149"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span>a<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>i</span><span class="token punctuation">></span></span>b<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>i</span><span class="token punctuation">></span></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Abbreviated shift syntax specifies multiple shift rules
using a single pair of tags. The following table shows the
correspondence between abbreviated syntax rules and the
equivalent nonabbreviated rules.
</p>
<div class="table">
<a name="abreviated-shift-syntax">
</a>
<p class="title">
<b>
Table 12.5 Abbreviated Shift Syntax
</b>
</p>
<div class="table-contents">
<table summary="Abbreviated and corresponding nonabbreviated shift syntax rules.">
<colgroup>
<col style="width: 40%"/>
<col style="width: 60%"/>
</colgroup>
<thead>
<tr>
<th>
Abbreviated Syntax
</th>
<th>
Nonabbreviated Syntax
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
<pc>xyz</pc>
</code>
</td>
<td>
<code class="literal">
<p>x</p><p>y</p><p>z</p>
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
<sc>xyz</sc>
</code>
</td>
<td>
<code class="literal">
<s>x</s><s>y</s><s>z</s>
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
<tc>xyz</tc>
</code>
</td>
<td>
<code class="literal">
<t>x</t><t>y</t><t>z</t>
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
<ic>xyz</ic>
</code>
</td>
<td>
<code class="literal">
<i>x</i><i>y</i><i>z</i>
</code>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
</li>
<li class="listitem">
<p>
An expansion is a reset rule that establishes an anchor
point for a multiple-character sequence. MySQL supports
expansions 2 to 6 characters long. The following rules put
<code class="literal">
'z'
</code>
greater at the primary level than
the sequence of three characters
<code class="literal">
'abc'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa48702883"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span>abc<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>p</span><span class="token punctuation">></span></span>z<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>p</span><span class="token punctuation">></span></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
A contraction is a shift rule that sorts a
multiple-character sequence. MySQL supports contractions 2
to 6 characters long. The following rules put the sequence
of three characters
<code class="literal">
'xyz'
</code>
greater at
the primary level than
<code class="literal">
'a'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa44079442"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span>a<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>p</span><span class="token punctuation">></span></span>xyz<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>p</span><span class="token punctuation">></span></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Long expansions and long contractions can be used
together. These rules put the sequence of three characters
<code class="literal">
'xyz'
</code>
greater at the primary level than
the sequence of three characters
<code class="literal">
'abc'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa40078073"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span>abc<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>p</span><span class="token punctuation">></span></span>xyz<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>p</span><span class="token punctuation">></span></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Normal expansion syntax uses
<code class="literal">
<x>
</code>
plus
<code class="literal">
<extend>
</code>
elements to specify
an expansion. The following rules put the character
<code class="literal">
'k'
</code>
greater at the secondary level than
the sequence
<code class="literal">
'ch'
</code>
. That is,
<code class="literal">
'k'
</code>
behaves as if it expands to a
character after
<code class="literal">
'c'
</code>
followed by
<code class="literal">
'h'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa99695074"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span>c<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>x</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>s</span><span class="token punctuation">></span></span>k<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>s</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>extend</span><span class="token punctuation">></span></span>h<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>extend</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>x</span><span class="token punctuation">></span></span></code></pre>
</div>
<p>
This syntax permits long sequences. These rules sort the
sequence
<code class="literal">
'ccs'
</code>
greater at the tertiary
level than the sequence
<code class="literal">
'cscs'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa46665990"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span>cs<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>x</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>t</span><span class="token punctuation">></span></span>ccs<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>t</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>extend</span><span class="token punctuation">></span></span>cs<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>extend</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>x</span><span class="token punctuation">></span></span></code></pre>
</div>
<p>
The LDML specification describes normal expansion syntax
as
<span class="quote">
“
<span class="quote">
tricky.
</span>
”
</span>
See that specification for
details.
</p>
</li>
<li class="listitem">
<p>
Previous context syntax uses
<code class="literal">
<x>
</code>
plus
<code class="literal">
<context>
</code>
elements to
specify that the context before a character affects how it
sorts. The following rules put
<code class="literal">
'-'
</code>
greater at the secondary level than
<code class="literal">
'a'
</code>
, but only when
<code class="literal">
'-'
</code>
occurs after
<code class="literal">
'b'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa88155943"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span>a<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>x</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>context</span><span class="token punctuation">></span></span>b<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>context</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>s</span><span class="token punctuation">></span></span>-<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>s</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>x</span><span class="token punctuation">></span></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Previous context syntax can include the
<code class="literal">
<extend>
</code>
element. These rules put
<code class="literal">
'def'
</code>
greater at the primary level than
<code class="literal">
'aghi'
</code>
, but only when
<code class="literal">
'def'
</code>
comes after
<code class="literal">
'abc'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa70885827"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span>a<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>x</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>context</span><span class="token punctuation">></span></span>abc<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>context</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>p</span><span class="token punctuation">></span></span>def<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>p</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>extend</span><span class="token punctuation">></span></span>ghi<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>extend</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>x</span><span class="token punctuation">></span></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Reset rules permit a
<code class="literal">
before
</code>
attribute.
Normally, shift rules after a reset rule indicate
characters that sort after the reset character. Shift
rules after a reset rule that has the
<code class="literal">
before
</code>
attribute indicate characters
that sort before the reset character. The following rules
put the character
<code class="literal">
'b'
</code>
immediately
before
<code class="literal">
'a'
</code>
at the primary level:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa9601871"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span> <span class="token attr-name">before</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>primary<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>a<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>p</span><span class="token punctuation">></span></span>b<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>p</span><span class="token punctuation">></span></span></code></pre>
</div>
<p>
Permissible
<code class="literal">
before
</code>
attribute values
specify the sort level by name or the equivalent numeric
value:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa43912994"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span> <span class="token attr-name">before</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>primary<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span> <span class="token attr-name">before</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>1<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span> <span class="token attr-name">before</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>secondary<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span> <span class="token attr-name">before</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>2<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span> <span class="token attr-name">before</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>tertiary<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span> <span class="token attr-name">before</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>3<span class="token punctuation">"</span></span><span class="token punctuation">></span></span></code></pre>
</div>
</li>
<li class="listitem">
<p>
A reset rule can name a logical reset position rather than
a literal character:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa16695479"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>first_tertiary_ignorable</span><span class="token punctuation">/></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>last_tertiary_ignorable</span><span class="token punctuation">/></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>first_secondary_ignorable</span><span class="token punctuation">/></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>last_secondary_ignorable</span><span class="token punctuation">/></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>first_primary_ignorable</span><span class="token punctuation">/></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>last_primary_ignorable</span><span class="token punctuation">/></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>first_variable</span><span class="token punctuation">/></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>last_variable</span><span class="token punctuation">/></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>first_non_ignorable</span><span class="token punctuation">/></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>last_non_ignorable</span><span class="token punctuation">/></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>first_trailing</span><span class="token punctuation">/></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>last_trailing</span><span class="token punctuation">/></span></span></code></pre>
</div>
<p>
These rules put
<code class="literal">
'z'
</code>
greater at the
primary level than nonignorable characters that have a
Default Unicode Collation Element Table (DUCET) entry and
that are not CJK:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa27369716"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>last_non_ignorable</span><span class="token punctuation">/></span></span><span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>p</span><span class="token punctuation">></span></span>z<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>p</span><span class="token punctuation">></span></span></code></pre>
</div>
<p>
Logical positions have the code points shown in the
following table.
</p>
<div class="table">
<a name="logical-reset-position-code-points">
</a>
<p class="title">
<b>
Table 12.6 Logical Reset Position Code Points
</b>
</p>
<div class="table-contents">
<table summary="Logical positions and Unicode 4.0.0 and Unicode 5.2.0 code points.">
<colgroup>
<col style="width: 40%"/>
<col style="width: 30%"/>
<col style="width: 30%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Logical Position
</th>
<th scope="col">
Unicode 4.0.0 Code Point
</th>
<th scope="col">
Unicode 5.2.0 Code Point
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
<code class="literal">
<first_non_ignorable/>
</code>
</th>
<td>
U+02D0
</td>
<td>
U+02D0
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
<last_non_ignorable/>
</code>
</th>
<td>
U+A48C
</td>
<td>
U+1342E
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
<first_primary_ignorable/>
</code>
</th>
<td>
U+0332
</td>
<td>
U+0332
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
<last_primary_ignorable/>
</code>
</th>
<td>
U+20EA
</td>
<td>
U+101FD
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
<first_secondary_ignorable/>
</code>
</th>
<td>
U+0000
</td>
<td>
U+0000
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
<last_secondary_ignorable/>
</code>
</th>
<td>
U+FE73
</td>
<td>
U+FE73
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
<first_tertiary_ignorable/>
</code>
</th>
<td>
U+0000
</td>
<td>
U+0000
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
<last_tertiary_ignorable/>
</code>
</th>
<td>
U+FE73
</td>
<td>
U+FE73
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
<first_trailing/>
</code>
</th>
<td>
U+0000
</td>
<td>
U+0000
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
<last_trailing/>
</code>
</th>
<td>
U+0000
</td>
<td>
U+0000
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
<first_variable/>
</code>
</th>
<td>
U+0009
</td>
<td>
U+0009
</td>
</tr>
<tr>
<th scope="row">
<code class="literal">
<last_variable/>
</code>
</th>
<td>
U+2183
</td>
<td>
U+1D371
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 431px; width: 607px;">
<thead>
<tr>
<th scope="col" style="width: 242.281px;">
Logical Position
</th>
<th scope="col" style="width: 181.703px;">
Unicode 4.0.0 Code Point
</th>
<th scope="col" style="width: 181.734px;">
Unicode 5.2.0 Code Point
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
</li>
<li class="listitem">
<p>
The
<code class="literal">
<collation>
</code>
element permits a
<code class="literal">
shift-after-method
</code>
attribute that
affects character weight calculation for shift rules. The
attribute has these permitted values:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
simple
</code>
: Calculate character weights
as for reset rules that do not have a
<code class="literal">
before
</code>
attribute. This is the
default if the attribute is not given.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
expand
</code>
: Use expansions for shifts
after reset rules.
</p>
</li>
</ul>
</div>
<p>
Suppose that
<code class="literal">
'0'
</code>
and
<code class="literal">
'1'
</code>
have weights of
<code class="literal">
0E29
</code>
and
<code class="literal">
0E2A
</code>
and we
want to put all basic Latin letters between
<code class="literal">
'0'
</code>
and
<code class="literal">
'1'
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa85076258"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>reset</span><span class="token punctuation">></span></span>0<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>reset</span><span class="token punctuation">></span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation"><</span>pc</span><span class="token punctuation">></span></span>abcdefghijklmnopqrstuvwxyz<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>pc</span><span class="token punctuation">></span></span></code></pre>
</div>
<p>
For simple shift mode, weights are calculated as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa11454493"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">'a' has weight 0E29+1
'b' has weight 0E29+2
'c' has weight 0E29+3
...</code></pre>
</div>
<p>
However, there are not enough vacant positions to put 26
characters between
<code class="literal">
'0'
</code>
and
<code class="literal">
'1'
</code>
. The result is that digits and
letters are intermixed.
</p>
<p>
To solve this, use
<code class="literal">
shift-after-method="expand"
</code>
. Then
weights are calculated like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa29372544"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">'a' has weight [0E29][233D+1]
'b' has weight [0E29][233D+2]
'c' has weight [0E29][233D+3]
...</code></pre>
</div>
<p>
<code class="literal">
233D
</code>
is the UCA 4.0.0 weight for
character
<code class="literal">
0xA48C
</code>
, which is the last
nonignorable character (a sort of the greatest character
in the collation, excluding CJK). UCA 5.2.0 is similar but
uses
<code class="literal">
3ACA
</code>
, for character
<code class="literal">
0x1342E
</code>
.
</p>
</li>
</ul>
</div>
<p>
<span class="bold">
<strong>
MySQL-Specific LDML
Extensions
</strong>
</span>
</p>
<p>
An extension to LDML rules permits the
<code class="literal">
<collation>
</code>
element to include an
optional
<code class="literal">
version
</code>
attribute in
<code class="literal">
<collation>
</code>
tags to indicate the UCA
version on which the collation is based. If the
<code class="literal">
version
</code>
attribute is omitted, its default
value is
<code class="literal">
4.0.0
</code>
. For example, this
specification indicates a collation that is based on UCA
5.2.0:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-xml"><div class="docs-select-all right" id="sa77918906"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-xml"><span class="token tag"><span class="token tag"><span class="token punctuation"><</span>collation</span> <span class="token attr-name">id</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span><em class="replaceable">nnn</em><span class="token punctuation">"</span></span> <span class="token attr-name">name</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>utf8mb4_<em class="replaceable">xxx</em>_ci<span class="token punctuation">"</span></span> <span class="token attr-name">version</span><span class="token attr-value"><span class="token punctuation">=</span><span class="token punctuation">"</span>5.2.0<span class="token punctuation">"</span></span><span class="token punctuation">></span></span>
...
<span class="token tag"><span class="token tag"><span class="token punctuation"></</span>collation</span><span class="token punctuation">></span></span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-check-availability.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="innodb-check-availability">
</a>
17.1.3 Verifying that InnoDB is the Default Storage Engine
</h3>
</div>
</div>
</div>
<p>
Issue a
<a class="link" href="show-engines.html" title="15.7.7.17 SHOW ENGINES Statement">
<code class="literal">
SHOW ENGINES
</code>
</a>
statement to
view the available MySQL storage engines. Look for
<code class="literal">
DEFAULT
</code>
in the
<code class="literal">
SUPPORT
</code>
column.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa63875120"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">ENGINES</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Alternatively, query the Information Schema
<a class="link" href="information-schema-engines-table.html" title="28.3.13 The INFORMATION_SCHEMA ENGINES Table">
<code class="literal">
ENGINES
</code>
</a>
table.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa20686110"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span><span class="token keyword">ENGINES</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-disabling-tablespace-path-validation.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="innodb-disabling-tablespace-path-validation">
</a>
17.6.3.7 Disabling Tablespace Path Validation
</h4>
</div>
</div>
</div>
<p>
At startup,
<code class="literal">
InnoDB
</code>
scans directories defined by
the
<a class="link" href="innodb-parameters.html#sysvar_innodb_directories">
<code class="literal">
innodb_directories
</code>
</a>
variable
for tablespace files. The paths of discovered tablespace files are
validated against the paths recorded in the data dictionary. If
the paths do not match, the paths in the data dictionary are
updated.
</p>
<p>
The
<a class="link" href="innodb-parameters.html#sysvar_innodb_validate_tablespace_paths">
<code class="literal">
innodb_validate_tablespace_paths
</code>
</a>
variable permits disabling tablespace path validation. This
feature is intended for environments where tablespaces files are
not moved. Disabling path validation improves startup time on
systems with a large number of tablespace files. If
<a class="link" href="server-system-variables.html#sysvar_log_error_verbosity">
<code class="literal">
log_error_verbosity
</code>
</a>
is set to 3,
the following message is printed at startup when tablespace path
validation is disabled:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa95487896"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token punctuation">[</span>InnoDB<span class="token punctuation">]</span> Skipping InnoDB tablespace path validation<span class="token punctuation">.</span>
Manually moved tablespace files will not be detected!</code></pre>
</div>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
Starting the server with tablespace path validation disabled
after moving tablespace files can lead to undefined behavior.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-single-user-mode.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysql-cluster-single-user-mode">
</a>
25.6.6 NDB Cluster Single User Mode
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045092503392">
</a>
<a class="indexterm" name="idm46045092501904">
</a>
<p>
<span class="firstterm">
Single user mode
</span>
enables the
database administrator to restrict access to the database system
to a single API node, such as a MySQL server (SQL node) or an
instance of
<a class="link" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup">
<span class="command">
<strong>
ndb_restore
</strong>
</span>
</a>
. When entering single
user mode, connections to all other API nodes are closed
gracefully and all running transactions are aborted. No new
transactions are permitted to start.
</p>
<p>
Once the cluster has entered single user mode, only the designated
API node is granted access to the database.
</p>
<p>
You can use the
<code class="literal">
ALL STATUS
</code>
command in the
<a class="link" href="mysql-cluster-programs-ndb-mgm.html" title="25.5.5 ndb_mgm — The NDB Cluster Management Client">
<span class="command">
<strong>
ndb_mgm
</strong>
</span>
</a>
client to see when the cluster has
entered single user mode. You can also check the
<code class="literal">
status
</code>
column of the
<a class="link" href="mysql-cluster-ndbinfo-nodes.html" title="25.6.17.48 The ndbinfo nodes Table">
<code class="literal">
ndbinfo.nodes
</code>
</a>
table (see
<a class="xref" href="mysql-cluster-ndbinfo-nodes.html" title="25.6.17.48 The ndbinfo nodes Table">
Section 25.6.17.48, “The ndbinfo nodes Table”
</a>
, for more
information).
</p>
<p>
Example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-ndbmgm"><div class="docs-select-all right" id="sa95678237"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ndbmgm"><span class="token prompt">ndb_mgm></span> <span class="token keyword">ENTER SINGLE USER MODE</span> 5</code></pre>
</div>
<p>
After this command has executed and the cluster has entered single
user mode, the API node whose node ID is
<code class="literal">
5
</code>
becomes the cluster's only permitted user.
</p>
<p>
The node specified in the preceding command must be an API node;
attempting to specify any other type of node is rejected.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
When the preceding command is invoked, all transactions running
on the designated node are aborted, the connection is closed,
and the server must be restarted.
</p>
</div>
<p>
The command
<code class="literal">
EXIT SINGLE USER MODE
</code>
changes the
state of the cluster's data nodes from single user mode to
normal mode. API nodes—such as MySQL Servers—waiting
for a connection (that is, waiting for the cluster to become ready
and available), are again permitted to connect. The API node
denoted as the single-user node continues to run (if still
connected) during and after the state change.
</p>
<p>
Example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-ndbmgm"><div class="docs-select-all right" id="sa91001271"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ndbmgm"><span class="token prompt">ndb_mgm></span> <span class="token keyword">EXIT SINGLE USER MODE</span></code></pre>
</div>
<a class="indexterm" name="idm46045092483568">
</a>
<p>
There are two recommended ways to handle a node failure when
running in single user mode:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Method 1:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Finish all single user mode transactions
</p>
</li>
<li class="listitem">
<p>
Issue the
<code class="literal">
EXIT SINGLE USER MODE
</code>
command
</p>
</li>
<li class="listitem">
<p>
Restart the cluster's data nodes
</p>
</li>
</ol>
</div>
</li>
<li class="listitem">
<p>
Method 2:
</p>
<p>
Restart storage nodes prior to entering single user mode.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/year.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="year">
</a>
13.2.4 The YEAR Type
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045213518416">
</a>
<a class="indexterm" name="idm46045213517344">
</a>
<p>
The
<code class="literal">
YEAR
</code>
type is a 1-byte type used to
represent year values. It can be declared as
<code class="literal">
YEAR
</code>
with an implicit display width of 4
characters, or equivalently as
<code class="literal">
YEAR(4)
</code>
with
an explicit display width.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
he
<a class="link" href="year.html" title="13.2.4 The YEAR Type">
<code class="literal">
YEAR(4)
</code>
</a>
data type using an
explicit display width is deprecated and you should expect
support for it to be removed in a future version of MySQL.
Instead, use
<a class="link" href="year.html" title="13.2.4 The YEAR Type">
<code class="literal">
YEAR
</code>
</a>
without a
display width, which has the same meaning.
</p>
</div>
<p>
MySQL displays
<code class="literal">
YEAR
</code>
values in
<em class="replaceable">
<code>
YYYY
</code>
</em>
format, with a range of
<code class="literal">
1901
</code>
to
<code class="literal">
2155
</code>
, and
<code class="literal">
0000
</code>
.
</p>
<p>
<code class="literal">
YEAR
</code>
accepts input values in a variety of
formats:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
As 4-digit strings in the range
<code class="literal">
'1901'
</code>
to
<code class="literal">
'2155'
</code>
.
</p>
</li>
<li class="listitem">
<p>
As 4-digit numbers in the range
<code class="literal">
1901
</code>
to
<code class="literal">
2155
</code>
.
</p>
</li>
<li class="listitem">
<p>
As 1- or 2-digit strings in the range
<code class="literal">
'0'
</code>
to
<code class="literal">
'99'
</code>
. MySQL converts values in the
ranges
<code class="literal">
'0'
</code>
to
<code class="literal">
'69'
</code>
and
<code class="literal">
'70'
</code>
to
<code class="literal">
'99'
</code>
to
<code class="literal">
YEAR
</code>
values in the ranges
<code class="literal">
2000
</code>
to
<code class="literal">
2069
</code>
and
<code class="literal">
1970
</code>
to
<code class="literal">
1999
</code>
.
</p>
</li>
<li class="listitem">
<p>
As 1- or 2-digit numbers in the range
<code class="literal">
0
</code>
to
<code class="literal">
99
</code>
. MySQL converts values in the
ranges
<code class="literal">
1
</code>
to
<code class="literal">
69
</code>
and
<code class="literal">
70
</code>
to
<code class="literal">
99
</code>
to
<code class="literal">
YEAR
</code>
values in the ranges
<code class="literal">
2001
</code>
to
<code class="literal">
2069
</code>
and
<code class="literal">
1970
</code>
to
<code class="literal">
1999
</code>
.
</p>
<p>
The result of inserting a numeric
<code class="literal">
0
</code>
has a
display value of
<code class="literal">
0000
</code>
and an internal
value of
<code class="literal">
0000
</code>
. To insert zero and have it
be interpreted as
<code class="literal">
2000
</code>
, specify it as a
string
<code class="literal">
'0'
</code>
or
<code class="literal">
'00'
</code>
.
</p>
</li>
<li class="listitem">
<p>
As the result of functions that return a value that is
acceptable in
<code class="literal">
YEAR
</code>
context, such as
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
.
</p>
</li>
</ul>
</div>
<p>
If strict SQL mode is not enabled, MySQL converts invalid
<code class="literal">
YEAR
</code>
values to
<code class="literal">
0000
</code>
. In
strict SQL mode, attempting to insert an invalid
<code class="literal">
YEAR
</code>
value produces an error.
</p>
<p>
See also
<a class="xref" href="two-digit-years.html" title="13.2.9 2-Digit Years in Dates">
Section 13.2.9, “2-Digit Years in Dates”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-privilege-checks-account.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-privilege-checks-account">
</a>
19.3.3.1 Privileges For The Replication PRIVILEGE_CHECKS_USER Account
</h4>
</div>
</div>
</div>
<p>
The user account that is specified using the
<a class="link" href="change-replication-source-to.html" title="15.4.2.2 CHANGE REPLICATION SOURCE TO Statement">
<code class="literal">
CHANGE REPLICATION SOURCE TO
</code>
</a>
statement as the
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account for a replication channel must have the
<a class="link" href="privileges-provided.html#priv_replication-applier">
<code class="literal">
REPLICATION_APPLIER
</code>
</a>
privilege,
otherwise the replication applier thread does not start. As
explained in
<a class="xref" href="replication-privilege-checks.html" title="19.3.3 Replication Privilege Checks">
Section 19.3.3, “Replication Privilege Checks”
</a>
, the
account requires further privileges that are sufficient to apply
all the expected transactions expected on the replication
channel. These privileges are checked only when relevant
transactions are executed.
</p>
<p>
The use of row-based binary logging
(
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=ROW
</code>
</a>
) is strongly
recommended for replication channels that are secured using a
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account. With
statement-based binary logging, some administrator-level
privileges might be required for the
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account to execute
transactions successfully. The
<code class="literal">
REQUIRE_ROW_FORMAT
</code>
setting can be applied to
secured channels, which restricts the channel from executing
events that would require these privileges.
</p>
<p>
The
<a class="link" href="privileges-provided.html#priv_replication-applier">
<code class="literal">
REPLICATION_APPLIER
</code>
</a>
privilege
explicitly or implicitly allows the
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account to carry out
the following operations that a replication thread needs to
perform:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Setting the value of the system variables
<a class="link" href="replication-options-gtids.html#sysvar_gtid_next">
<code class="literal">
gtid_next
</code>
</a>
,
<a class="link" href="replication-options-binary-log.html#sysvar_original_commit_timestamp">
<code class="literal">
original_commit_timestamp
</code>
</a>
,
<a class="link" href="replication-options-source.html#sysvar_original_server_version">
<code class="literal">
original_server_version
</code>
</a>
,
<a class="link" href="replication-options-source.html#sysvar_immediate_server_version">
<code class="literal">
immediate_server_version
</code>
</a>
,
and
<a class="link" href="server-system-variables.html#sysvar_pseudo_replica_mode">
<code class="literal">
pseudo_replica_mode
</code>
</a>
, to
apply appropriate metadata and behaviors when executing
transactions.
</p>
</li>
<li class="listitem">
<p>
Executing internal-use
<a class="link" href="binlog.html" title="15.7.8.1 BINLOG Statement">
<code class="literal">
BINLOG
</code>
</a>
statements to apply
<a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
<span class="command">
<strong>
mysqlbinlog
</strong>
</span>
</a>
output,
provided that the account also has permission for the tables
and operations in those statements.
</p>
</li>
<li class="listitem">
<p>
Updating the system tables
<code class="literal">
mysql.gtid_executed
</code>
,
<code class="literal">
mysql.slave_relay_log_info
</code>
,
<code class="literal">
mysql.slave_worker_info
</code>
, and
<code class="literal">
mysql.slave_master_info
</code>
, to update
replication metadata. (If events access these tables
explicitly for other purposes, you must grant the
appropriate privileges on the tables.)
</p>
</li>
<li class="listitem">
<p>
Applying a binary log
<code class="literal">
Table_map_log_event
</code>
, which provides table
metadata but does not make any database changes.
</p>
</li>
</ul>
</div>
<p>
If the
<code class="literal">
REQUIRE_TABLE_PRIMARY_KEY_CHECK
</code>
option
of the
<a class="link" href="change-replication-source-to.html" title="15.4.2.2 CHANGE REPLICATION SOURCE TO Statement">
<code class="literal">
CHANGE REPLICATION SOURCE
TO
</code>
</a>
statement is set to the default value
<code class="literal">
STREAM
</code>
, the
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account needs
privileges sufficient to set restricted session variables, so
that it can change the value of the
<a class="link" href="server-system-variables.html#sysvar_sql_require_primary_key">
<code class="literal">
sql_require_primary_key
</code>
</a>
system
variable for the duration of a session to match the setting
replicated from the source. The
<a class="link" href="privileges-provided.html#priv_session-variables-admin">
<code class="literal">
SESSION_VARIABLES_ADMIN
</code>
</a>
privilege
gives the account this capability. This privilege also allows
the account to apply
<a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
<span class="command">
<strong>
mysqlbinlog
</strong>
</span>
</a>
output that
was created using the
<a class="link" href="mysqlbinlog.html#option_mysqlbinlog_disable-log-bin">
<code class="option">
--disable-log-bin
</code>
</a>
option. If
you set
<code class="literal">
REQUIRE_TABLE_PRIMARY_KEY_CHECK
</code>
to
either
<code class="literal">
ON
</code>
or
<code class="literal">
OFF
</code>
, the
replica always uses that value for the
<a class="link" href="server-system-variables.html#sysvar_sql_require_primary_key">
<code class="literal">
sql_require_primary_key
</code>
</a>
system
variable in replication operations, and so does not need these
session administration level privileges.
</p>
<p>
If table encryption is in use, the
<a class="link" href="server-system-variables.html#sysvar_table_encryption_privilege_check">
<code class="literal">
table_encryption_privilege_check
</code>
</a>
system variable is set to
<code class="literal">
ON
</code>
, and the
encryption setting for the tablespace involved in any event
differs from the applying server's default encryption setting
(specified by the
<a class="link" href="server-system-variables.html#sysvar_default_table_encryption">
<code class="literal">
default_table_encryption
</code>
</a>
system
variable), the
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account
needs the
<a class="link" href="privileges-provided.html#priv_table-encryption-admin">
<code class="literal">
TABLE_ENCRYPTION_ADMIN
</code>
</a>
privilege in order to override the default encryption setting.
It is strongly recommended that you do not grant this privilege.
Instead, ensure that the default encryption setting on a replica
matches the encryption status of the tablespaces that it
replicates, and that replication group members have the same
default encryption setting, so that the privilege is not needed.
</p>
<p>
In order to execute specific replicated transactions from the
relay log, or transactions from
<a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
<span class="command">
<strong>
mysqlbinlog
</strong>
</span>
</a>
output as required, the
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account must have the following privileges:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
For a row insertion logged in row format (which are logged
as a
<code class="literal">
Write_rows_log_event
</code>
), the
<a class="link" href="privileges-provided.html#priv_insert">
<code class="literal">
INSERT
</code>
</a>
privilege on the
relevant table.
</p>
</li>
<li class="listitem">
<p>
For a row update logged in row format (which are logged as
an
<code class="literal">
Update_rows_log_event
</code>
), the
<a class="link" href="privileges-provided.html#priv_update">
<code class="literal">
UPDATE
</code>
</a>
privilege on the
relevant table.
</p>
</li>
<li class="listitem">
<p>
For a row deletion logged in row format (which are logged as
a
<code class="literal">
Delete_rows_log_event
</code>
), the
<a class="link" href="privileges-provided.html#priv_delete">
<code class="literal">
DELETE
</code>
</a>
privilege on the
relevant table.
</p>
</li>
</ul>
</div>
<p>
If statement-based binary logging is in use (which is not
recommended with a
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account), for a transaction control statement such as
<code class="literal">
BEGIN
</code>
or
<code class="literal">
COMMIT
</code>
or DML
logged in statement format (which are logged as a
<code class="literal">
Query_log_event
</code>
), the
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account needs
privileges to execute the statement contained in the event.
</p>
<p>
If
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD DATA
</code>
</a>
operations need to
be carried out on the replication channel, use row-based binary
logging (
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=ROW
</code>
</a>
).
With this logging format, the
<a class="link" href="privileges-provided.html#priv_file">
<code class="literal">
FILE
</code>
</a>
privilege is not needed to
execute the event, so do not give the
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account this privilege.
The use of row-based binary logging is strongly recommended with
replication channels that are secured using a
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account. If
<code class="literal">
REQUIRE_ROW_FORMAT
</code>
is set for the channel,
row-based binary logging is required. The
<code class="literal">
Format_description_log_event
</code>
, which deletes
any temporary files created by
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD
DATA
</code>
</a>
events, is processed without privilege checks.
For more information, see
<a class="xref" href="replication-features-load-data.html" title="19.5.1.19 Replication and LOAD DATA">
Section 19.5.1.19, “Replication and LOAD DATA”
</a>
.
</p>
<p>
If the
<a class="link" href="replication-options-replica.html#sysvar_init_replica">
<code class="literal">
init_replica
</code>
</a>
system
variable is set to specify one or more SQL statements to be
executed when the replication SQL thread starts, the
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account must have the
privileges needed to execute these statements.
</p>
<p>
It is recommended that you never give any ACL privileges to the
<code class="literal">
PRIVILEGE_CHECKS_USER
</code>
account, including
<a class="link" href="privileges-provided.html#priv_create-user">
<code class="literal">
CREATE USER
</code>
</a>
,
<a class="link" href="privileges-provided.html#priv_create-role">
<code class="literal">
CREATE ROLE
</code>
</a>
,
<a class="link" href="privileges-provided.html#priv_drop-role">
<code class="literal">
DROP ROLE
</code>
</a>
, and
<a class="link" href="privileges-provided.html#priv_grant-option">
<code class="literal">
GRANT OPTION
</code>
</a>
, and do not permit
the account to update the
<code class="literal">
mysql.user
</code>
table.
With these privileges, the account could be used to create or
modify user accounts on the server. To avoid ACL statements
issued on the source server being replicated to the secured
channel for execution (where they fail in the absence of these
privileges), you can issue
<code class="literal">
SET sql_log_bin =
0
</code>
before all ACL statements and
<code class="literal">
SET
sql_log_bin = 1
</code>
after them, to omit the statements
from the source's binary log. Alternatively, you can set a
dedicated current database before executing all ACL statements,
and use a replication filter
(
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db">
<code class="option">
--binlog-ignore-db
</code>
</a>
) to filter
out this database on the replica.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-install-windows-binary.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-install-windows-binary">
</a>
25.3.2.1 Installing NDB Cluster on Windows from a Binary Release
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045122578256">
</a>
<a class="indexterm" name="idm46045122576768">
</a>
<p>
This section describes a basic installation of NDB Cluster on
Windows using a binary
<span class="quote">
“
<span class="quote">
no-install
</span>
”
</span>
NDB Cluster
release provided by Oracle, using the same 4-node setup outlined
in the beginning of this section (see
<a class="xref" href="mysql-cluster-installation.html" title="25.3 NDB Cluster Installation">
Section 25.3, “NDB Cluster Installation”
</a>
), as shown in the
following table:
</p>
<div class="table">
<a name="idm46045122572576">
</a>
<p class="title">
<b>
Table 25.6 Network addresses of nodes in example cluster
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<thead>
<tr>
<th>
Node
</th>
<th>
IP Address
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
Management node (
<span class="command">
<strong>
mgmd
</strong>
</span>
)
</td>
<td>
198.51.100.10
</td>
</tr>
<tr>
<td>
SQL node (
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
)
</td>
<td>
198.51.100.20
</td>
</tr>
<tr>
<td>
Data node "A" (
<a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon">
<span class="command">
<strong>
ndbd
</strong>
</span>
</a>
)
</td>
<td>
198.51.100.30
</td>
</tr>
<tr>
<td>
Data node "B" (
<a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon">
<span class="command">
<strong>
ndbd
</strong>
</span>
</a>
)
</td>
<td>
198.51.100.40
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>
As on other platforms, the NDB Cluster host computer running an
SQL node must have installed on it a MySQL Server binary
(
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld.exe
</strong>
</span>
</a>
). You should also have the MySQL
client (
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql.exe
</strong>
</span>
</a>
) on this host. For
management nodes and data nodes, it is not necessary to install
the MySQL Server binary; however, each management node requires
the management server daemon (
<a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon">
<span class="command">
<strong>
ndb_mgmd.exe
</strong>
</span>
</a>
);
each data node requires the data node daemon
(
<a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon">
<span class="command">
<strong>
ndbd.exe
</strong>
</span>
</a>
or
<a class="link" href="mysql-cluster-programs-ndbmtd.html" title="25.5.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)">
<span class="command">
<strong>
ndbmtd.exe
</strong>
</span>
</a>
).
For this example, we refer to
<a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon">
<span class="command">
<strong>
ndbd.exe
</strong>
</span>
</a>
as the
data node executable, but you can install
<a class="link" href="mysql-cluster-programs-ndbmtd.html" title="25.5.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)">
<span class="command">
<strong>
ndbmtd.exe
</strong>
</span>
</a>
, the multithreaded version of this
program, instead, in exactly the same way. You should also
install the management client (
<a class="link" href="mysql-cluster-programs-ndb-mgm.html" title="25.5.5 ndb_mgm — The NDB Cluster Management Client">
<span class="command">
<strong>
ndb_mgm.exe
</strong>
</span>
</a>
)
on the management server host. This section covers the steps
necessary to install the correct Windows binaries for each type
of NDB Cluster node.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
As with other Windows programs, NDB Cluster executables are
named with the
<code class="filename">
.exe
</code>
file extension.
However, it is not necessary to include the
<code class="filename">
.exe
</code>
extension when invoking these
programs from the command line. Therefore, we often simply
refer to these programs in this documentation as
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
,
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
,
<a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon">
<span class="command">
<strong>
ndb_mgmd
</strong>
</span>
</a>
, and so on. You should understand
that, whether we refer (for example) to
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
or
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld.exe
</strong>
</span>
</a>
,
either name means the same thing (the MySQL Server program).
</p>
</div>
<p>
For setting up an NDB Cluster using Oracles's
<code class="literal">
no-install
</code>
binaries, the first step in the
installation process is to download the latest NDB Cluster
Windows ZIP binary archive from
<a class="ulink" href="https://dev.mysql.com/downloads/cluster/" target="_top">
https://dev.mysql.com/downloads/cluster/
</a>
. This archive has a
filename of the
<code class="filename">
mysql-cluster-gpl-
<em class="replaceable">
<code>
ver
</code>
</em>
-win
<em class="replaceable">
<code>
arch
</code>
</em>
.zip
</code>
,
where
<em class="replaceable">
<code>
ver
</code>
</em>
is the
<code class="literal">
NDB
</code>
storage engine version (such as
<code class="literal">
8.4.0
</code>
), and
<em class="replaceable">
<code>
arch
</code>
</em>
is the architecture
(
<code class="literal">
32
</code>
for 32-bit binaries, and
<code class="literal">
64
</code>
for 64-bit binaries). For example, the NDB
Cluster 8.4.0 archive for 64-bit Windows
systems is named
<code class="filename">
mysql-cluster-gpl-8.4.0-win64.zip
</code>
.
</p>
<p>
You can run 32-bit NDB Cluster binaries on both 32-bit and
64-bit versions of Windows; however, 64-bit NDB Cluster binaries
can be used only on 64-bit versions of Windows. If you are using
a 32-bit version of Windows on a computer that has a 64-bit CPU,
then you must use the 32-bit NDB Cluster binaries.
</p>
<p>
To minimize the number of files that need to be downloaded from
the Internet or copied between machines, we start with the
computer where you intend to run the SQL node.
</p>
<p>
<b>
SQL node.
</b>
We assume that you have placed a copy of the archive in the
directory
<code class="filename">
C:\Documents and
Settings\
<em class="replaceable">
<code>
username
</code>
</em>
\My
Documents\Downloads
</code>
on the computer having the IP
address 198.51.100.20, where
<em class="replaceable">
<code>
username
</code>
</em>
is the name of the current
user. (You can obtain this name using
<code class="literal">
ECHO
%USERNAME%
</code>
on the command line.) To install and run
NDB Cluster executables as Windows services, this user should
be a member of the
<code class="literal">
Administrators
</code>
group.
</p>
<p>
Extract all the files from the archive. The Extraction Wizard
integrated with Windows Explorer is adequate for this task. (If
you use a different archive program, be sure that it extracts
all files and directories from the archive, and that it
preserves the archive's directory structure.) When you are
asked for a destination directory, enter
<code class="filename">
C:\
</code>
, which causes the Extraction Wizard to
extract the archive to the directory
<code class="filename">
C:\mysql-cluster-gpl-
<em class="replaceable">
<code>
ver
</code>
</em>
-win
<em class="replaceable">
<code>
arch
</code>
</em>
</code>
.
Rename this directory to
<code class="filename">
C:\mysql
</code>
.
</p>
<p>
It is possible to install the NDB Cluster binaries to
directories other than
<code class="filename">
C:\mysql\bin
</code>
;
however, if you do so, you must modify the paths shown in this
procedure accordingly. In particular, if the MySQL Server (SQL
node) binary is installed to a location other than
<code class="filename">
C:\mysql
</code>
or
<code class="filename">
C:\Program
Files\MySQL\MySQL Server 8.4
</code>
, or if the
SQL node's data directory is in a location other than
<code class="filename">
C:\mysql\data
</code>
or
<code class="filename">
C:\Program
Files\MySQL\MySQL Server 8.4\data
</code>
, extra
configuration options must be used on the command line or added
to the
<code class="filename">
my.ini
</code>
or
<code class="filename">
my.cnf
</code>
file when starting the SQL node. For
more information about configuring a MySQL Server to run in a
nonstandard location, see
<a class="xref" href="windows-install-archive.html" title="2.3.3 Configuration: Manually">
Section 2.3.3, “Configuration: Manually”
</a>
.
</p>
<p>
For a MySQL Server with NDB Cluster support to run as part of an
NDB Cluster, it must be started with the options
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndbcluster">
<code class="option">
--ndbcluster
</code>
</a>
and
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-connectstring">
<code class="option">
--ndb-connectstring
</code>
</a>
. While you
can specify these options on the command line, it is usually
more convenient to place them in an option file. To do this,
create a new text file in Notepad or another text editor. Enter
the following configuration information into this file:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa55344248"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token comment" spellcheck="true"># Options for mysqld process:</span>
ndbcluster <span class="token comment" spellcheck="true"># run NDB storage engine</span>
<span class="token constant">ndb-connectstring</span><span class="token attr-value"><span class="token punctuation">=</span>198.51.100.10 </span><span class="token comment" spellcheck="true"># location of management server</span></code></pre>
</div>
<p>
You can add other options used by this MySQL Server if desired
(see
<a class="xref" href="windows-create-option-file.html" title="2.3.3.2 Creating an Option File">
Section 2.3.3.2, “Creating an Option File”
</a>
), but the file
must contain the options shown, at a minimum. Save this file as
<code class="filename">
C:\mysql\my.ini
</code>
. This completes the
installation and setup for the SQL node.
</p>
<p>
<b>
Data nodes.
</b>
An NDB Cluster data node on a Windows host requires only a
single executable, one of either
<a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon">
<span class="command">
<strong>
ndbd.exe
</strong>
</span>
</a>
or
<a class="link" href="mysql-cluster-programs-ndbmtd.html" title="25.5.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)">
<span class="command">
<strong>
ndbmtd.exe
</strong>
</span>
</a>
. For this example, we assume
that you are using
<a class="link" href="mysql-cluster-programs-ndbd.html" title="25.5.1 ndbd — The NDB Cluster Data Node Daemon">
<span class="command">
<strong>
ndbd.exe
</strong>
</span>
</a>
, but the same
instructions apply when using
<a class="link" href="mysql-cluster-programs-ndbmtd.html" title="25.5.3 ndbmtd — The NDB Cluster Data Node Daemon (Multi-Threaded)">
<span class="command">
<strong>
ndbmtd.exe
</strong>
</span>
</a>
.
On each computer where you wish to run a data node (the
computers having the IP addresses 198.51.100.30 and
198.51.100.40), create the directories
<code class="filename">
C:\mysql
</code>
,
<code class="filename">
C:\mysql\bin
</code>
, and
<code class="filename">
C:\mysql\cluster-data
</code>
; then, on the
computer where you downloaded and extracted the
<code class="literal">
no-install
</code>
archive, locate
<code class="filename">
ndbd.exe
</code>
in the
<code class="filename">
C:\mysql\bin
</code>
directory. Copy this file to
the
<code class="filename">
C:\mysql\bin
</code>
directory on each of the
two data node hosts.
</p>
<p>
To function as part of an NDB Cluster, each data node must be
given the address or hostname of the management server. You can
supply this information on the command line using the
<a class="link" href="mysql-cluster-programs-ndb-config.html#option_ndb_config_ndb-connectstring">
<code class="option">
--ndb-connectstring
</code>
</a>
or
<code class="option">
-c
</code>
option when starting each data node process.
However, it is usually preferable to put this information in an
option file. To do this, create a new text file in Notepad or
another text editor and enter the following text:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa23994140"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysql_cluster]</span>
<span class="token comment" spellcheck="true"># Options for data node process:</span>
<span class="token constant">ndb-connectstring</span><span class="token attr-value"><span class="token punctuation">=</span>198.51.100.10 </span><span class="token comment" spellcheck="true"># location of management server</span></code></pre>
</div>
<p>
Save this file as
<code class="filename">
C:\mysql\my.ini
</code>
on the
data node host. Create another text file containing the same
information and save it on as
<code class="filename">
C:mysql\my.ini
</code>
on the other data node host,
or copy the my.ini file from the first data node host to the
second one, making sure to place the copy in the second data
node's
<code class="filename">
C:\mysql
</code>
directory. Both data
node hosts are now ready to be used in the NDB Cluster, which
leaves only the management node to be installed and configured.
</p>
<p>
<b>
Management node.
</b>
The only executable program required on a computer used for
hosting an NDB Cluster management node is the management
server program
<a class="link" href="mysql-cluster-programs-ndb-mgmd.html" title="25.5.4 ndb_mgmd — The NDB Cluster Management Server Daemon">
<span class="command">
<strong>
ndb_mgmd.exe
</strong>
</span>
</a>
. However, in
order to administer the NDB Cluster once it has been started,
you should also install the NDB Cluster management client
program
<a class="link" href="mysql-cluster-programs-ndb-mgm.html" title="25.5.5 ndb_mgm — The NDB Cluster Management Client">
<span class="command">
<strong>
ndb_mgm.exe
</strong>
</span>
</a>
on the same machine as
the management server. Locate these two programs on the
machine where you downloaded and extracted the
<code class="literal">
no-install
</code>
archive; this should be the
directory
<code class="filename">
C:\mysql\bin
</code>
on the SQL node
host. Create the directory
<code class="filename">
C:\mysql\bin
</code>
on the computer having the IP address 198.51.100.10, then copy
both programs to this directory.
</p>
<p>
You should now create two configuration files for use by
<code class="filename">
ndb_mgmd.exe
</code>
:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
A local configuration file to supply configuration data
specific to the management node itself. Typically, this file
needs only to supply the location of the NDB Cluster global
configuration file (see item 2).
</p>
<p>
To create this file, start a new text file in Notepad or
another text editor, and enter the following information:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa48438070"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysql_cluster]</span>
<span class="token comment" spellcheck="true"># Options for management node process</span>
<span class="token constant">config-file</span><span class="token attr-value"><span class="token punctuation">=</span>C:/mysql/bin/config.ini</span></code></pre>
</div>
<p>
Save this file as the text file
<code class="filename">
C:\mysql\bin\my.ini
</code>
.
</p>
</li>
<li class="listitem">
<p>
A global configuration file from which the management node
can obtain configuration information governing the NDB
Cluster as a whole. At a minimum, this file must contain a
section for each node in the NDB Cluster, and the IP
addresses or hostnames for the management node and all data
nodes (
<code class="literal">
HostName
</code>
configuration parameter).
It is also advisable to include the following additional
information:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The IP address or hostname of any SQL nodes
</p>
</li>
<li class="listitem">
<p>
The data memory and index memory allocated to each data
node (
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-datamemory">
<code class="literal">
DataMemory
</code>
</a>
and
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-indexmemory">
<code class="literal">
IndexMemory
</code>
</a>
configuration parameters)
</p>
</li>
<li class="listitem">
<p>
The number of fragment replicas, using the
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-noofreplicas">
<code class="literal">
NoOfReplicas
</code>
</a>
configuration parameter (see
<a class="xref" href="mysql-cluster-nodes-groups.html" title="25.2.2 NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions">
Section 25.2.2, “NDB Cluster Nodes, Node Groups, Fragment Replicas, and Partitions”
</a>
)
</p>
</li>
<li class="listitem">
<p>
The directory where each data node stores it data and
log file, and the directory where the management node
keeps its log files (in both cases, the
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-datadir">
<code class="literal">
DataDir
</code>
</a>
configuration parameter)
</p>
</li>
</ul>
</div>
<p>
Create a new text file using a text editor such as Notepad,
and input the following information:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa21813041"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[ndbd default]</span>
<span class="token comment" spellcheck="true"># Options affecting ndbd processes on all data nodes:</span>
<span class="token constant">NoOfReplicas</span><span class="token attr-value"><span class="token punctuation">=</span>2 </span><span class="token comment" spellcheck="true"># Number of fragment replicas</span>
<span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span>C:/mysql/cluster-data </span><span class="token comment" spellcheck="true"># Directory for each data node's data files</span>
<span class="token comment" spellcheck="true"> # Forward slashes used in directory path,</span>
<span class="token comment" spellcheck="true"> # rather than backslashes. This is correct;</span>
<span class="token comment" spellcheck="true"> # see Important note in text</span>
<span class="token constant">DataMemory</span><span class="token attr-value"><span class="token punctuation">=</span>80M </span><span class="token comment" spellcheck="true"># Memory allocated to data storage</span>
<span class="token constant">IndexMemory</span><span class="token attr-value"><span class="token punctuation">=</span>18M </span><span class="token comment" spellcheck="true"># Memory allocated to index storage</span>
<span class="token comment" spellcheck="true"> # For DataMemory and IndexMemory, we have used the</span>
<span class="token comment" spellcheck="true"> # default values. Since the "world" database takes up</span>
<span class="token comment" spellcheck="true"> # only about 500KB, this should be more than enough for</span>
<span class="token comment" spellcheck="true"> # this example Cluster setup.</span>
<span class="token selector">[ndb_mgmd]</span>
<span class="token comment" spellcheck="true"># Management process options:</span>
<span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span>198.51.100.10 </span><span class="token comment" spellcheck="true"># Hostname or IP address of management node</span>
<span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span>C:/mysql/bin/cluster-logs </span><span class="token comment" spellcheck="true"># Directory for management node log files</span>
<span class="token selector">[ndbd]</span>
<span class="token comment" spellcheck="true"># Options for data node "A":</span>
<span class="token comment" spellcheck="true"> # (one [ndbd] section per data node)</span>
<span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span>198.51.100.30 </span><span class="token comment" spellcheck="true"># Hostname or IP address</span>
<span class="token selector">[ndbd]</span>
<span class="token comment" spellcheck="true"># Options for data node "B":</span>
<span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span>198.51.100.40 </span><span class="token comment" spellcheck="true"># Hostname or IP address</span>
<span class="token selector">[mysqld]</span>
<span class="token comment" spellcheck="true"># SQL node options:</span>
<span class="token constant">HostName</span><span class="token attr-value"><span class="token punctuation">=</span>198.51.100.20 </span><span class="token comment" spellcheck="true"># Hostname or IP address</span></code></pre>
</div>
<p>
Save this file as the text file
<code class="filename">
C:\mysql\bin\config.ini
</code>
.
</p>
</li>
</ol>
</div>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
A single backslash character (
<code class="literal">
\
</code>
) cannot be
used when specifying directory paths in program options or
configuration files used by NDB Cluster on Windows. Instead,
you must either escape each backslash character with a second
backslash (
<code class="literal">
\\
</code>
), or replace the backslash
with a forward slash character (
<code class="literal">
/
</code>
). For
example, the following line from the
<code class="literal">
[ndb_mgmd]
</code>
section of an NDB Cluster
<code class="filename">
config.ini
</code>
file does not work:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-ini"><div class="docs-select-all right" id="sa94433102"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span>C:\mysql\bin\cluster-logs</span></code></pre>
</div>
<p>
Instead, you may use either of the following:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-ini"><div class="docs-select-all right" id="sa12508582"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span>C:\\mysql\\bin\\cluster-logs </span><span class="token comment" spellcheck="true"># Escaped backslashes</span></code></pre>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-ini"><div class="docs-select-all right" id="sa88477257"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token constant">DataDir</span><span class="token attr-value"><span class="token punctuation">=</span>C:/mysql/bin/cluster-logs </span><span class="token comment" spellcheck="true"># Forward slashes</span></code></pre>
</div>
<p>
For reasons of brevity and legibility, we recommend that you
use forward slashes in directory paths used in NDB Cluster
program options and configuration files on Windows.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-features-temptables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-features-temptables">
</a>
19.5.1.31 Replication and Temporary Tables
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045135125184">
</a>
<a class="indexterm" name="idm46045135123696">
</a>
<a class="indexterm" name="idm46045135122208">
</a>
<p>
In MySQL 8.4, when
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
is set to
<code class="literal">
ROW
</code>
or
<code class="literal">
MIXED
</code>
, statements
that exclusively use temporary tables are not logged on the
source, and therefore the temporary tables are not replicated.
Statements that involve a mix of temporary and nontemporary
tables are logged on the source only for the operations on
nontemporary tables, and the operations on temporary tables are
not logged. This means that there are never any temporary tables
on the replica to be lost in the event of an unplanned shutdown
by the replica. For more information about row-based replication
and temporary tables, see
<a class="xref" href="replication-rbr-usage.html#replication-rbr-usage-temptables" title="Row-based logging of temporary tables">
Row-based logging of temporary tables
</a>
.
</p>
<p>
When
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
is set to
<code class="literal">
STATEMENT
</code>
, operations on temporary tables are
logged on the source and replicated on the replica, provided
that the statements involving temporary tables can be logged
safely using statement-based format. In this situation, loss of
replicated temporary tables on the replica can be an issue. In
statement-based replication mode,
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TEMPORARY
TABLE
</code>
</a>
and
<a class="link" href="drop-table.html" title="15.1.32 DROP TABLE Statement">
<code class="literal">
DROP TEMPORARY
TABLE
</code>
</a>
statements cannot be used inside a transaction,
procedure, function, or trigger when GTIDs are in use on the
server (that is, when the
<a class="link" href="replication-options-gtids.html#sysvar_enforce_gtid_consistency">
<code class="literal">
enforce_gtid_consistency
</code>
</a>
system
variable is set to
<code class="literal">
ON
</code>
). They can be used
outside these contexts when GTIDs are in use, provided that
<a class="link" href="server-system-variables.html#sysvar_autocommit">
<code class="literal">
autocommit=1
</code>
</a>
is set.
</p>
<p>
Because of the differences in behavior between row-based or
mixed replication mode and statement-based replication mode
regarding temporary tables, you cannot switch the replication
format at runtime, if the change applies to a context (global or
session) that contains any open temporary tables. For more
details, see the description of the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
option.
</p>
<p>
<b>
Safe replica shutdown when using temporary tables.
</b>
In statement-based replication mode, temporary tables are
replicated except in the case where you stop the replica
server (not just the replication threads) and you have
replicated temporary tables that are open for use in updates
that have not yet been executed on the replica. If you stop
the replica server, the temporary tables needed by those
updates are no longer available when the replica is restarted.
To avoid this problem, do not shut down the replica while it
has temporary tables open. Instead, use the following
procedure:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Issue a
<code class="literal">
STOP REPLICA
SQL_THREAD
</code>
statement.
</p>
</li>
<li class="listitem">
<p>
Use
<a class="link" href="show-status.html" title="15.7.7.37 SHOW STATUS Statement">
<code class="literal">
SHOW STATUS
</code>
</a>
to check the
value of the
<a class="link" href="server-status-variables.html#statvar_Replica_open_temp_tables">
<code class="literal">
Replica_open_temp_tables
</code>
</a>
status variable.
</p>
</li>
<li class="listitem">
<p>
If the value is not 0, restart the replication SQL thread
with
<code class="literal">
START REPLICA
SQL_THREAD
</code>
and repeat the procedure later.
</p>
</li>
<li class="listitem">
<p>
When the value is 0, issue a
<a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program">
<span class="command">
<strong>
mysqladmin
shutdown
</strong>
</span>
</a>
command to stop the replica.
</p>
</li>
</ol>
</div>
<p>
<b>
Temporary tables and replication options.
</b>
By default, with statement-based replication, all temporary
tables are replicated; this happens whether or not there are
any matching
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-db">
<code class="option">
--replicate-do-db
</code>
</a>
,
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-table">
<code class="option">
--replicate-do-table
</code>
</a>
, or
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-wild-do-table">
<code class="option">
--replicate-wild-do-table
</code>
</a>
options in effect. However, the
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-ignore-table">
<code class="option">
--replicate-ignore-table
</code>
</a>
and
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-wild-ignore-table">
<code class="option">
--replicate-wild-ignore-table
</code>
</a>
options are honored for temporary tables. The exception is
that to enable correct removal of temporary tables at the end
of a session, a replica always replicates a
<code class="literal">
DROP
TEMPORARY TABLE IF EXISTS
</code>
statement, regardless of
any exclusion rules that would normally apply for the
specified table.
</p>
<p>
A recommended practice when using statement-based replication is
to designate a prefix for exclusive use in naming temporary
tables that you do not want replicated, then employ a
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-wild-ignore-table">
<code class="option">
--replicate-wild-ignore-table
</code>
</a>
option to match that prefix. For example, you might give all
such tables names beginning with
<code class="literal">
norep
</code>
(such
as
<code class="literal">
norepmytable
</code>
,
<code class="literal">
norepyourtable
</code>
, and so on), then use
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-wild-ignore-table">
<code class="option">
--replicate-wild-ignore-table=norep%
</code>
</a>
to prevent them from being replicated.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-oci-marketplace-connecting.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="mysql-oci-marketplace-connecting">
</a>
34.4 Connecting
</h2>
</div>
</div>
</div>
<p>
This section describes the various connection methods for
connecting to the deployed MySQL server on the OCI Compute
Instance.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="mysql-oci-marketplace-connecting-ssh">
</a>
Connecting with SSH
</h3>
</div>
</div>
</div>
<p>
This section gives some detail on connecting from a UNIX-like
platform to the OCI Compute. For more information on connecting
with SSH, see
<a class="ulink" href="https://docs.oracle.com/en/cloud/iaas/compute-iaas-cloud/stcsg/accessing-oracle-linux-instance-using-ssh.html#GUID-D947E2CC-0D4C-43F4-B2A9-A517037D6C11" target="_blank">
Accessing
an Oracle Linux Instance Using SSH
</a>
and
<a class="ulink" href="https://docs.cloud.oracle.com/iaas/Content/GSG/Tasks/testingconnection.htm" target="_blank">
Connecting
to Your Instance
</a>
.
</p>
<p>
To connect to the Oracle Linux running on the Compute Instance
with SSH, run the following command:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa82733816"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">ssh opc@<em class="replaceable">computeIP</em></code></pre>
</div>
<p>
where
<code class="literal">
opc
</code>
is the compute user and
<em class="replaceable">
<code>
computeIP
</code>
</em>
is the IP address of your
Compute Instance.
</p>
<p>
To find the temporary root password created for the root user,
run the following command:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa5254481"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">sudo grep <span class="token atrule">'temporary password'</span> /var/log/mysqld<span class="token punctuation">.</span>log</code></pre>
</div>
<p>
To change your default password, log in to the server using the
generated, temporary password, using the following command:
<code class="literal">
mysql -uroot -p
</code>
. Then run the following:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa37994823"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">USER</span> <span class="token string">'root'</span>@<span class="token string">'localhost'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'MyNewPass4!'</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="mysql-oci-marketplace-connecting-mysqlclient">
</a>
Connecting with MySQL Client
</h3>
</div>
</div>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
To connect from your local MySQL client, you must first create
on the MySQL server a user which allows remote login.
</p>
</div>
<p>
To connect to the MySQL Server from your local MySQL client, run
the following command from your shell session:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa30912652"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">mysql <span class="token operator">-</span>uroot <span class="token operator">-</span>p <span class="token operator">-</span>h<em class="replaceable">computeIP</em></code></pre>
</div>
<p>
where
<em class="replaceable">
<code>
computeIP
</code>
</em>
is the IP address of
your Compute Instance.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="mysql-oci-marketplace-connecting-mysqlshell">
</a>
Connecting with MySQL Shell
</h3>
</div>
</div>
</div>
<p>
To connect to the MySQL Server from your local MySQL Shell, run
the following command to start your shell session:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa34165496"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqlsh root@<em class="replaceable">computeIP</em></code></pre>
</div>
<p>
where
<em class="replaceable">
<code>
computeIP
</code>
</em>
is the IP address of
your Compute Instance.
</p>
<p>
For more information on MySQL Shell connections, see
<a class="ulink" href="/doc/mysql-shell/8.4/en/mysql-shell-connections.html" target="_top">
MySQL Shell Connections
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="mysql-oci-marketplace-connecting-workbench">
</a>
Connecting with Workbench
</h3>
</div>
</div>
</div>
<p>
To connect to the MySQL Server from MySQL Workbench, see
<a class="ulink" href="/doc/workbench/en/wb-mysql-connections.html" target="_top">
Connections in MySQL Workbench
</a>
.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/silent-column-changes.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="silent-column-changes">
</a>
15.1.20.7 Silent Column Specification Changes
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045184842560">
</a>
<p>
In some cases, MySQL silently changes column specifications from
those given in a
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
or
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
statement. These
might be changes to a data type, to attributes associated with a
data type, or to an index specification.
</p>
<p>
All changes are subject to the internal row-size limit of 65,535
bytes, which may cause some attempts at data type changes to
fail. See
<a class="xref" href="column-count-limit.html" title="10.4.7 Limits on Table Column Count and Row Size">
Section 10.4.7, “Limits on Table Column Count and Row Size”
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Columns that are part of a
<code class="literal">
PRIMARY KEY
</code>
are made
<code class="literal">
NOT NULL
</code>
even if not declared
that way.
</p>
</li>
<li class="listitem">
<p>
Trailing spaces are automatically deleted from
<a class="link" href="enum.html" title="13.3.5 The ENUM Type">
<code class="literal">
ENUM
</code>
</a>
and
<a class="link" href="set.html" title="13.3.6 The SET Type">
<code class="literal">
SET
</code>
</a>
member values when the
table is created.
</p>
</li>
<li class="listitem">
<p>
MySQL maps certain data types used by other SQL database
vendors to MySQL types. See
<a class="xref" href="other-vendor-data-types.html" title="13.9 Using Data Types from Other Database Engines">
Section 13.9, “Using Data Types from Other Database Engines”
</a>
.
</p>
</li>
<li class="listitem">
<p>
If you include a
<code class="literal">
USING
</code>
clause to specify
an index type that is not permitted for a given storage
engine, but there is another index type available that the
engine can use without affecting query results, the engine
uses the available type.
</p>
</li>
<li class="listitem">
<p>
If strict SQL mode is not enabled, a
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
column with a length
specification greater than 65535 is converted to
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
, and a
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
VARBINARY
</code>
</a>
column with a
length specification greater than 65535 is converted to
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
. Otherwise, an error
occurs in either of these cases.
</p>
</li>
<li class="listitem">
<p>
Specifying the
<code class="literal">
CHARACTER SET binary
</code>
attribute for a character data type causes the column to be
created as the corresponding binary data type:
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
becomes
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
BINARY
</code>
</a>
,
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
becomes
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
VARBINARY
</code>
</a>
, and
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
becomes
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
. For the
<a class="link" href="enum.html" title="13.3.5 The ENUM Type">
<code class="literal">
ENUM
</code>
</a>
and
<a class="link" href="set.html" title="13.3.6 The SET Type">
<code class="literal">
SET
</code>
</a>
data types, this does not
occur; they are created as declared. Suppose that you
specify a table using this definition:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa72594072"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t
<span class="token punctuation">(</span>
c1 <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <span class="token datatype">binary</span><span class="token punctuation">,</span>
c2 <span class="token datatype">TEXT</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <span class="token datatype">binary</span><span class="token punctuation">,</span>
c3 <span class="token datatype">ENUM</span><span class="token punctuation">(</span><span class="token string">'a'</span><span class="token punctuation">,</span><span class="token string">'b'</span><span class="token punctuation">,</span><span class="token string">'c'</span><span class="token punctuation">)</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <span class="token datatype">binary</span>
<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The resulting table has this definition:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa2759581"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t
<span class="token punctuation">(</span>
c1 <span class="token datatype">VARBINARY</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
c2 <span class="token datatype">BLOB</span><span class="token punctuation">,</span>
c3 <span class="token datatype">ENUM</span><span class="token punctuation">(</span><span class="token string">'a'</span><span class="token punctuation">,</span><span class="token string">'b'</span><span class="token punctuation">,</span><span class="token string">'c'</span><span class="token punctuation">)</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <span class="token datatype">binary</span>
<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
To see whether MySQL used a data type other than the one you
specified, issue a
<a class="link" href="describe.html" title="15.8.1 DESCRIBE Statement">
<code class="literal">
DESCRIBE
</code>
</a>
or
<a class="link" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement">
<code class="literal">
SHOW CREATE TABLE
</code>
</a>
statement after
creating or altering the table.
</p>
<a class="indexterm" name="idm46045184804576">
</a>
<p>
Certain other data type changes can occur if you compress a
table using
<a class="link" href="myisampack.html" title="6.6.6 myisampack — Generate Compressed, Read-Only MyISAM Tables">
<span class="command">
<strong>
myisampack
</strong>
</span>
</a>
. See
<a class="xref" href="compressed-format.html" title="18.2.3.3 Compressed Table Characteristics">
Section 18.2.3.3, “Compressed Table Characteristics”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/show-binary-log-status.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="show-binary-log-status">
</a>
15.7.7.1 SHOW BINARY LOG STATUS Statement
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045171215856">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa22756206"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SHOW</span> <span class="token datatype">BINARY</span> LOG <span class="token keyword">STATUS</span></code></pre>
</div>
<p>
This statement provides status information about binary log
files on the source server, and requires the
<a class="link" href="privileges-provided.html#priv_replication-client">
<code class="literal">
REPLICATION CLIENT
</code>
</a>
privilege (or
the deprecated
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege).
</p>
<p>
Example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa27604714"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token datatype">BINARY</span> LOG <span class="token keyword">STATUS</span>\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
File<span class="token punctuation">:</span> source-bin.000002
Position<span class="token punctuation">:</span> 1307
Binlog_Do_DB<span class="token punctuation">:</span> test
Binlog_Ignore_DB<span class="token punctuation">:</span> manual, mysql
Executed_Gtid_Set<span class="token punctuation">:</span> 3E11FA47-71CA-11E1-9E33-C80AA9429562<span class="token punctuation">:</span>1-5
</span><span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
When global transaction IDs are in use,
<code class="literal">
Executed_Gtid_Set
</code>
shows the set of GTIDs for
transactions that have been executed on the source. This is the
same as the value for the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
system variable
on this server, as well as the value for
<code class="literal">
Executed_Gtid_Set
</code>
in the output of
<a class="link" href="show-replica-status.html" title="15.7.7.35 SHOW REPLICA STATUS Statement">
<code class="literal">
SHOW REPLICA STATUS
</code>
</a>
on this
server.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-features-memory.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-features-memory">
</a>
19.5.1.21 Replication and MEMORY Tables
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045135331520">
</a>
<a class="indexterm" name="idm46045135330032">
</a>
<p>
When a replication source server shuts down and restarts, its
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables become empty. To
replicate this effect to replicas, the first time that the
source uses a given
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
table
after startup, it logs an event that notifies replicas that the
table must be emptied by writing a
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
or
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
statement for that
table to the binary log. This generated event is identifiable by
a comment in the binary log, and if GTIDs are in use on the
server, it has a GTID assigned. The statement is always logged
in statement format, even if the binary logging format is set to
<code class="literal">
ROW
</code>
, and it is written even if
<code class="literal">
read_only
</code>
or
<code class="literal">
super_read_only
</code>
mode is set on the server.
Note that the replica still has outdated data in a
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
table during the interval
between the source's restart and its first use of the table. To
avoid this interval when a direct query to the replica could
return stale data, you can set the
<a class="link" href="server-system-variables.html#sysvar_init_file">
<code class="literal">
init_file
</code>
</a>
system variable to
name a file containing statements that populate the
<code class="literal">
MEMORY
</code>
table on the source at startup.
</p>
<p>
When a replica server shuts down and restarts, its
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables become empty. This
causes the replica to be out of synchrony with the source and
may lead to other failures or cause the replica to stop:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Row-format updates and deletes received from the source may
fail with
<code class="literal">
Can't find record in
'
<em class="replaceable">
<code>
memory_table
</code>
</em>
'
</code>
.
</p>
</li>
<li class="listitem">
<p>
Statements such as
<a class="link" href="insert-select.html" title="15.2.7.1 INSERT ... SELECT Statement">
<code class="literal">
INSERT INTO
... SELECT FROM
<em class="replaceable">
<code>
memory_table
</code>
</em>
</code>
</a>
may insert
a different set of rows on the source and replica.
</p>
</li>
</ul>
</div>
<p>
The replica also writes a
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
or
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
statement to
its own binary log, which is passed on to any downstream
replicas, causing them to empty their own
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables.
</p>
<p>
The safe way to restart a replica that is replicating
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables is to first drop or
delete all rows from the
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables on the source and wait until those changes have
replicated to the replica. Then it is safe to restart the
replica.
</p>
<p>
An alternative restart method may apply in some cases. When
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=ROW
</code>
</a>
, you can
prevent the replica from stopping if you set
<a class="link" href="replication-options-replica.html#sysvar_replica_exec_mode">
<code class="literal">
replica_exec_mode=IDEMPOTENT
</code>
</a>
before you start the replica again. This allows the replica to
continue to replicate, but its
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables still differ from
those on the source. This is acceptable if the application logic
is such that the contents of
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables can be safely lost (for example, if the
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables are used for
caching).
<a class="link" href="replication-options-replica.html#sysvar_replica_exec_mode">
<code class="literal">
replica_exec_mode=IDEMPOTENT
</code>
</a>
applies globally to all tables, so it may hide other replication
errors in non-
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables.
</p>
<p>
(The method just described is not applicable in NDB Cluster,
where
<a class="link" href="replication-options-replica.html#sysvar_replica_exec_mode">
<code class="literal">
replica_exec_mode
</code>
</a>
is
always
<code class="literal">
IDEMPOTENT
</code>
, and cannot be changed.)
</p>
<p>
The size of
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables is
limited by the value of the
<a class="link" href="server-system-variables.html#sysvar_max_heap_table_size">
<code class="literal">
max_heap_table_size
</code>
</a>
system
variable, which is not replicated (see
<a class="xref" href="replication-features-variables.html" title="19.5.1.39 Replication and Variables">
Section 19.5.1.39, “Replication and Variables”
</a>
). A change in
<code class="literal">
max_heap_table_size
</code>
takes effect for
<code class="literal">
MEMORY
</code>
tables that are created or updated
using
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
... ENGINE = MEMORY
</code>
</a>
or
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE
TABLE
</code>
</a>
following the change, or for all
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables following a server
restart. If you increase the value of this variable on the
source without doing so on the replica, it becomes possible for
a table on the source to grow larger than its counterpart on the
replica, leading to inserts that succeed on the source but fail
on the replica with
<span class="errortext">
Table is full
</span>
errors.
This is a known issue (Bug #48666). In such cases, you must set
the global value of
<a class="link" href="server-system-variables.html#sysvar_max_heap_table_size">
<code class="literal">
max_heap_table_size
</code>
</a>
on the
replica as well as on the source, then restart replication. It
is also recommended that you restart both the source and replica
MySQL servers, to ensure that the new value takes complete
(global) effect on each of them.
</p>
<p>
See
<a class="xref" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
Section 18.3, “The MEMORY Storage Engine”
</a>
, for more
information about
<a class="link" href="memory-storage-engine.html" title="18.3 The MEMORY Storage Engine">
<code class="literal">
MEMORY
</code>
</a>
tables.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-monitoring.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="group-replication-monitoring">
</a>
20.4 Monitoring Group Replication
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="group-replication-gtids.html">
20.4.1 GTIDs and Group Replication
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-server-states.html">
20.4.2 Group Replication Server States
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-replication-group-members.html">
20.4.3 The replication_group_members Table
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-replication-group-member-stats.html">
20.4.4 The replication_group_member_stats Table
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045133752064">
</a>
<p>
You can use the MySQL
<a class="link" href="performance-schema.html" title="Chapter 29 MySQL Performance Schema">
Performance
Schema
</a>
to monitor Group Replication. These Performance Schema
tables display information specific to Group Replication:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="performance-schema-replication-group-member-stats-table.html" title="29.12.11.15 The replication_group_member_stats Table">
<code class="literal">
replication_group_member_stats
</code>
</a>
: See
<a class="xref" href="group-replication-replication-group-member-stats.html" title="20.4.4 The replication_group_member_stats Table">
Section 20.4.4, “The replication_group_member_stats Table”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-replication-group-members-table.html" title="29.12.11.16 The replication_group_members Table">
<code class="literal">
replication_group_members
</code>
</a>
: See
<a class="xref" href="group-replication-replication-group-members.html" title="20.4.3 The replication_group_members Table">
Section 20.4.3, “The replication_group_members Table”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-replication-group-communication-information-table.html" title="29.12.11.10 The replication_group_communication_information Table">
<code class="literal">
replication_group_communication_information
</code>
</a>
:
See
<a class="xref" href="performance-schema-replication-group-communication-information-table.html" title="29.12.11.10 The replication_group_communication_information Table">
Section 29.12.11.10, “The replication_group_communication_information Table”
</a>
.
</p>
</li>
</ul>
</div>
<p>
These Performance Schema replication tables also show information
relating to Group Replication:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="performance-schema-replication-connection-status-table.html" title="29.12.11.13 The replication_connection_status Table">
<code class="literal">
replication_connection_status
</code>
</a>
shows
information regarding Group Replication, such as transactions
received from the group and queued in the applier queue (relay
log).
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-replication-applier-status-table.html" title="29.12.11.5 The replication_applier_status Table">
<code class="literal">
replication_applier_status
</code>
</a>
shows
the states of channels and threads relating to Group
Replication. These can also be used to monitor what individual
worker threads are doing.
</p>
</li>
</ul>
</div>
<p>
Replication channels created by the Group Replication plugin are
listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
group_replication_recovery
</code>
: Used for
replication changes related to distributed recovery.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
group_replication_applier
</code>
: Used for the
incoming changes from the group, to apply transactions coming
directly from the group.
</p>
</li>
</ul>
</div>
<p>
For information about system variables affecting Group Replication,
see
<a class="xref" href="group-replication-system-variables.html" title="20.9.1 Group Replication System Variables">
Section 20.9.1, “Group Replication System Variables”
</a>
. See
<a class="xref" href="group-replication-status-variables.html" title="20.9.2 Group Replication Status Variables">
Section 20.9.2, “Group Replication Status Variables”
</a>
, for status
variables providing information about Group Replication.
</p>
<p>
Messages relating to Group Replication lifecycle events other than
errors are classified as system messages; these are always written
to the replication group member' error log. You can use this
information to review the history of a given server's
membership in a replication group.
</p>
<p>
Some lifecycle events that affect the whole group are logged on
every group member, such as a new member entering
<code class="literal">
ONLINE
</code>
status in the group or a primary election.
Other events are logged only on the member where they take place,
such as super read only mode being enabled or disabled on the
member, or the member leaving the group. A number of lifecycle
events that can indicate an issue if they occur frequently are
logged as warning messages, including a member becoming unreachable
and then reachable again, and a member starting distributed recovery
by state transfer from the binary log or by a remote cloning
operation.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If you are monitoring one or more secondary instances using
<a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program">
<span class="command">
<strong>
mysqladmin
</strong>
</span>
</a>
, you should be aware that a
<a class="link" href="flush.html#flush-status">
<code class="literal">
FLUSH STATUS
</code>
</a>
statement executed by
this utility creates a GTID event on the local instance which may
impact future group operations.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-option-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-option-tables">
</a>
25.4.2.5 NDB Cluster mysqld Option and Variable Reference
</h4>
</div>
</div>
</div>
<p>
The following list includes command-line options, system
variables, and status variables applicable within
<code class="literal">
mysqld
</code>
when it is running as an SQL node in
an NDB Cluster. For a reference to
<span class="emphasis">
<em>
all
</em>
</span>
command-line options, system variables, and status variables
used with or relating to
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
, see
<a class="xref" href="server-option-variable-reference.html" title="7.1.4 Server Option, System Variable, and Status Variable Reference">
Section 7.1.4, “Server Option, System Variable, and Status Variable Reference”
</a>
.
</p>
<div class="itemizedlist">
<a name="mysql-cluster-mysqld-optvars-summary-list">
</a>
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="server-status-variables.html#statvar_Com_xxx">
Com_show_ndb_status
</a>
</code>
:
Count of SHOW NDB STATUS statements.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Handler_discover">
Handler_discover
</a>
</code>
:
Number of times that tables have been discovered.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-applier-allow-skip-epoch">
ndb-applier-allow-skip-epoch
</a>
</code>
:
Lets replication applier skip epochs.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-batch-size">
ndb-batch-size
</a>
</code>
:
Size (in bytes) to use for NDB transaction batches.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-blob-read-batch-bytes">
ndb-blob-read-batch-bytes
</a>
</code>
:
Specifies size in bytes that large BLOB reads should be
batched into. 0 = no limit.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-blob-write-batch-bytes">
ndb-blob-write-batch-bytes
</a>
</code>
:
Specifies size in bytes that large BLOB writes should be
batched into. 0 = no limit.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-cluster-connection-pool">
ndb-cluster-connection-pool
</a>
</code>
:
Number of connections to cluster used by MySQL.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-cluster-connection-pool-nodeids">
ndb-cluster-connection-pool-nodeids
</a>
</code>
:
Comma-separated list of node IDs for connections to cluster
used by MySQL; number of nodes in list must match value set
for --ndb-cluster-connection-pool.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-connectstring">
ndb-connectstring
</a>
</code>
:
Address of NDB management server distributing configuration
information for this cluster.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-default-column-format">
ndb-default-column-format
</a>
</code>
:
Use this value (FIXED or DYNAMIC) by default for
COLUMN_FORMAT and ROW_FORMAT options when creating or adding
table columns.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-deferred-constraints">
ndb-deferred-constraints
</a>
</code>
:
Specifies that constraint checks on unique indexes (where
these are supported) should be deferred until commit time.
Not normally needed or used; for testing purposes only.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-distribution">
ndb-distribution
</a>
</code>
:
Default distribution for new tables in NDBCLUSTER (KEYHASH
or LINHASH, default is KEYHASH).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-apply-status">
ndb-log-apply-status
</a>
</code>
:
Cause MySQL server acting as replica to log
mysql.ndb_apply_status updates received from its immediate
source in its own binary log, using its own server ID.
Effective only if server is started with --ndbcluster
option.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-empty-epochs">
ndb-log-empty-epochs
</a>
</code>
:
When enabled, causes epochs in which there were no changes
to be written to ndb_apply_status and ndb_binlog_index
tables, even when --log-slave-updates is enabled.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-empty-update">
ndb-log-empty-update
</a>
</code>
:
When enabled, causes updates that produced no changes to be
written to ndb_apply_status and ndb_binlog_index tables,
even when --log-slave-updates is enabled.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-exclusive-reads">
ndb-log-exclusive-reads
</a>
</code>
:
Log primary key reads with exclusive locks; allow conflict
resolution based on read conflicts.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-fail-terminate">
ndb-log-fail-terminate
</a>
</code>
:
Terminate mysqld process if complete logging of all found
row events is not possible.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-orig">
ndb-log-orig
</a>
</code>
:
Log originating server id and epoch in
mysql.ndb_binlog_index table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-transaction-dependency">
ndb-log-transaction-dependency
</a>
</code>
:
Make binary log thread calculate transaction dependencies
for every transaction it writes to binary log.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-transaction-id">
ndb-log-transaction-id
</a>
</code>
:
Write NDB transaction IDs in binary log. Requires
--log-bin-v1-events=OFF.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-minimal">
ndb-log-update-minimal
</a>
</code>
:
Log updates in minimal format.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-updated-only">
ndb-log-updated-only
</a>
</code>
:
Log updates only (ON) or complete rows (OFF).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-as-write">
ndb-log-update-as-write
</a>
</code>
:
Toggles logging of updates on source between updates (OFF)
and writes (ON).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-mgm-tls">
ndb-mgm-tls
</a>
</code>
:
Whether TLS connection requirements are strict or relaxed.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-mgmd-host">
ndb-mgmd-host
</a>
</code>
:
Set host (and port, if desired) for connecting to management
server.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-nodeid">
ndb-nodeid
</a>
</code>
:
NDB Cluster node ID for this MySQL server.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-optimized-node-selection">
ndb-optimized-node-selection
</a>
</code>
:
Enable optimizations for selection of nodes for
transactions. Enabled by default; use
--skip-ndb-optimized-node-selection to disable.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-tls-search-path">
ndb-tls-search-path
</a>
</code>
:
Directories to search for NDB TLS CAs and private keys.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-transid-mysql-connection-map">
ndb-transid-mysql-connection-map
</a>
</code>
:
Enable or disable ndb_transid_mysql_connection_map plugin;
that is, enable or disable INFORMATION_SCHEMA table having
that name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-wait-connected">
ndb-wait-connected
</a>
</code>
:
Time (in seconds) for MySQL server to wait for connection to
cluster management and data nodes before accepting MySQL
client connections.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-wait-setup">
ndb-wait-setup
</a>
</code>
:
Time (in seconds) for MySQL server to wait for NDB engine
setup to complete.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-allow-copying-alter-table">
ndb-allow-copying-alter-table
</a>
</code>
:
Set to OFF to keep ALTER TABLE from using copying operations
on NDB tables.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_deferred_count">
Ndb_api_adaptive_send_deferred_count
</a>
</code>
:
Number of adaptive send calls not actually sent by this
MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_deferred_count_session">
Ndb_api_adaptive_send_deferred_count_session
</a>
</code>
:
Number of adaptive send calls not actually sent in this
client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_deferred_count_replica">
Ndb_api_adaptive_send_deferred_count_replica
</a>
</code>
:
Number of adaptive send calls not actually sent by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_deferred_count_slave">
Ndb_api_adaptive_send_deferred_count_slave
</a>
</code>
:
Number of adaptive send calls not actually sent by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_forced_count">
Ndb_api_adaptive_send_forced_count
</a>
</code>
:
Number of adaptive sends with forced-send set sent by this
MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_forced_count_session">
Ndb_api_adaptive_send_forced_count_session
</a>
</code>
:
Number of adaptive sends with forced-send set in this client
session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_forced_count_replica">
Ndb_api_adaptive_send_forced_count_replica
</a>
</code>
:
Number of adaptive sends with forced-send set sent by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_forced_count_slave">
Ndb_api_adaptive_send_forced_count_slave
</a>
</code>
:
Number of adaptive sends with forced-send set sent by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_unforced_count">
Ndb_api_adaptive_send_unforced_count
</a>
</code>
:
Number of adaptive sends without forced-send sent by this
MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_unforced_count_session">
Ndb_api_adaptive_send_unforced_count_session
</a>
</code>
:
Number of adaptive sends without forced-send in this client
session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_unforced_count_replica">
Ndb_api_adaptive_send_unforced_count_replica
</a>
</code>
:
Number of adaptive sends without forced-send sent by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_adaptive_send_unforced_count_slave">
Ndb_api_adaptive_send_unforced_count_slave
</a>
</code>
:
Number of adaptive sends without forced-send sent by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_bytes_received_count">
Ndb_api_bytes_received_count
</a>
</code>
:
Quantity of data (in bytes) received from data nodes by this
MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_bytes_received_count_session">
Ndb_api_bytes_received_count_session
</a>
</code>
:
Quantity of data (in bytes) received from data nodes in this
client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_bytes_received_count_replica">
Ndb_api_bytes_received_count_replica
</a>
</code>
:
Quantity of data (in bytes) received from data nodes by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_bytes_received_count_slave">
Ndb_api_bytes_received_count_slave
</a>
</code>
:
Quantity of data (in bytes) received from data nodes by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_bytes_sent_count">
Ndb_api_bytes_sent_count
</a>
</code>
:
Quantity of data (in bytes) sent to data nodes by this MySQL
Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_bytes_sent_count_session">
Ndb_api_bytes_sent_count_session
</a>
</code>
:
Quantity of data (in bytes) sent to data nodes in this
client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_bytes_sent_count_replica">
Ndb_api_bytes_sent_count_replica
</a>
</code>
:
Qunatity of data (in bytes) sent to data nodes by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_bytes_sent_count_slave">
Ndb_api_bytes_sent_count_slave
</a>
</code>
:
Qunatity of data (in bytes) sent to data nodes by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_event_bytes_count">
Ndb_api_event_bytes_count
</a>
</code>
:
Number of bytes of events received by this MySQL Server (SQL
node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_event_bytes_count_injector">
Ndb_api_event_bytes_count_injector
</a>
</code>
:
Number of bytes of event data received by NDB binary log
injector thread.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_event_data_count">
Ndb_api_event_data_count
</a>
</code>
:
Number of row change events received by this MySQL Server
(SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_event_data_count_injector">
Ndb_api_event_data_count_injector
</a>
</code>
:
Number of row change events received by NDB binary log
injector thread.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_event_nondata_count">
Ndb_api_event_nondata_count
</a>
</code>
:
Number of events received, other than row change events, by
this MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_event_nondata_count_injector">
Ndb_api_event_nondata_count_injector
</a>
</code>
:
Number of events received, other than row change events, by
NDB binary log injector thread.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_pk_op_count">
Ndb_api_pk_op_count
</a>
</code>
:
Number of operations based on or using primary keys by this
MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_pk_op_count_session">
Ndb_api_pk_op_count_session
</a>
</code>
:
Number of operations based on or using primary keys in this
client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_pk_op_count_replica">
Ndb_api_pk_op_count_replica
</a>
</code>
:
Number of operations based on or using primary keys by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_pk_op_count_slave">
Ndb_api_pk_op_count_slave
</a>
</code>
:
Number of operations based on or using primary keys by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_pruned_scan_count">
Ndb_api_pruned_scan_count
</a>
</code>
:
Number of scans that have been pruned to one partition by
this MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_pruned_scan_count_session">
Ndb_api_pruned_scan_count_session
</a>
</code>
:
Number of scans that have been pruned to one partition in
this client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_pruned_scan_count_replica">
Ndb_api_pruned_scan_count_replica
</a>
</code>
:
Number of scans that have been pruned to one partition by
this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_pruned_scan_count_slave">
Ndb_api_pruned_scan_count_slave
</a>
</code>
:
Number of scans that have been pruned to one partition by
this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_range_scan_count">
Ndb_api_range_scan_count
</a>
</code>
:
Number of range scans that have been started by this MySQL
Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_range_scan_count_session">
Ndb_api_range_scan_count_session
</a>
</code>
:
Number of range scans that have been started in this client
session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_range_scan_count_replica">
Ndb_api_range_scan_count_replica
</a>
</code>
:
Number of range scans that have been started by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_range_scan_count_slave">
Ndb_api_range_scan_count_slave
</a>
</code>
:
Number of range scans that have been started by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_read_row_count">
Ndb_api_read_row_count
</a>
</code>
:
Total number of rows that have been read by this MySQL
Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_read_row_count_session">
Ndb_api_read_row_count_session
</a>
</code>
:
Total number of rows that have been read in this client
session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_read_row_count_replica">
Ndb_api_read_row_count_replica
</a>
</code>
:
Total number of rows that have been read by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_read_row_count_slave">
Ndb_api_read_row_count_slave
</a>
</code>
:
Total number of rows that have been read by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_scan_batch_count">
Ndb_api_scan_batch_count
</a>
</code>
:
Number of batches of rows received by this MySQL Server (SQL
node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_scan_batch_count_session">
Ndb_api_scan_batch_count_session
</a>
</code>
:
Number of batches of rows received in this client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_scan_batch_count_replica">
Ndb_api_scan_batch_count_replica
</a>
</code>
:
Number of batches of rows received by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_scan_batch_count_slave">
Ndb_api_scan_batch_count_slave
</a>
</code>
:
Number of batches of rows received by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_table_scan_count">
Ndb_api_table_scan_count
</a>
</code>
:
Number of table scans that have been started, including
scans of internal tables, by this MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_table_scan_count_session">
Ndb_api_table_scan_count_session
</a>
</code>
:
Number of table scans that have been started, including
scans of internal tables, in this client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_table_scan_count_replica">
Ndb_api_table_scan_count_replica
</a>
</code>
:
Number of table scans that have been started, including
scans of internal tables, by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_table_scan_count_slave">
Ndb_api_table_scan_count_slave
</a>
</code>
:
Number of table scans that have been started, including
scans of internal tables, by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_abort_count">
Ndb_api_trans_abort_count
</a>
</code>
:
Number of transactions aborted by this MySQL Server (SQL
node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_abort_count_session">
Ndb_api_trans_abort_count_session
</a>
</code>
:
Number of transactions aborted in this client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_abort_count_replica">
Ndb_api_trans_abort_count_replica
</a>
</code>
:
Number of transactions aborted by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_abort_count_slave">
Ndb_api_trans_abort_count_slave
</a>
</code>
:
Number of transactions aborted by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_close_count">
Ndb_api_trans_close_count
</a>
</code>
:
Number of transactions closed by this MySQL Server (SQL
node); may be greater than sum of TransCommitCount and
TransAbortCount.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_close_count_session">
Ndb_api_trans_close_count_session
</a>
</code>
:
Number of transactions aborted (may be greater than sum of
TransCommitCount and TransAbortCount) in this client
session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_close_count_replica">
Ndb_api_trans_close_count_replica
</a>
</code>
:
Number of transactions aborted (may be greater than sum of
TransCommitCount and TransAbortCount) by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_close_count_slave">
Ndb_api_trans_close_count_slave
</a>
</code>
:
Number of transactions aborted (may be greater than sum of
TransCommitCount and TransAbortCount) by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_commit_count">
Ndb_api_trans_commit_count
</a>
</code>
:
Number of transactions committed by this MySQL Server (SQL
node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_commit_count_session">
Ndb_api_trans_commit_count_session
</a>
</code>
:
Number of transactions committed in this client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_commit_count_replica">
Ndb_api_trans_commit_count_replica
</a>
</code>
:
Number of transactions committed by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_commit_count_slave">
Ndb_api_trans_commit_count_slave
</a>
</code>
:
Number of transactions committed by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_local_read_row_count">
Ndb_api_trans_local_read_row_count
</a>
</code>
:
Total number of rows that have been read by this MySQL
Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_local_read_row_count_session">
Ndb_api_trans_local_read_row_count_session
</a>
</code>
:
Total number of rows that have been read in this client
session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_local_read_row_count_replica">
Ndb_api_trans_local_read_row_count_replica
</a>
</code>
:
Total number of rows that have been read by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_local_read_row_count_slave">
Ndb_api_trans_local_read_row_count_slave
</a>
</code>
:
Total number of rows that have been read by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_start_count">
Ndb_api_trans_start_count
</a>
</code>
:
Number of transactions started by this MySQL Server (SQL
node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_start_count_session">
Ndb_api_trans_start_count_session
</a>
</code>
:
Number of transactions started in this client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_start_count_replica">
Ndb_api_trans_start_count_replica
</a>
</code>
:
Number of transactions started by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_trans_start_count_slave">
Ndb_api_trans_start_count_slave
</a>
</code>
:
Number of transactions started by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_uk_op_count">
Ndb_api_uk_op_count
</a>
</code>
:
Number of operations based on or using unique keys by this
MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_uk_op_count_session">
Ndb_api_uk_op_count_session
</a>
</code>
:
Number of operations based on or using unique keys in this
client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_uk_op_count_replica">
Ndb_api_uk_op_count_replica
</a>
</code>
:
Number of operations based on or using unique keys by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_uk_op_count_slave">
Ndb_api_uk_op_count_slave
</a>
</code>
:
Number of operations based on or using unique keys by this
replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_exec_complete_count">
Ndb_api_wait_exec_complete_count
</a>
</code>
:
Number of times thread has been blocked while waiting for
operation execution to complete by this MySQL Server (SQL
node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_exec_complete_count_session">
Ndb_api_wait_exec_complete_count_session
</a>
</code>
:
Number of times thread has been blocked while waiting for
operation execution to complete in this client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_exec_complete_count_replica">
Ndb_api_wait_exec_complete_count_replica
</a>
</code>
:
Number of times thread has been blocked while waiting for
operation execution to complete by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_exec_complete_count_slave">
Ndb_api_wait_exec_complete_count_slave
</a>
</code>
:
Number of times thread has been blocked while waiting for
operation execution to complete by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_meta_request_count">
Ndb_api_wait_meta_request_count
</a>
</code>
:
Number of times thread has been blocked waiting for
metadata-based signal by this MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_meta_request_count_session">
Ndb_api_wait_meta_request_count_session
</a>
</code>
:
Number of times thread has been blocked waiting for
metadata-based signal in this client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_meta_request_count_replica">
Ndb_api_wait_meta_request_count_replica
</a>
</code>
:
Number of times thread has been blocked waiting for
metadata-based signal by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_meta_request_count_slave">
Ndb_api_wait_meta_request_count_slave
</a>
</code>
:
Number of times thread has been blocked waiting for
metadata-based signal by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_nanos_count">
Ndb_api_wait_nanos_count
</a>
</code>
:
Total time (in nanoseconds) spent waiting for some type of
signal from data nodes by this MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_nanos_count_session">
Ndb_api_wait_nanos_count_session
</a>
</code>
:
Total time (in nanoseconds) spent waiting for some type of
signal from data nodes in this client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_nanos_count_replica">
Ndb_api_wait_nanos_count_replica
</a>
</code>
:
Total time (in nanoseconds) spent waiting for some type of
signal from data nodes by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_nanos_count_slave">
Ndb_api_wait_nanos_count_slave
</a>
</code>
:
Total time (in nanoseconds) spent waiting for some type of
signal from data nodes by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_scan_result_count">
Ndb_api_wait_scan_result_count
</a>
</code>
:
Number of times thread has been blocked while waiting for
scan-based signal by this MySQL Server (SQL node).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_scan_result_count_session">
Ndb_api_wait_scan_result_count_session
</a>
</code>
:
Number of times thread has been blocked while waiting for
scan-based signal in this client session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_scan_result_count_replica">
Ndb_api_wait_scan_result_count_replica
</a>
</code>
:
Number of times thread has been blocked while waiting for
scan-based signal by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_api_wait_scan_result_count_slave">
Ndb_api_wait_scan_result_count_slave
</a>
</code>
:
Number of times thread has been blocked while waiting for
scan-based signal by this replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_autoincrement_prefetch_sz">
ndb_autoincrement_prefetch_sz
</a>
</code>
:
NDB auto-increment prefetch size.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_clear_apply_status">
ndb_clear_apply_status
</a>
</code>
:
Causes RESET SLAVE/RESET REPLICA to clear all rows from
ndb_apply_status table; ON by default.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_cluster_node_id">
Ndb_cluster_node_id
</a>
</code>
:
Node ID of this server when acting as NDB Cluster SQL node.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_config_from_host">
Ndb_config_from_host
</a>
</code>
:
NDB Cluster management server host name or IP address.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_config_from_port">
Ndb_config_from_port
</a>
</code>
:
Port for connecting to NDB Cluster management server.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_config_generation">
Ndb_config_generation
</a>
</code>
:
Generation number of the current configuration of the
cluster.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_epoch">
Ndb_conflict_fn_epoch
</a>
</code>
:
Number of rows that have been found in conflict by
NDB$EPOCH() NDB replication conflict detection function.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_epoch2">
Ndb_conflict_fn_epoch2
</a>
</code>
:
Number of rows that have been found in conflict by NDB
replication NDB$EPOCH2() conflict detection function.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_epoch2_trans">
Ndb_conflict_fn_epoch2_trans
</a>
</code>
:
Number of rows that have been found in conflict by NDB
replication NDB$EPOCH2_TRANS() conflict detection function.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_epoch_trans">
Ndb_conflict_fn_epoch_trans
</a>
</code>
:
Number of rows that have been found in conflict by
NDB$EPOCH_TRANS() conflict detection function.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_max">
Ndb_conflict_fn_max
</a>
</code>
:
Number of times that NDB replication conflict resolution
based on "greater timestamp wins" has been applied to update
and delete operations.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_max_del_win">
Ndb_conflict_fn_max_del_win
</a>
</code>
:
Number of times that NDB replication conflict resolution
based on outcome of NDB$MAX_DELETE_WIN() has been applied to
update and delete operations.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_max_ins">
Ndb_conflict_fn_max_ins
</a>
</code>
:
Number of times that NDB replication conflict resolution
based on "greater timestamp wins" has been applied to insert
operations.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_max_del_win_ins">
Ndb_conflict_fn_max_del_win_ins
</a>
</code>
:
Number of times that NDB replication conflict resolution
based on outcome of NDB$MAX_DEL_WIN_INS() has been applied
to insert operations.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_fn_old">
Ndb_conflict_fn_old
</a>
</code>
:
Number of times that NDB replication "same timestamp wins"
conflict resolution has been applied.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_last_conflict_epoch">
Ndb_conflict_last_conflict_epoch
</a>
</code>
:
Most recent NDB epoch on this replica in which some conflict
was detected.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_last_stable_epoch">
Ndb_conflict_last_stable_epoch
</a>
</code>
:
Most recent epoch containing no conflicts.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_reflected_op_discard_count">
Ndb_conflict_reflected_op_discard_count
</a>
</code>
:
Number of reflected operations that were not applied due
error during execution.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_reflected_op_prepare_count">
Ndb_conflict_reflected_op_prepare_count
</a>
</code>
:
Number of reflected operations received that have been
prepared for execution.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_refresh_op_count">
Ndb_conflict_refresh_op_count
</a>
</code>
:
Number of refresh operations that have been prepared.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_conflict_role">
ndb_conflict_role
</a>
</code>
:
Role for replica to play in conflict detection and
resolution. Value is one of PRIMARY, SECONDARY, PASS, or
NONE (default). Can be changed only when replication SQL
thread is stopped. See documentation for further
information.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_trans_conflict_commit_count">
Ndb_conflict_trans_conflict_commit_count
</a>
</code>
:
Number of epoch transactions committed after requiring
transactional conflict handling.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_trans_detect_iter_count">
Ndb_conflict_trans_detect_iter_count
</a>
</code>
:
Number of internal iterations required to commit epoch
transaction. Should be (slightly) greater than or equal to
Ndb_conflict_trans_conflict_commit_count.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_trans_reject_count">
Ndb_conflict_trans_reject_count
</a>
</code>
:
Number of transactions rejected after being found in
conflict by transactional conflict function.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_trans_row_conflict_count">
Ndb_conflict_trans_row_conflict_count
</a>
</code>
:
Number of rows found in conflict by transactional conflict
function. Includes any rows included in or dependent on
conflicting transactions.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_conflict_trans_row_reject_count">
Ndb_conflict_trans_row_reject_count
</a>
</code>
:
Total number of rows realigned after being found in conflict
by transactional conflict function. Includes
Ndb_conflict_trans_row_conflict_count and any rows included
in or dependent on conflicting transactions.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_data_node_neighbour">
ndb_data_node_neighbour
</a>
</code>
:
Specifies cluster data node "closest" to this MySQL Server,
for transaction hinting and fully replicated tables.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_default_column_format">
ndb_default_column_format
</a>
</code>
:
Sets default row format and column format (FIXED or DYNAMIC)
used for new NDB tables.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_deferred_constraints">
ndb_deferred_constraints
</a>
</code>
:
Specifies that constraint checks should be deferred (where
these are supported). Not normally needed or used; for
testing purposes only.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_dbg_check_shares">
ndb_dbg_check_shares
</a>
</code>
:
Check for any lingering shares (debug builds only).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-schema-dist-timeout">
ndb-schema-dist-timeout
</a>
</code>
:
How long to wait before detecting timeout during schema
distribution.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_distribution">
ndb_distribution
</a>
</code>
:
Default distribution for new tables in NDBCLUSTER (KEYHASH
or LINHASH, default is KEYHASH).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_epoch_delete_delete_count">
Ndb_epoch_delete_delete_count
</a>
</code>
:
Number of delete-delete conflicts detected (delete operation
is applied, but row does not exist).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_eventbuffer_free_percent">
ndb_eventbuffer_free_percent
</a>
</code>
:
Percentage of free memory that should be available in event
buffer before resumption of buffering, after reaching limit
set by ndb_eventbuffer_max_alloc.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_eventbuffer_max_alloc">
ndb_eventbuffer_max_alloc
</a>
</code>
:
Maximum memory that can be allocated for buffering events by
NDB API. Defaults to 0 (no limit).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_execute_count">
Ndb_execute_count
</a>
</code>
:
Number of round trips to NDB kernel made by operations.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_extra_logging">
ndb_extra_logging
</a>
</code>
:
Controls logging of NDB Cluster schema, connection, and data
distribution events in MySQL error log.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_force_send">
ndb_force_send
</a>
</code>
:
Forces sending of buffers to NDB immediately, without
waiting for other threads.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_fully_replicated">
ndb_fully_replicated
</a>
</code>
:
Whether new NDB tables are fully replicated.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_index_stat_enable">
ndb_index_stat_enable
</a>
</code>
:
Use NDB index statistics in query optimization.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_index_stat_option">
ndb_index_stat_option
</a>
</code>
:
Comma-separated list of tunable options for NDB index
statistics; list should contain no spaces.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_join_pushdown">
ndb_join_pushdown
</a>
</code>
:
Enables pushing down of joins to data nodes.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_last_commit_epoch_server">
Ndb_last_commit_epoch_server
</a>
</code>
:
Epoch most recently committed by NDB.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_last_commit_epoch_session">
Ndb_last_commit_epoch_session
</a>
</code>
:
Epoch most recently committed by this NDB client.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_apply_status">
ndb_log_apply_status
</a>
</code>
:
Whether or not MySQL server acting as replica logs
mysql.ndb_apply_status updates received from its immediate
source in its own binary log, using its own server ID.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_bin">
ndb_log_bin
</a>
</code>
:
Write updates to NDB tables in binary log. Effective only if
binary logging is enabled with --log-bin.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_binlog_index">
ndb_log_binlog_index
</a>
</code>
:
Insert mapping between epochs and binary log positions into
ndb_binlog_index table. Defaults to ON. Effective only if
binary logging is enabled.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_cache_size">
ndb_log_cache_size
</a>
</code>
:
Set size of transaction cache used for recording NDB binary
log.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_empty_epochs">
ndb_log_empty_epochs
</a>
</code>
:
When enabled, epochs in which there were no changes are
written to ndb_apply_status and ndb_binlog_index tables,
even when log_replica_updates or log_slave_updates is
enabled.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_empty_update">
ndb_log_empty_update
</a>
</code>
:
When enabled, updates which produce no changes are written
to ndb_apply_status and ndb_binlog_index tables, even when
log_replica_updates or log_slave_updates is enabled.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_exclusive_reads">
ndb_log_exclusive_reads
</a>
</code>
:
Log primary key reads with exclusive locks; allow conflict
resolution based on read conflicts.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_orig">
ndb_log_orig
</a>
</code>
:
Whether id and epoch of originating server are recorded in
mysql.ndb_binlog_index table. Set using --ndb-log-orig
option when starting mysqld.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_transaction_id">
ndb_log_transaction_id
</a>
</code>
:
Whether NDB transaction IDs are written into binary log
(Read-only).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_transaction_compression">
ndb_log_transaction_compression
</a>
</code>
:
Whether to compress NDB binary log; can also be enabled on
startup by enabling --binlog-transaction-compression option.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_transaction_compression_level_zstd">
ndb_log_transaction_compression_level_zstd
</a>
</code>
:
The ZSTD compression level to use when writing compressed
transactions to the NDB binary log.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_metadata_check">
ndb_metadata_check
</a>
</code>
:
Enable auto-detection of NDB metadata changes with respect
to MySQL data dictionary; enabled by default.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_metadata_check_interval">
ndb_metadata_check_interval
</a>
</code>
:
Interval in seconds to perform check for NDB metadata
changes with respect to MySQL data dictionary.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_metadata_detected_count">
Ndb_metadata_detected_count
</a>
</code>
:
Number of times NDB metadata change monitor thread has
detected changes.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_metadata_excluded_count">
Ndb_metadata_excluded_count
</a>
</code>
:
Number of NDB metadata objects that NDB binlog thread has
failed to synchronize.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_metadata_sync">
ndb_metadata_sync
</a>
</code>
:
Triggers immediate synchronization of all changes between
NDB dictionary and MySQL data dictionary; causes
ndb_metadata_check and ndb_metadata_check_interval values to
be ignored. Resets to false when synchronization is
complete.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_metadata_synced_count">
Ndb_metadata_synced_count
</a>
</code>
:
Number of NDB metadata objects which have been synchronized.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_number_of_data_nodes">
Ndb_number_of_data_nodes
</a>
</code>
:
Number of data nodes in this NDB cluster; set only if server
participates in cluster.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-optimization-delay">
ndb-optimization-delay
</a>
</code>
:
Number of milliseconds to wait between processing sets of
rows by OPTIMIZE TABLE on NDB tables.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_optimized_node_selection">
ndb_optimized_node_selection
</a>
</code>
:
Determines how SQL node chooses cluster data node to use as
transaction coordinator.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_pruned_scan_count">
Ndb_pruned_scan_count
</a>
</code>
:
Number of scans executed by NDB since cluster was last
started where partition pruning could be used.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_pushed_queries_defined">
Ndb_pushed_queries_defined
</a>
</code>
:
Number of joins that API nodes have attempted to push down
to data nodes.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_pushed_queries_dropped">
Ndb_pushed_queries_dropped
</a>
</code>
:
Number of joins that API nodes have tried to push down, but
failed.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_pushed_queries_executed">
Ndb_pushed_queries_executed
</a>
</code>
:
Number of joins successfully pushed down and executed on
data nodes.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_pushed_reads">
Ndb_pushed_reads
</a>
</code>
:
Number of reads executed on data nodes by pushed-down joins.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_read_backup">
ndb_read_backup
</a>
</code>
:
Enable read from any replica for all NDB tables; use
NDB_TABLE=READ_BACKUP={0|1} with CREATE TABLE or ALTER TABLE
to enable or disable for individual NDB tables.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_recv_thread_activation_threshold">
ndb_recv_thread_activation_threshold
</a>
</code>
:
Activation threshold when receive thread takes over polling
of cluster connection (measured in concurrently active
threads).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_recv_thread_cpu_mask">
ndb_recv_thread_cpu_mask
</a>
</code>
:
CPU mask for locking receiver threads to specific CPUs;
specified as hexadecimal. See documentation for details.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_replica_max_replicated_epoch">
Ndb_replica_max_replicated_epoch
</a>
</code>
:
Most recently committed NDB epoch on this replica. When this
value is greater than or equal to
Ndb_conflict_last_conflict_epoch, no conflicts have yet been
detected.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_replica_batch_size">
ndb_replica_batch_size
</a>
</code>
:
Batch size in bytes for replica applier.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_report_thresh_binlog_epoch_slip">
ndb_report_thresh_binlog_epoch_slip
</a>
</code>
:
NDB 7.5 and later: Threshold for number of epochs completely
buffered, but not yet consumed by binlog injector thread
which when exceeded generates BUFFERED_EPOCHS_OVER_THRESHOLD
event buffer status message; prior to NDB 7.5: Threshold for
number of epochs to lag behind before reporting binary log
status.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_report_thresh_binlog_mem_usage">
ndb_report_thresh_binlog_mem_usage
</a>
</code>
:
Threshold for percentage of free memory remaining before
reporting binary log status.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_row_checksum">
ndb_row_checksum
</a>
</code>
:
When enabled, set row checksums; enabled by default.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_scan_count">
Ndb_scan_count
</a>
</code>
:
Total number of scans executed by NDB since cluster was last
started.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_schema_dist_lock_wait_timeout">
ndb_schema_dist_lock_wait_timeout
</a>
</code>
:
Time during schema distribution to wait for lock before
returning error.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_schema_dist_timeout">
ndb_schema_dist_timeout
</a>
</code>
:
Time to wait before detecting timeout during schema
distribution.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_schema_dist_upgrade_allowed">
ndb_schema_dist_upgrade_allowed
</a>
</code>
:
Allow schema distribution table upgrade when connecting to
NDB.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_show_foreign_key_mock_tables">
ndb_show_foreign_key_mock_tables
</a>
</code>
:
Show mock tables used to support foreign_key_checks=0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_slave_conflict_role">
ndb_slave_conflict_role
</a>
</code>
:
Role for replica to play in conflict detection and
resolution. Value is one of PRIMARY, SECONDARY, PASS, or
NONE (default). Can be changed only when replication SQL
thread is stopped. See documentation for further
information.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_slave_max_replicated_epoch">
Ndb_slave_max_replicated_epoch
</a>
</code>
:
Most recently committed NDB epoch on this replica. When this
value is greater than or equal to
Ndb_conflict_last_conflict_epoch, no conflicts have yet been
detected.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_system_name">
Ndb_system_name
</a>
</code>
:
Configured cluster system name; empty if server not
connected to NDB.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_table_no_logging">
ndb_table_no_logging
</a>
</code>
:
NDB tables created when this setting is enabled are not
checkpointed to disk (although table schema files are
created). Setting in effect when table is created with or
altered to use NDBCLUSTER persists for table's lifetime.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_table_temporary">
ndb_table_temporary
</a>
</code>
:
NDB tables are not persistent on disk: no schema files are
created and tables are not logged.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#statvar_Ndb_trans_hint_count_session">
Ndb_trans_hint_count_session
</a>
</code>
:
Number of transactions using hints that have been started in
this session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_use_copying_alter_table">
ndb_use_copying_alter_table
</a>
</code>
:
Use copying ALTER TABLE operations in NDB Cluster.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_use_exact_count">
ndb_use_exact_count
</a>
</code>
:
Forces NDB to use a count of records during SELECT COUNT(*)
query planning to speed up this type of query.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_use_transactions">
ndb_use_transactions
</a>
</code>
:
Set to OFF, to disable transaction support by NDB. Not
recommended except in certain special cases; see
documentation for details.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_version">
ndb_version
</a>
</code>
:
Shows build and NDB engine version as an integer.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_version_string">
ndb_version_string
</a>
</code>
:
Shows build information including NDB engine version in
ndb-x.y.z format.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndbcluster">
ndbcluster
</a>
</code>
:
Enable NDB Cluster (if this version of MySQL supports it).
Disabled by
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_skip-ndbcluster">
<code class="option">
--skip-ndbcluster
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndbinfo">
ndbinfo
</a>
</code>
:
Enable ndbinfo plugin, if supported.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndbinfo_database">
ndbinfo_database
</a>
</code>
:
Name used for NDB information database; read only.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndbinfo_max_bytes">
ndbinfo_max_bytes
</a>
</code>
:
Used for debugging only.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndbinfo_max_rows">
ndbinfo_max_rows
</a>
</code>
:
Used for debugging only.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndbinfo_offline">
ndbinfo_offline
</a>
</code>
:
Put ndbinfo database into offline mode, in which no rows are
returned from tables or views.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndbinfo_show_hidden">
ndbinfo_show_hidden
</a>
</code>
:
Whether to show ndbinfo internal base tables in mysql
client; default is OFF.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndbinfo_table_prefix">
ndbinfo_table_prefix
</a>
</code>
:
Prefix to use for naming ndbinfo internal base tables; read
only.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndbinfo_version">
ndbinfo_version
</a>
</code>
:
ndbinfo engine version; read only.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_replica_allow_batching">
replica_allow_batching
</a>
</code>
:
Turns update batching on and off for replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_server_id_bits">
server_id_bits
</a>
</code>
:
Number of least significant bits in server_id actually used
for identifying server, permitting NDB API applications to
store application data in most significant bits. server_id
must be less than 2 to power of this value.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_skip-ndbcluster">
skip-ndbcluster
</a>
</code>
:
Disable NDB Cluster storage engine.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_slave_allow_batching">
slave_allow_batching
</a>
</code>
:
Turns update batching on and off for replica.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<a class="link" href="mysql-cluster-options-variables.html#sysvar_transaction_allow_batching">
transaction_allow_batching
</a>
</code>
:
Allows batching of statements within one transaction.
Disable AUTOCOMMIT to use.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-pre-filtering.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="performance-schema-pre-filtering">
</a>
29.4.3 Event Pre-Filtering
</h3>
</div>
</div>
</div>
<p>
Pre-filtering is done by the Performance Schema and has a global
effect that applies to all users. Pre-filtering can be applied
to either the producer or consumer stage of event processing:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
To configure pre-filtering at the producer stage, several
tables can be used:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="performance-schema-setup-instruments-table.html" title="29.12.2.3 The setup_instruments Table">
<code class="literal">
setup_instruments
</code>
</a>
indicates
which instruments are available. An instrument disabled
in this table produces no events regardless of the
contents of the other production-related setup tables.
An instrument enabled in this table is permitted to
produce events, subject to the contents of the other
tables.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-setup-objects-table.html" title="29.12.2.4 The setup_objects Table">
<code class="literal">
setup_objects
</code>
</a>
controls
whether the Performance Schema monitors particular table
and stored program objects.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-threads-table.html" title="29.12.22.8 The threads Table">
<code class="literal">
threads
</code>
</a>
indicates whether
monitoring is enabled for each server thread.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="performance-schema-setup-actors-table.html" title="29.12.2.1 The setup_actors Table">
<code class="literal">
setup_actors
</code>
</a>
determines the
initial monitoring state for new foreground threads.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
To configure pre-filtering at the consumer stage, modify the
<a class="link" href="performance-schema-setup-consumers-table.html" title="29.12.2.2 The setup_consumers Table">
<code class="literal">
setup_consumers
</code>
</a>
table. This
determines the destinations to which events are sent.
<a class="link" href="performance-schema-setup-consumers-table.html" title="29.12.2.2 The setup_consumers Table">
<code class="literal">
setup_consumers
</code>
</a>
also implicitly
affects event production. If a given event is not sent to
any destination (that is, it is never consumed), the
Performance Schema does not produce it.
</p>
</li>
</ul>
</div>
<p>
Modifications to any of these tables affect monitoring
immediately, with the exception that modifications to the
<a class="link" href="performance-schema-setup-actors-table.html" title="29.12.2.1 The setup_actors Table">
<code class="literal">
setup_actors
</code>
</a>
table affect only
foreground threads created subsequent to the modification, not
existing threads.
</p>
<p>
When you change the monitoring configuration, the Performance
Schema does not flush the history tables. Events already
collected remain in the current-events and history tables until
displaced by newer events. If you disable instruments, you might
need to wait a while before events for them are displaced by
newer events of interest. Alternatively, use
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
to empty the
history tables.
</p>
<p>
After making instrumentation changes, you might want to truncate
the summary tables. Generally, the effect is to reset the
summary columns to 0 or
<code class="literal">
NULL
</code>
, not to remove
rows. This enables you to clear collected values and restart
aggregation. That might be useful, for example, after you have
made a runtime configuration change. Exceptions to this
truncation behavior are noted in individual summary table
sections.
</p>
<p>
The following sections describe how to use specific tables to
control Performance Schema pre-filtering.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/create-user.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="create-user">
</a>
15.7.1.3 CREATE USER Statement
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045174571200">
</a>
<a class="indexterm" name="idm46045174570128">
</a>
<a class="indexterm" name="idm46045174568640">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa14368259"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token punctuation">[</span><span class="token keyword">IF</span> <span class="token operator">NOT</span> <span class="token keyword">EXISTS</span><span class="token punctuation">]</span>
<span class="token keyword"><em class="replaceable">user</em></span> <span class="token punctuation">[</span><em class="replaceable">auth_option</em><span class="token punctuation">]</span> <span class="token punctuation">[</span><span class="token punctuation">,</span> <span class="token keyword"><em class="replaceable">user</em></span> <span class="token punctuation">[</span><em class="replaceable">auth_option</em><span class="token punctuation">]</span><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token keyword">DEFAULT</span> <span class="token keyword">ROLE</span> <span class="token keyword"><em class="replaceable">role</em></span> <span class="token punctuation">[</span><span class="token punctuation">,</span> <span class="token keyword"><em class="replaceable">role</em></span> <span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token punctuation">[</span><span class="token keyword">REQUIRE</span> {<span class="token keyword">NONE</span> <span class="token operator">|</span> <em class="replaceable">tls_option</em> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token operator">AND</span><span class="token punctuation">]</span> <em class="replaceable">tls_option</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>}<span class="token punctuation">]</span>
<span class="token punctuation">[</span><span class="token keyword">WITH</span> <em class="replaceable">resource_option</em> <span class="token punctuation">[</span><em class="replaceable">resource_option</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">]</span>
<span class="token punctuation">[</span><em class="replaceable">password_option</em> <span class="token operator">|</span> <em class="replaceable">lock_option</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token punctuation">[</span><span class="token keyword">COMMENT</span> <span class="token string">'<em class="replaceable">comment_string</em>'</span> <span class="token operator">|</span> <span class="token keyword">ATTRIBUTE</span> <span class="token string">'<em class="replaceable">json_object</em>'</span><span class="token punctuation">]</span>
<span class="token keyword"><em class="replaceable">user</em></span>:
<span class="token punctuation">(</span>see Section <span class="token number">8.2</span><span class="token punctuation">.</span><span class="token number">4</span><span class="token punctuation">,</span> “Specifying <span class="token keyword">Account</span> <span class="token keyword">Names</span>”<span class="token punctuation">)</span>
<em class="replaceable">auth_option</em>: {
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">2fa_auth_option</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">2fa_auth_option</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">2fa_auth_option</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">2fa_auth_option</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token keyword">BY</span> <span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">2fa_auth_option</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token keyword">AS</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">2fa_auth_option</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token punctuation">[</span><em class="replaceable">initial_auth_option</em><span class="token punctuation">]</span>
}
<em class="replaceable">2fa_auth_option</em>: {
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">3fa_auth_option</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">3fa_auth_option</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">3fa_auth_option</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">3fa_auth_option</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token keyword">BY</span> <span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">3fa_auth_option</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token keyword">AS</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span> <span class="token punctuation">[</span><span class="token operator">AND</span> <em class="replaceable">3fa_auth_option</em><span class="token punctuation">]</span>
}
<em class="replaceable">3fa_auth_option</em>: {
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token keyword">BY</span> <span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span>
<span class="token operator">|</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token keyword">AS</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span>
}
<em class="replaceable">initial_auth_option</em>: {
INITIAL AUTHENTICATION <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> {<span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span> <span class="token operator">|</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span>}
<span class="token operator">|</span> INITIAL AUTHENTICATION <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> <em class="replaceable">auth_plugin</em> <span class="token keyword">AS</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span>
}
<em class="replaceable">tls_option</em>: {
<span class="token keyword">SSL</span>
<span class="token operator">|</span> <span class="token keyword">X509</span>
<span class="token operator">|</span> <span class="token keyword">CIPHER</span> <span class="token string">'<em class="replaceable">cipher</em>'</span>
<span class="token operator">|</span> <span class="token keyword">ISSUER</span> <span class="token string">'<em class="replaceable">issuer</em>'</span>
<span class="token operator">|</span> <span class="token keyword">SUBJECT</span> <span class="token string">'<em class="replaceable">subject</em>'</span>
}
<em class="replaceable">resource_option</em>: {
<span class="token keyword">MAX_QUERIES_PER_HOUR</span> <em class="replaceable">count</em>
<span class="token operator">|</span> <span class="token keyword">MAX_UPDATES_PER_HOUR</span> <em class="replaceable">count</em>
<span class="token operator">|</span> <span class="token keyword">MAX_CONNECTIONS_PER_HOUR</span> <em class="replaceable">count</em>
<span class="token operator">|</span> <span class="token keyword">MAX_USER_CONNECTIONS</span> <em class="replaceable">count</em>
}
<em class="replaceable">password_option</em>: {
<span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span> <span class="token punctuation">[</span><span class="token keyword">DEFAULT</span> <span class="token operator">|</span> <span class="token keyword">NEVER</span> <span class="token operator">|</span> <span class="token keyword">INTERVAL</span> <em class="replaceable">N</em> <span class="token keyword">DAY</span><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">HISTORY</span> {<span class="token keyword">DEFAULT</span> <span class="token operator">|</span> <em class="replaceable">N</em>}
<span class="token operator">|</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REUSE</span> <span class="token keyword">INTERVAL</span> {<span class="token keyword">DEFAULT</span> <span class="token operator">|</span> <em class="replaceable">N</em> <span class="token keyword">DAY</span>}
<span class="token operator">|</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">CURRENT</span> <span class="token punctuation">[</span><span class="token keyword">DEFAULT</span> <span class="token operator">|</span> <span class="token keyword">OPTIONAL</span><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">FAILED_LOGIN_ATTEMPTS</span> <em class="replaceable">N</em>
<span class="token operator">|</span> <span class="token keyword">PASSWORD_LOCK_TIME</span> {<em class="replaceable">N</em> <span class="token operator">|</span> <span class="token keyword">UNBOUNDED</span>}
}
<em class="replaceable">lock_option</em>: {
<span class="token keyword">ACCOUNT</span> <span class="token keyword">LOCK</span>
<span class="token operator">|</span> <span class="token keyword">ACCOUNT</span> <span class="token keyword">UNLOCK</span>
}</code></pre>
</div>
<p>
The
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
statement creates
new MySQL accounts. It enables authentication, role, SSL/TLS,
resource-limit, password-management, comment, and attribute
properties to be established for new accounts. It also controls
whether accounts are initially locked or unlocked.
</p>
<p>
To use
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
, you must have
the global
<a class="link" href="privileges-provided.html#priv_create-user">
<code class="literal">
CREATE USER
</code>
</a>
privilege,
or the
<a class="link" href="privileges-provided.html#priv_insert">
<code class="literal">
INSERT
</code>
</a>
privilege for the
<code class="literal">
mysql
</code>
system schema. When the
<a class="link" href="server-system-variables.html#sysvar_read_only">
<code class="literal">
read_only
</code>
</a>
system variable is
enabled,
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
additionally
requires the
<a class="link" href="privileges-provided.html#priv_connection-admin">
<code class="literal">
CONNECTION_ADMIN
</code>
</a>
privilege (or the deprecated
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege).
</p>
<p>
These additional privilege considerations also apply:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The
<a class="link" href="server-system-variables.html#sysvar_authentication_policy">
<code class="literal">
authentication_policy
</code>
</a>
system variable places certain constraints on how the
authentication-related clauses of
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
statements may be
used; for details, see the description of that variable.
These constraints do not apply if you have the
<a class="link" href="privileges-provided.html#priv_authentication-policy-admin">
<code class="literal">
AUTHENTICATION_POLICY_ADMIN
</code>
</a>
privilege.
</p>
</li>
<li class="listitem">
<p>
To create an account that uses passwordless authentication,
you must have the
<a class="link" href="privileges-provided.html#priv_passwordless-user-admin">
<code class="literal">
PASSWORDLESS_USER_ADMIN
</code>
</a>
privilege.
</p>
</li>
</ul>
</div>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
fails with an error
if any account to be created is named as the
<code class="literal">
DEFINER
</code>
attribute for any stored object.
(That is, the statement fails if creating an account would cause
the account to adopt a currently orphaned stored object.) To
perform the operation anyway, you must have the
<a class="link" href="privileges-provided.html#priv_set-any-definer">
<code class="literal">
SET_ANY_DEFINER
</code>
</a>
or
<a class="link" href="privileges-provided.html#priv_allow-nonexistent-definer">
<code class="literal">
ALLOW_NONEXISTENT_DEFINER
</code>
</a>
privilege; in this case, the statement succeeds with a warning
rather than failing with an error. To perform the user-creation
operation without either of these, drop the orphan objects,
create the account and grant its privileges, and then re-create
the dropped objects. For additional information, including how
to identify which objects name a given account as the
<code class="literal">
DEFINER
</code>
attribute, see
<a class="xref" href="stored-objects-security.html#stored-objects-security-orphan-objects" title="Orphan Stored Objects">
Orphan Stored Objects
</a>
.
</p>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
either succeeds for
all named users or rolls back and has no effect if any error
occurs. By default, an error occurs if you try to create a user
that already exists. If the
<code class="literal">
IF NOT EXISTS
</code>
clause is given, the statement produces a warning for each named
user that already exists, rather than an error.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
Under some circumstances,
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE
USER
</code>
</a>
may be recorded in server logs or on the client
side in a history file such as
<code class="filename">
~/.mysql_history
</code>
, which means that
cleartext passwords may be read by anyone having read access
to that information. For information about the conditions
under which this occurs for the server logs and how to control
it, see
<a class="xref" href="password-logging.html" title="8.1.2.3 Passwords and Logging">
Section 8.1.2.3, “Passwords and Logging”
</a>
. For similar
information about client-side logging, see
<a class="xref" href="mysql-logging.html" title="6.5.1.3 mysql Client Logging">
Section 6.5.1.3, “mysql Client Logging”
</a>
.
</p>
</div>
<p>
There are several aspects to the
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE
USER
</code>
</a>
statement, described under the following topics:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="create-user.html#create-user-overview" title="CREATE USER Overview">
CREATE USER Overview
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="create-user.html#create-user-authentication" title="CREATE USER Authentication Options">
CREATE USER Authentication Options
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="create-user.html#create-user-multifactor-authentication" title="CREATE USER Multifactor Authentication Options">
CREATE USER Multifactor Authentication Options
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="create-user.html#create-user-role" title="CREATE USER Role Options">
CREATE USER Role Options
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="create-user.html#create-user-tls" title="CREATE USER SSL/TLS Options">
CREATE USER SSL/TLS Options
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="create-user.html#create-user-resource-limits" title="CREATE USER Resource-Limit Options">
CREATE USER Resource-Limit Options
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="create-user.html#create-user-password-management" title="CREATE USER Password-Management Options">
CREATE USER Password-Management Options
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="create-user.html#create-user-comments-attributes" title="CREATE USER Comment and Attribute Options">
CREATE USER Comment and Attribute Options
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="create-user.html#create-user-account-locking" title="CREATE USER Account-Locking Options">
CREATE USER Account-Locking Options
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="create-user.html#create-user-binary-logging" title="CREATE USER Binary Logging">
CREATE USER Binary Logging
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="create-user-overview">
</a>
CREATE USER Overview
</h5>
</div>
</div>
</div>
<p>
For each account,
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
creates a new row in the
<code class="literal">
mysql.user
</code>
system
table. The account row reflects the properties specified in
the statement. Unspecified properties are set to their default
values:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Authentication: The default authentication plugin
(determined as described in
<a class="xref" href="pluggable-authentication.html#pluggable-authentication-default-plugin" title="The Default Authentication Plugin">
The Default Authentication Plugin
</a>
),
and empty credentials
</p>
</li>
<li class="listitem">
<p>
Default role:
<code class="literal">
NONE
</code>
</p>
</li>
<li class="listitem">
<p>
SSL/TLS:
<code class="literal">
NONE
</code>
</p>
</li>
<li class="listitem">
<p>
Resource limits: Unlimited
</p>
</li>
<li class="listitem">
<p>
Password management:
<code class="literal">
PASSWORD EXPIRE DEFAULT
PASSWORD HISTORY DEFAULT PASSWORD REUSE INTERVAL DEFAULT
PASSWORD REQUIRE CURRENT DEFAULT
</code>
; failed-login
tracking and temporary account locking are disabled
</p>
</li>
<li class="listitem">
<p>
Account locking:
<code class="literal">
ACCOUNT UNLOCK
</code>
</p>
</li>
</ul>
</div>
<p>
An account when first created has no privileges and the
default role
<code class="literal">
NONE
</code>
. To assign privileges or
roles to this account, use one or more
<a class="link" href="grant.html" title="15.7.1.6 GRANT Statement">
<code class="literal">
GRANT
</code>
</a>
statements.
</p>
<p>
Each account name uses the format described in
<a class="xref" href="account-names.html" title="8.2.4 Specifying Account Names">
Section 8.2.4, “Specifying Account Names”
</a>
. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa85234469"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">password</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The host name part of the account name, if omitted, defaults
to
<code class="literal">
'%'
</code>
. You should be aware that, while
MySQL 8.4 treats grants made to such a user as
though they had been granted to
<code class="literal">
'
<em class="replaceable">
<code>
user
</code>
</em>
'@'localhost'
</code>
,
this behavior is deprecated, and thus subject to removal in a
future version of MySQL.
</p>
<p>
Each
<em class="replaceable">
<code>
user
</code>
</em>
value naming an account
may be followed by an optional
<em class="replaceable">
<code>
auth_option
</code>
</em>
value that indicates
how the account authenticates. These values enable account
authentication plugins and credentials (for example, a
password) to be specified. Each
<em class="replaceable">
<code>
auth_option
</code>
</em>
value applies
<span class="emphasis">
<em>
only
</em>
</span>
to the account named immediately
preceding it.
</p>
<p>
Following the
<em class="replaceable">
<code>
user
</code>
</em>
specifications,
the statement may include options for SSL/TLS, resource-limit,
password-management, and locking properties. All such options
are
<span class="emphasis">
<em>
global
</em>
</span>
to the statement and apply to
<span class="emphasis">
<em>
all
</em>
</span>
accounts named in the statement.
</p>
<p>
Example: Create an account that uses the default
authentication plugin and the given password. Mark the
password expired so that the user must choose a new one at the
first connection to the server:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa38077291"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">new_password</em>'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Example: Create an account that uses the
<code class="literal">
caching_sha2_password
</code>
authentication plugin
and the given password. Require that a new password be chosen
every 180 days, and enable failed-login tracking, such that
three consecutive incorrect passwords cause temporary account
locking for two days:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa65383782"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> caching_sha2_password <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">new_password</em>'</span>
<span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span> <span class="token keyword">INTERVAL</span> <span class="token number">180</span> <span class="token keyword">DAY</span>
<span class="token keyword">FAILED_LOGIN_ATTEMPTS</span> <span class="token number">3</span> <span class="token keyword">PASSWORD_LOCK_TIME</span> <span class="token number">2</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Example: Create multiple accounts, specifying some per-account
properties and some global properties:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60272985"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span>
<span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> mysql_native_password
<span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">new_password1</em>'</span><span class="token punctuation">,</span>
<span class="token string">'jeanne'</span>@<span class="token string">'localhost'</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> caching_sha2_password
<span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">new_password2</em>'</span>
<span class="token keyword">REQUIRE</span> <span class="token keyword">X509</span> <span class="token keyword">WITH</span> <span class="token keyword">MAX_QUERIES_PER_HOUR</span> <span class="token number">60</span>
<span class="token keyword">PASSWORD</span> <span class="token keyword">HISTORY</span> <span class="token number">5</span>
<span class="token keyword">ACCOUNT</span> <span class="token keyword">LOCK</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Each
<em class="replaceable">
<code>
auth_option
</code>
</em>
value
(
<code class="literal">
IDENTIFIED WITH ... BY
</code>
in this case)
applies only to the account named immediately preceding it, so
each account uses the immediately following authentication
plugin and password.
</p>
<p>
The remaining properties apply globally to all accounts named
in the statement, so for both accounts:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Connections must be made using a valid X.509 certificate.
</p>
</li>
<li class="listitem">
<p>
Up to 60 queries per hour are permitted.
</p>
</li>
<li class="listitem">
<p>
Password changes cannot reuse any of the five most recent
passwords.
</p>
</li>
<li class="listitem">
<p>
The account is locked initially, so effectively it is a
placeholder and cannot be used until an administrator
unlocks it.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="create-user-authentication">
</a>
CREATE USER Authentication Options
</h5>
</div>
</div>
</div>
<p>
An account name may be followed by an
<em class="replaceable">
<code>
auth_option
</code>
</em>
authentication option
that specifies the account authentication plugin, credentials,
or both.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
MySQL 8.4 supports multifactor authentication
(MFA), such that accounts can have up to three
authentication methods. That is, accounts can use two-factor
authentication (2FA) or three-factor authentication (3FA).
The syntax and semantics of
<em class="replaceable">
<code>
auth_option
</code>
</em>
remain unchanged, but
<em class="replaceable">
<code>
auth_option
</code>
</em>
may be followed by
specifications for additional authentication methods. This
section describes
<em class="replaceable">
<code>
auth_option
</code>
</em>
.
For details about the optional MFA-related following
clauses, see
<a class="xref" href="create-user.html#create-user-multifactor-authentication" title="CREATE USER Multifactor Authentication Options">
CREATE USER Multifactor Authentication Options
</a>
.
</p>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Clauses for random password generation apply only to
accounts that use an authentication plugin that stores
credentials internally to MySQL. For accounts that use a
plugin that performs authentication against a credentials
system that is external to MySQL, password management must
be handled externally against that system as well. For more
information about internal credentials storage, see
<a class="xref" href="password-management.html" title="8.2.15 Password Management">
Section 8.2.15, “Password Management”
</a>
.
</p>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<em class="replaceable">
<code>
auth_plugin
</code>
</em>
names an
authentication plugin. The plugin name can be a quoted
string literal or an unquoted name. Plugin names are
stored in the
<code class="literal">
plugin
</code>
column of the
<code class="literal">
mysql.user
</code>
system table.
</p>
<p>
For
<em class="replaceable">
<code>
auth_option
</code>
</em>
syntax that
does not specify an authentication plugin, the server
assigns the default plugin, determined as described in
<a class="xref" href="pluggable-authentication.html#pluggable-authentication-default-plugin" title="The Default Authentication Plugin">
The Default Authentication Plugin
</a>
.
For descriptions of each plugin, see
<a class="xref" href="authentication-plugins.html" title="8.4.1 Authentication Plugins">
Section 8.4.1, “Authentication Plugins”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Credentials that are stored internally are stored in the
<code class="literal">
mysql.user
</code>
system table. An
<code class="literal">
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
value or
<code class="literal">
RANDOM PASSWORD
</code>
specifies
account credentials, either as a cleartext (unencrypted)
string or hashed in the format expected by the
authentication plugin associated with the account,
respectively:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
For syntax that uses
<code class="literal">
BY
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
,
the string is cleartext and is passed to the
authentication plugin for possible hashing. The result
returned by the plugin is stored in the
<code class="literal">
mysql.user
</code>
table. A plugin may use
the value as specified, in which case no hashing
occurs.
</p>
</li>
<li class="listitem">
<p>
For syntax that uses
<code class="literal">
BY RANDOM
PASSWORD
</code>
, MySQL generates a random password
and as cleartext and passes it to the authentication
plugin for possible hashing. The result returned by
the plugin is stored in the
<code class="literal">
mysql.user
</code>
table. A plugin may use
the value as specified, in which case no hashing
occurs.
</p>
<p>
Randomly generated passwords have the characteristics
described in
<a class="xref" href="password-management.html#random-password-generation" title="Random Password Generation">
Random Password Generation
</a>
.
</p>
</li>
<li class="listitem">
<p>
For syntax that uses
<code class="literal">
AS
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
,
the string is assumed to be already in the format the
authentication plugin requires, and is stored as is in
the
<code class="literal">
mysql.user
</code>
table. If a plugin
requires a hashed value, the value must be already
hashed in a format appropriate for the plugin;
otherwise, the value cannot be used by the plugin and
correct authentication of client connections does not
occur.
</p>
<p>
A hashed string can be either a string literal or a
hexadecimal value. The latter corresponds to the type
of value displayed by
<a class="link" href="show-create-user.html" title="15.7.7.13 SHOW CREATE USER Statement">
<code class="literal">
SHOW CREATE
USER
</code>
</a>
for password hashes containing
unprintable characters when the
<a class="link" href="server-system-variables.html#sysvar_print_identified_with_as_hex">
<code class="literal">
print_identified_with_as_hex
</code>
</a>
system variable is enabled.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
Although we show
<code class="literal">
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
with quotation marks, a hexadecimal value used for
this purpose must
<span class="emphasis">
<em>
not
</em>
</span>
be
quoted.
</p>
</div>
</li>
<li class="listitem">
<p>
If an authentication plugin performs no hashing of the
authentication string, the
<code class="literal">
BY
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
and
<code class="literal">
AS
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
clauses have the same effect: The authentication
string is stored as is in the
<code class="literal">
mysql.user
</code>
system table.
</p>
</li>
</ul>
</div>
</li>
</ul>
</div>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
permits these
<em class="replaceable">
<code>
auth_option
</code>
</em>
syntaxes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
IDENTIFIED BY
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
</p>
<p>
Sets the account authentication plugin to the default
plugin, passes the cleartext
<code class="literal">
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
value to the plugin for possible hashing, and stores the
result in the account row in the
<code class="literal">
mysql.user
</code>
system table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
IDENTIFIED BY RANDOM PASSWORD
</code>
</p>
<p>
Sets the account authentication plugin to the default
plugin, generates a random password, passes the cleartext
password value to the plugin for possible hashing, and
stores the result in the account row in the
<code class="literal">
mysql.user
</code>
system table. The statement
also returns the cleartext password in a result set to
make it available to the user or application executing the
statement. For details about the result set and
characteristics of randomly generated passwords, see
<a class="xref" href="password-management.html#random-password-generation" title="Random Password Generation">
Random Password Generation
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
IDENTIFIED WITH
<em class="replaceable">
<code>
auth_plugin
</code>
</em>
</code>
</p>
<p>
Sets the account authentication plugin to
<em class="replaceable">
<code>
auth_plugin
</code>
</em>
, clears the
credentials to the empty string, and stores the result in
the account row in the
<code class="literal">
mysql.user
</code>
system table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
IDENTIFIED WITH
<em class="replaceable">
<code>
auth_plugin
</code>
</em>
BY
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
</p>
<p>
Sets the account authentication plugin to
<em class="replaceable">
<code>
auth_plugin
</code>
</em>
, passes the
cleartext
<code class="literal">
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
value to the plugin for possible hashing, and stores the
result in the account row in the
<code class="literal">
mysql.user
</code>
system table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
IDENTIFIED WITH
<em class="replaceable">
<code>
auth_plugin
</code>
</em>
BY RANDOM
PASSWORD
</code>
</p>
<p>
Sets the account authentication plugin to
<em class="replaceable">
<code>
auth_plugin
</code>
</em>
, generates a random
password, passes the cleartext password value to the
plugin for possible hashing, and stores the result in the
account row in the
<code class="literal">
mysql.user
</code>
system
table. The statement also returns the cleartext password
in a result set to make it available to the user or
application executing the statement. For details about the
result set and characteristics of randomly generated
passwords, see
<a class="xref" href="password-management.html#random-password-generation" title="Random Password Generation">
Random Password Generation
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
IDENTIFIED WITH
<em class="replaceable">
<code>
auth_plugin
</code>
</em>
AS
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
</p>
<p>
Sets the account authentication plugin to
<em class="replaceable">
<code>
auth_plugin
</code>
</em>
and stores the
<code class="literal">
'
<em class="replaceable">
<code>
auth_string
</code>
</em>
'
</code>
value as is in the
<code class="literal">
mysql.user
</code>
account
row. If the plugin requires a hashed string, the string is
assumed to be already hashed in the format the plugin
requires.
</p>
</li>
</ul>
</div>
<p>
Example: Specify the password as cleartext; the default plugin
is used:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa28954059"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">password</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Example: Specify the authentication plugin, along with a
cleartext password value:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa22124779"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> mysql_native_password <span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">password</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
In each case, the password value stored in the account row is
the cleartext value
<code class="literal">
'
<em class="replaceable">
<code>
password
</code>
</em>
'
</code>
after
it has been hashed by the authentication plugin associated
with the account.
</p>
<p>
For additional information about setting passwords and
authentication plugins, see
<a class="xref" href="assigning-passwords.html" title="8.2.14 Assigning Account Passwords">
Section 8.2.14, “Assigning Account Passwords”
</a>
, and
<a class="xref" href="pluggable-authentication.html" title="8.2.17 Pluggable Authentication">
Section 8.2.17, “Pluggable Authentication”
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="create-user-multifactor-authentication">
</a>
CREATE USER Multifactor Authentication Options
</h5>
</div>
</div>
</div>
<p>
The
<em class="replaceable">
<code>
auth_option
</code>
</em>
part of
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
defines an
authentication method for one-factor/single-factor
authentication (1FA/SFA).
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE
USER
</code>
</a>
also supports multifactor authentication (MFA),
such that accounts can have up to three authentication
methods. That is, accounts can use two-factor authentication
(2FA) or three-factor authentication (3FA).
</p>
<p>
The
<a class="link" href="server-system-variables.html#sysvar_authentication_policy">
<code class="literal">
authentication_policy
</code>
</a>
system variable defines constraints for
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
statements with
multifactor authentication (MFA) clauses. For example, the
<a class="link" href="server-system-variables.html#sysvar_authentication_policy">
<code class="literal">
authentication_policy
</code>
</a>
setting
controls the number of authentication factors that accounts
may have, and for each factor, which authentication methods
are permitted. See
<a class="xref" href="multifactor-authentication.html#multifactor-authentication-policy" title="Configuring the Multifactor Authentication Policy">
Configuring the Multifactor Authentication Policy
</a>
.
</p>
<p>
For information about factor-specific rules that determine the
default authentication plugin for authentication clauses that
name no plugin, see
<a class="xref" href="pluggable-authentication.html#pluggable-authentication-default-plugin" title="The Default Authentication Plugin">
The Default Authentication Plugin
</a>
.
</p>
<p>
Following
<em class="replaceable">
<code>
auth_option
</code>
</em>
, there may
appear different optional MFA clauses:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<em class="replaceable">
<code>
2fa_auth_option
</code>
</em>
: Specifies a
factor 2 authentication method. The following example
defines
<code class="literal">
caching_sha2_password
</code>
as the
factor 1 authentication method, and
<code class="literal">
authentication_ldap_sasl
</code>
as the factor
2 authentication method.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa6816655"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'u1'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> caching_sha2_password
<span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">sha2_password</em>'</span>
<span class="token operator">AND</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> authentication_ldap_sasl
<span class="token keyword">AS</span> <span class="token string">'uid=u1_ldap,ou=People,dc=example,dc=com'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
3fa_auth_option
</code>
</em>
: Following
<em class="replaceable">
<code>
2fa_auth_option
</code>
</em>
, there may
appear a
<em class="replaceable">
<code>
3fa_auth_option
</code>
</em>
clause
to specify a factor 3 authentication method. The following
example defines
<code class="literal">
caching_sha2_password
</code>
as the factor 1 authentication method,
<code class="literal">
authentication_ldap_sasl
</code>
as the factor
2 authentication method, and
<code class="literal">
authentication_webauthn
</code>
as the factor 3
authentication method
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa84948551"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'u1'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> caching_sha2_password
<span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">sha2_password</em>'</span>
<span class="token operator">AND</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> authentication_ldap_sasl
<span class="token keyword">AS</span> <span class="token string">'uid=u1_ldap,ou=People,dc=example,dc=com'</span>
<span class="token operator">AND</span> <span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> authentication_webauthn<span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
initial_auth_option
</code>
</em>
: Specifies
an initial authentication method for configuring
FIDO/FIDO2 passwordless authentication. As shown in the
following, temporary authentication using either a
generated random password or a user-specified
<em class="replaceable">
<code>
auth-string
</code>
</em>
is required to
enable WebAuthn passwordless authentication.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa35471304"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token keyword"><em class="replaceable">user</em></span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> authentication_webauthn
INITIAL AUTHENTICATION <span class="token keyword">IDENTIFIED</span> <span class="token keyword">BY</span> {<span class="token keyword">RANDOM</span> <span class="token keyword">PASSWORD</span> <span class="token operator">|</span> <span class="token string">'<em class="replaceable">auth_string</em>'</span>}<span class="token punctuation">;</span></code></pre>
</div>
<p>
For information about configuring passwordless
authentication using WebAuthn pluggable authentication,
See
<a class="xref" href="webauthn-pluggable-authentication.html#webauthn-pluggable-authentication-passwordless" title="WebAuthn Passwordless Authentication">
WebAuthn Passwordless Authentication
</a>
.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="create-user-role">
</a>
CREATE USER Role Options
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045174340704">
</a>
<p>
The
<code class="literal">
DEFAULT ROLE
</code>
clause defines which roles
become active when the user connects to the server and
authenticates, or when the user executes the
<a class="link" href="set-role.html" title="15.7.1.11 SET ROLE Statement">
<code class="literal">
SET ROLE
DEFAULT
</code>
</a>
statement during a session.
</p>
<p>
Each role name uses the format described in
<a class="xref" href="role-names.html" title="8.2.5 Specifying Role Names">
Section 8.2.5, “Specifying Role Names”
</a>
. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa31295286"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'joe'</span>@<span class="token string">'10.0.0.1'</span> <span class="token keyword">DEFAULT</span> <span class="token keyword">ROLE</span> administrator<span class="token punctuation">,</span> developer<span class="token punctuation">;</span></code></pre>
</div>
<p>
The host name part of the role name, if omitted, defaults to
<code class="literal">
'%'
</code>
.
</p>
<p>
The
<code class="literal">
DEFAULT ROLE
</code>
clause permits a list of
one or more comma-separated role names. These roles must exist
at the time
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
is
executed; otherwise the statement raises an error
(
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_user_does_not_exist" target="_top">
<code class="literal">
ER_USER_DOES_NOT_EXIST
</code>
</a>
), and
the user is not created.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="create-user-tls">
</a>
CREATE USER SSL/TLS Options
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045174328368">
</a>
<a class="indexterm" name="idm46045174326912">
</a>
<a class="indexterm" name="idm46045174325424">
</a>
<p>
MySQL can check X.509 certificate attributes in addition to
the usual authentication that is based on the user name and
credentials. For background information on the use of SSL/TLS
with MySQL, see
<a class="xref" href="encrypted-connections.html" title="8.3 Using Encrypted Connections">
Section 8.3, “Using Encrypted Connections”
</a>
.
</p>
<p>
To specify SSL/TLS-related options for a MySQL account, use a
<code class="literal">
REQUIRE
</code>
clause that specifies one or more
<em class="replaceable">
<code>
tls_option
</code>
</em>
values.
</p>
<p>
Order of
<code class="literal">
REQUIRE
</code>
options does not matter,
but no option can be specified twice. The
<code class="literal">
AND
</code>
keyword is optional between
<code class="literal">
REQUIRE
</code>
options.
</p>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
permits these
<em class="replaceable">
<code>
tls_option
</code>
</em>
values:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
NONE
</code>
</p>
<p>
Indicates that all accounts named by the statement have no
SSL or X.509 requirements. Unencrypted connections are
permitted if the user name and password are valid.
Encrypted connections can be used, at the client's option,
if the client has the proper certificate and key files.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa52400298"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">NONE</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Clients attempt to establish a secure connection by
default. For clients that have
<code class="literal">
REQUIRE
NONE
</code>
, the connection attempt falls back to an
unencrypted connection if a secure connection cannot be
established. To require an encrypted connection, a client
need specify only the
<a class="link" href="connection-options.html#option_general_ssl-mode">
<code class="option">
--ssl-mode=REQUIRED
</code>
</a>
option; the connection attempt fails if a secure
connection cannot be established.
</p>
<p>
<code class="literal">
NONE
</code>
is the default if no SSL-related
<code class="literal">
REQUIRE
</code>
options are specified.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
SSL
</code>
</p>
<p>
Tells the server to permit only encrypted connections for
all accounts named by the statement.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa65846461"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">SSL</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Clients attempt to establish a secure connection by
default. For accounts that have
<code class="literal">
REQUIRE
SSL
</code>
, the connection attempt fails if a secure
connection cannot be established.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
X509
</code>
</p>
<p>
For all accounts named by the statement, requires that
clients present a valid certificate, but the exact
certificate, issuer, and subject do not matter. The only
requirement is that it should be possible to verify its
signature with one of the CA certificates. Use of X.509
certificates always implies encryption, so the
<code class="literal">
SSL
</code>
option is unnecessary in this case.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa9249583"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">X509</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For accounts with
<code class="literal">
REQUIRE X509
</code>
, clients
must specify the
<a class="link" href="connection-options.html#option_general_ssl-key">
<code class="option">
--ssl-key
</code>
</a>
and
<a class="link" href="connection-options.html#option_general_ssl-cert">
<code class="option">
--ssl-cert
</code>
</a>
options to
connect. (It is recommended but not required that
<a class="link" href="connection-options.html#option_general_ssl-ca">
<code class="option">
--ssl-ca
</code>
</a>
also be specified
so that the public certificate provided by the server can
be verified.) This is true for
<code class="literal">
ISSUER
</code>
and
<code class="literal">
SUBJECT
</code>
as well because those
<code class="literal">
REQUIRE
</code>
options imply the requirements
of
<code class="literal">
X509
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ISSUER
'
<em class="replaceable">
<code>
issuer
</code>
</em>
'
</code>
</p>
<p>
For all accounts named by the statement, requires that
clients present a valid X.509 certificate issued by CA
<code class="literal">
'
<em class="replaceable">
<code>
issuer
</code>
</em>
'
</code>
. If
a client presents a certificate that is valid but has a
different issuer, the server rejects the connection. Use
of X.509 certificates always implies encryption, so the
<code class="literal">
SSL
</code>
option is unnecessary in this case.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51748374"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">REQUIRE</span> <span class="token keyword">ISSUER</span> <span class="token string">'/C=SE/ST=Stockholm/L=Stockholm/
O=MySQL/CN=CA/emailAddress=ca@example.com'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Because
<code class="literal">
ISSUER
</code>
implies the requirements
of
<code class="literal">
X509
</code>
, clients must specify the
<a class="link" href="connection-options.html#option_general_ssl-key">
<code class="option">
--ssl-key
</code>
</a>
and
<a class="link" href="connection-options.html#option_general_ssl-cert">
<code class="option">
--ssl-cert
</code>
</a>
options to
connect. (It is recommended but not required that
<a class="link" href="connection-options.html#option_general_ssl-ca">
<code class="option">
--ssl-ca
</code>
</a>
also be specified
so that the public certificate provided by the server can
be verified.)
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
SUBJECT
'
<em class="replaceable">
<code>
subject
</code>
</em>
'
</code>
</p>
<p>
For all accounts named by the statement, requires that
clients present a valid X.509 certificate containing the
subject
<em class="replaceable">
<code>
subject
</code>
</em>
. If a client
presents a certificate that is valid but has a different
subject, the server rejects the connection. Use of X.509
certificates always implies encryption, so the
<code class="literal">
SSL
</code>
option is unnecessary in this case.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa25236951"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">REQUIRE</span> <span class="token keyword">SUBJECT</span> <span class="token string">'/C=SE/ST=Stockholm/L=Stockholm/
O=MySQL demo client certificate/
CN=client/emailAddress=client@example.com'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
MySQL does a simple string comparison of the
<code class="literal">
'
<em class="replaceable">
<code>
subject
</code>
</em>
'
</code>
value to the value in the certificate, so lettercase and
component ordering must be given exactly as present in the
certificate.
</p>
<p>
Because
<code class="literal">
SUBJECT
</code>
implies the
requirements of
<code class="literal">
X509
</code>
, clients must
specify the
<a class="link" href="connection-options.html#option_general_ssl-key">
<code class="option">
--ssl-key
</code>
</a>
and
<a class="link" href="connection-options.html#option_general_ssl-cert">
<code class="option">
--ssl-cert
</code>
</a>
options to
connect. (It is recommended but not required that
<a class="link" href="connection-options.html#option_general_ssl-ca">
<code class="option">
--ssl-ca
</code>
</a>
also be specified
so that the public certificate provided by the server can
be verified.)
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CIPHER
'
<em class="replaceable">
<code>
cipher
</code>
</em>
'
</code>
</p>
<p>
For all accounts named by the statement, requires a
specific cipher method for encrypting connections. This
option is needed to ensure that ciphers and key lengths of
sufficient strength are used. Encryption can be weak if
old algorithms using short encryption keys are used.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16588616"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">REQUIRE</span> <span class="token keyword">CIPHER</span> <span class="token string">'EDH-RSA-DES-CBC3-SHA'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
The
<code class="literal">
SUBJECT
</code>
,
<code class="literal">
ISSUER
</code>
, and
<code class="literal">
CIPHER
</code>
options can be combined in the
<code class="literal">
REQUIRE
</code>
clause:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa23820739"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">REQUIRE</span> <span class="token keyword">SUBJECT</span> <span class="token string">'/C=SE/ST=Stockholm/L=Stockholm/
O=MySQL demo client certificate/
CN=client/emailAddress=client@example.com'</span>
<span class="token operator">AND</span> <span class="token keyword">ISSUER</span> <span class="token string">'/C=SE/ST=Stockholm/L=Stockholm/
O=MySQL/CN=CA/emailAddress=ca@example.com'</span>
<span class="token operator">AND</span> <span class="token keyword">CIPHER</span> <span class="token string">'EDH-RSA-DES-CBC3-SHA'</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="create-user-resource-limits">
</a>
CREATE USER Resource-Limit Options
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045174260912">
</a>
<a class="indexterm" name="idm46045174259424">
</a>
<p>
It is possible to place limits on use of server resources by
an account, as discussed in
<a class="xref" href="user-resources.html" title="8.2.21 Setting Account Resource Limits">
Section 8.2.21, “Setting Account Resource Limits”
</a>
.
To do so, use a
<code class="literal">
WITH
</code>
clause that specifies
one or more
<em class="replaceable">
<code>
resource_option
</code>
</em>
values.
</p>
<p>
Order of
<code class="literal">
WITH
</code>
options does not matter,
except that if a given resource limit is specified multiple
times, the last instance takes precedence.
</p>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
permits these
<em class="replaceable">
<code>
resource_option
</code>
</em>
values:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
MAX_QUERIES_PER_HOUR
<em class="replaceable">
<code>
count
</code>
</em>
</code>
,
<code class="literal">
MAX_UPDATES_PER_HOUR
<em class="replaceable">
<code>
count
</code>
</em>
</code>
,
<code class="literal">
MAX_CONNECTIONS_PER_HOUR
<em class="replaceable">
<code>
count
</code>
</em>
</code>
</p>
<p>
For all accounts named by the statement, these options
restrict how many queries, updates, and connections to the
server are permitted to each account during any given
one-hour period. If
<em class="replaceable">
<code>
count
</code>
</em>
is
<code class="literal">
0
</code>
(the default), this means that there
is no limitation for the account.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MAX_USER_CONNECTIONS
<em class="replaceable">
<code>
count
</code>
</em>
</code>
</p>
<p>
For all accounts named by the statement, restricts the
maximum number of simultaneous connections to the server
by each account. A nonzero
<em class="replaceable">
<code>
count
</code>
</em>
specifies the limit for
the account explicitly. If
<em class="replaceable">
<code>
count
</code>
</em>
is
<code class="literal">
0
</code>
(the default), the server determines the number of
simultaneous connections for the account from the global
value of the
<a class="link" href="server-system-variables.html#sysvar_max_user_connections">
<code class="literal">
max_user_connections
</code>
</a>
system variable. If
<a class="link" href="server-system-variables.html#sysvar_max_user_connections">
<code class="literal">
max_user_connections
</code>
</a>
is
also zero, there is no limit for the account.
</p>
</li>
</ul>
</div>
<p>
Example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa43171150"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">WITH</span> <span class="token keyword">MAX_QUERIES_PER_HOUR</span> <span class="token number">500</span> <span class="token keyword">MAX_UPDATES_PER_HOUR</span> <span class="token number">100</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="create-user-password-management">
</a>
CREATE USER Password-Management Options
</h5>
</div>
</div>
</div>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
supports several
<em class="replaceable">
<code>
password_option
</code>
</em>
values for password
management:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Password expiration options: You can expire an account
password manually and establish its password expiration
policy. Policy options do not expire the password.
Instead, they determine how the server applies automatic
expiration to the account based on password age, which is
assessed from the date and time of the most recent account
password change.
</p>
</li>
<li class="listitem">
<p>
Password reuse options: You can restrict password reuse
based on number of password changes, time elapsed, or
both.
</p>
</li>
<li class="listitem">
<p>
Password verification-required options: You can indicate
whether attempts to change an account password must
specify the current password, as verification that the
user attempting to make the change actually knows the
current password.
</p>
</li>
<li class="listitem">
<p>
Incorrect-password failed-login tracking options: You can
cause the server to track failed login attempts and
temporarily lock accounts for which too many consecutive
incorrect passwords are given. The required number of
failures and the lock time are configurable.
</p>
</li>
</ul>
</div>
<p>
This section describes the syntax for password-management
options. For information about establishing policy for
password management, see
<a class="xref" href="password-management.html" title="8.2.15 Password Management">
Section 8.2.15, “Password Management”
</a>
.
</p>
<p>
If multiple password-management options of a given type are
specified, the last one takes precedence. For example,
<code class="literal">
PASSWORD EXPIRE DEFAULT PASSWORD EXPIRE
NEVER
</code>
is the same as
<code class="literal">
PASSWORD EXPIRE
NEVER
</code>
.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Except for the options that pertain to failed-login
tracking, password-management options apply only to accounts
that use an authentication plugin that stores credentials
internally to MySQL. For accounts that use a plugin that
performs authentication against a credentials system that is
external to MySQL, password management must be handled
externally against that system as well. For more information
about internal credentials storage, see
<a class="xref" href="password-management.html" title="8.2.15 Password Management">
Section 8.2.15, “Password Management”
</a>
.
</p>
</div>
<p>
A client has an expired password if the account password was
expired manually or the password age is considered greater
than its permitted lifetime per the automatic expiration
policy. In this case, the server either disconnects the client
or restricts the operations permitted to it (see
<a class="xref" href="expired-password-handling.html" title="8.2.16 Server Handling of Expired Passwords">
Section 8.2.16, “Server Handling of Expired Passwords”
</a>
). Operations
performed by a restricted client result in an error until the
user establishes a new account password.
</p>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
permits these
<em class="replaceable">
<code>
password_option
</code>
</em>
values for
controlling password expiration:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
PASSWORD EXPIRE
</code>
</p>
<p>
Immediately marks the password expired for all accounts
named by the statement.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa9911708"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
PASSWORD EXPIRE DEFAULT
</code>
</p>
<p>
Sets all accounts named by the statement so that the
global expiration policy applies, as specified by the
<a class="link" href="server-system-variables.html#sysvar_default_password_lifetime">
<code class="literal">
default_password_lifetime
</code>
</a>
system variable.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa34981790"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span> <span class="token keyword">DEFAULT</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
PASSWORD EXPIRE NEVER
</code>
</p>
<p>
This expiration option overrides the global policy for all
accounts named by the statement. For each, it disables
password expiration so that the password never expires.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa24923100"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span> <span class="token keyword">NEVER</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
PASSWORD EXPIRE INTERVAL
<em class="replaceable">
<code>
N
</code>
</em>
DAY
</code>
</p>
<p>
This expiration option overrides the global policy for all
accounts named by the statement. For each, it sets the
password lifetime to
<em class="replaceable">
<code>
N
</code>
</em>
days.
The following statement requires the password to be
changed every 180 days:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa37135344"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">EXPIRE</span> <span class="token keyword">INTERVAL</span> <span class="token number">180</span> <span class="token keyword">DAY</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
permits these
<em class="replaceable">
<code>
password_option
</code>
</em>
values for
controlling reuse of previous passwords based on required
minimum number of password changes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
PASSWORD HISTORY DEFAULT
</code>
</p>
<p>
Sets all accounts named by the statement so that the
global policy about password history length applies, to
prohibit reuse of passwords before the number of changes
specified by the
<a class="link" href="server-system-variables.html#sysvar_password_history">
<code class="literal">
password_history
</code>
</a>
system
variable.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa25053515"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">HISTORY</span> <span class="token keyword">DEFAULT</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
PASSWORD HISTORY
<em class="replaceable">
<code>
N
</code>
</em>
</code>
</p>
<p>
This history-length option overrides the global policy for
all accounts named by the statement. For each, it sets the
password history length to
<em class="replaceable">
<code>
N
</code>
</em>
passwords, to prohibit reusing any of the
<em class="replaceable">
<code>
N
</code>
</em>
most recently chosen
passwords. The following statement prohibits reuse of any
of the previous 6 passwords:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa41220754"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">HISTORY</span> <span class="token number">6</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
permits these
<em class="replaceable">
<code>
password_option
</code>
</em>
values for
controlling reuse of previous passwords based on time elapsed:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
PASSWORD REUSE INTERVAL DEFAULT
</code>
</p>
<p>
Sets all statements named by the account so that the
global policy about time elapsed applies, to prohibit
reuse of passwords newer than the number of days specified
by the
<a class="link" href="server-system-variables.html#sysvar_password_reuse_interval">
<code class="literal">
password_reuse_interval
</code>
</a>
system variable.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa92596386"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REUSE</span> <span class="token keyword">INTERVAL</span> <span class="token keyword">DEFAULT</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
PASSWORD REUSE INTERVAL
<em class="replaceable">
<code>
N
</code>
</em>
DAY
</code>
</p>
<p>
This time-elapsed option overrides the global policy for
all accounts named by the statement. For each, it sets the
password reuse interval to
<em class="replaceable">
<code>
N
</code>
</em>
days, to prohibit reuse of passwords newer than that many
days. The following statement prohibits password reuse for
360 days:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa47044444"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REUSE</span> <span class="token keyword">INTERVAL</span> <span class="token number">360</span> <span class="token keyword">DAY</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
permits these
<em class="replaceable">
<code>
password_option
</code>
</em>
values for
controlling whether attempts to change an account password
must specify the current password, as verification that the
user attempting to make the change actually knows the current
password:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
PASSWORD REQUIRE CURRENT
</code>
</p>
<p>
This verification option overrides the global policy for
all accounts named by the statement. For each, it requires
that password changes specify the current password.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa34842966"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">CURRENT</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
PASSWORD REQUIRE CURRENT OPTIONAL
</code>
</p>
<p>
This verification option overrides the global policy for
all accounts named by the statement. For each, it does not
require that password changes specify the current
password. (The current password may but need not be
given.)
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa35095018"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">CURRENT</span> <span class="token keyword">OPTIONAL</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
PASSWORD REQUIRE CURRENT DEFAULT
</code>
</p>
<p>
Sets all statements named by the account so that the
global policy about password verification applies, as
specified by the
<a class="link" href="server-system-variables.html#sysvar_password_require_current">
<code class="literal">
password_require_current
</code>
</a>
system variable.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa44415253"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">PASSWORD</span> <span class="token keyword">REQUIRE</span> <span class="token keyword">CURRENT</span> <span class="token keyword">DEFAULT</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
permits these
<em class="replaceable">
<code>
password_option
</code>
</em>
values for
controlling failed-login tracking:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
FAILED_LOGIN_ATTEMPTS
<em class="replaceable">
<code>
N
</code>
</em>
</code>
</p>
<p>
Whether to track account login attempts that specify an
incorrect password.
<em class="replaceable">
<code>
N
</code>
</em>
must be a
number from 0 to 32767. A value of 0 disables failed-login
tracking. Values greater than 0 indicate how many
consecutive password failures cause temporary account
locking (if
<code class="literal">
PASSWORD_LOCK_TIME
</code>
is also
nonzero).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
PASSWORD_LOCK_TIME {
<em class="replaceable">
<code>
N
</code>
</em>
| UNBOUNDED}
</code>
</p>
<p>
How long to lock the account after too many consecutive
login attempts provide an incorrect password.
<em class="replaceable">
<code>
N
</code>
</em>
must be a number from 0 to
32767, or
<code class="literal">
UNBOUNDED
</code>
. A value of 0
disables temporary account locking. Values greater than 0
indicate how long to lock the account in days. A value of
<code class="literal">
UNBOUNDED
</code>
causes the account locking
duration to be unbounded; once locked, the account remains
in a locked state until unlocked. For information about
the conditions under which unlocking occurs, see
<a class="xref" href="password-management.html#failed-login-tracking" title="Failed-Login Tracking and Temporary Account Locking">
Failed-Login Tracking and Temporary Account Locking
</a>
.
</p>
</li>
</ul>
</div>
<p>
For failed-login tracking and temporary locking to occur, an
account's
<code class="literal">
FAILED_LOGIN_ATTEMPTS
</code>
and
<code class="literal">
PASSWORD_LOCK_TIME
</code>
options both must be
nonzero. The following statement creates an account that
remains locked for two days after four consecutive password
failures:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa76009571"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">FAILED_LOGIN_ATTEMPTS</span> <span class="token number">4</span> <span class="token keyword">PASSWORD_LOCK_TIME</span> <span class="token number">2</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="create-user-comments-attributes">
</a>
CREATE USER Comment and Attribute Options
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045174154720">
</a>
<a class="indexterm" name="idm46045174153232">
</a>
<p>
You can also include an optional comment or attribute when
creating a user, as described here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<span class="bold">
<strong>
User comment
</strong>
</span>
</p>
<p>
To set a user comment, add
<code class="literal">
COMMENT
'
<em class="replaceable">
<code>
user_comment
</code>
</em>
'
</code>
to the
<code class="literal">
CREATE USER
</code>
statement, where
<em class="replaceable">
<code>
user_comment
</code>
</em>
is the text of the
user comment.
</p>
<p>
Example (omitting any other options):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa47931729"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jon'</span>@<span class="token string">'localhost'</span> <span class="token keyword">COMMENT</span> <span class="token string">'Some information about Jon'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<span class="bold">
<strong>
User attribute
</strong>
</span>
</p>
<p>
A user attribute is a JSON object made up of one or more
key-value pairs, and is set by including
<code class="literal">
ATTRIBUTE
'
<em class="replaceable">
<code>
json_object
</code>
</em>
'
</code>
as part
of
<code class="literal">
CREATE USER
</code>
.
<em class="replaceable">
<code>
json_object
</code>
</em>
must be a valid
JSON object.
</p>
<p>
Example (omitting any other options):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa40889631"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jim'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">ATTRIBUTE</span> <span class="token string">'{"fname": "James", "lname": "Scott", "phone": "123-456-7890"}'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
User comments and user attributes are stored together in the
<code class="literal">
ATTRIBUTE
</code>
column of the Information Schema
<a class="link" href="information-schema-user-attributes-table.html" title="28.3.45 The INFORMATION_SCHEMA USER_ATTRIBUTES Table">
<code class="literal">
USER_ATTRIBUTES
</code>
</a>
table. This query
displays the row in this table inserted by the statement just
shown for creating the user
<code class="literal">
jim@localhost
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa69297191"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>USER_ATTRIBUTES
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> <span class="token keyword">USER</span> <span class="token operator">=</span> <span class="token string">'jim'</span> <span class="token operator">AND</span> <span class="token keyword">HOST</span> <span class="token operator">=</span> <span class="token string">'localhost'</span>\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
USER<span class="token punctuation">:</span> jim
HOST<span class="token punctuation">:</span> localhost
ATTRIBUTE<span class="token punctuation">:</span> {"fname"<span class="token punctuation">:</span> "James", "lname"<span class="token punctuation">:</span> "Scott", "phone"<span class="token punctuation">:</span> "123-456-7890"}
</span><span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
The
<code class="literal">
COMMENT
</code>
option in actuality provides a
shortcut for setting a user attribute whose only element has
<code class="literal">
comment
</code>
as its key and whose value is the
argument supplied for the option. You can see this by
executing the statement
<code class="literal">
CREATE USER 'jon'@'localhost'
COMMENT 'Some information about Jon'
</code>
, and observing
the row which it inserts into the
<a class="link" href="information-schema-user-attributes-table.html" title="28.3.45 The INFORMATION_SCHEMA USER_ATTRIBUTES Table">
<code class="literal">
USER_ATTRIBUTES
</code>
</a>
table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44230922"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'jon'</span>@<span class="token string">'localhost'</span> <span class="token keyword">COMMENT</span> <span class="token string">'Some information about Jon'</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.06 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>USER_ATTRIBUTES
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> <span class="token keyword">USER</span> <span class="token operator">=</span> <span class="token string">'jon'</span> <span class="token operator">AND</span> <span class="token keyword">HOST</span> <span class="token operator">=</span> <span class="token string">'localhost'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> USER <span class="token punctuation">|</span> HOST <span class="token punctuation">|</span> ATTRIBUTE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> jon <span class="token punctuation">|</span> localhost <span class="token punctuation">|</span> {"comment": "Some information about Jon"} <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
You cannot use
<code class="literal">
COMMENT
</code>
and
<code class="literal">
ATTRIBUTE
</code>
together in the same
<code class="literal">
CREATE USER
</code>
statement; attempting to do so
causes a syntax error. To set a user comment concurrently with
setting a user attribute, use
<code class="literal">
ATTRIBUTE
</code>
and
include in its argument a value with a
<code class="literal">
comment
</code>
key, like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa24248100"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'bill'</span>@<span class="token string">'localhost'</span>
<span class="token prompt"> -></span> <span class="token keyword">ATTRIBUTE</span> <span class="token string">'{"fname":"William", "lname":"Schmidt",
-> "comment":"Website developer"}'</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.16 sec)</span></code></pre>
</div>
<p>
Since the content of the
<code class="literal">
ATTRIBUTE
</code>
row is a
JSON object, you can employ any appropriate MySQL JSON
functions or operators to manipulate it, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa89391717"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span>
<span class="token prompt"> -></span> <span class="token keyword">USER</span> <span class="token keyword">AS</span> <span class="token keyword">User</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">HOST</span> <span class="token keyword">AS</span> <span class="token keyword">Host</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token function">CONCAT</span><span class="token punctuation">(</span><span class="token keyword">ATTRIBUTE</span><span class="token operator">-</span><span class="token operator">>></span><span class="token string">"$.fname"</span><span class="token punctuation">,</span><span class="token string">" "</span><span class="token punctuation">,</span><span class="token keyword">ATTRIBUTE</span><span class="token operator">-</span><span class="token operator">>></span><span class="token string">"$.lname"</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> <span class="token string">'Full Name'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">ATTRIBUTE</span><span class="token operator">-</span><span class="token operator">>></span><span class="token string">"$.comment"</span> <span class="token keyword">AS</span> <span class="token keyword">Comment</span>
<span class="token prompt"> -></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>USER_ATTRIBUTES
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> <span class="token keyword">USER</span><span class="token operator">=</span><span class="token string">'bill'</span> <span class="token operator">AND</span> <span class="token keyword">HOST</span><span class="token operator">=</span><span class="token string">'localhost'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> User <span class="token punctuation">|</span> Host <span class="token punctuation">|</span> Full Name <span class="token punctuation">|</span> Comment <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> bill <span class="token punctuation">|</span> localhost <span class="token punctuation">|</span> William Schmidt <span class="token punctuation">|</span> Website developer <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
To set or to make changes in the user comment or user
attribute for an existing user, you can use a
<code class="literal">
COMMENT
</code>
or
<code class="literal">
ATTRIBUTE
</code>
option with an
<a class="link" href="alter-user.html" title="15.7.1.1 ALTER USER Statement">
<code class="literal">
ALTER USER
</code>
</a>
statement.
</p>
<p>
Because the user comment and user attribute are stored
together internally in a single
<a class="link" href="json.html" title="13.5 The JSON Data Type">
<code class="literal">
JSON
</code>
</a>
column, this sets an upper
limit on their maximum combined size; see
<a class="xref" href="storage-requirements.html#data-types-storage-reqs-json" title="JSON Storage Requirements">
JSON Storage Requirements
</a>
, for more
information.
</p>
<p>
See also the description of the Information Schema
<a class="link" href="information-schema-user-attributes-table.html" title="28.3.45 The INFORMATION_SCHEMA USER_ATTRIBUTES Table">
<code class="literal">
USER_ATTRIBUTES
</code>
</a>
table for more
information and examples.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="create-user-account-locking">
</a>
CREATE USER Account-Locking Options
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045174103360">
</a>
<p>
MySQL supports account locking and unlocking using the
<code class="literal">
ACCOUNT LOCK
</code>
and
<code class="literal">
ACCOUNT
UNLOCK
</code>
options, which specify the locking state for
an account. For additional discussion, see
<a class="xref" href="account-locking.html" title="8.2.20 Account Locking">
Section 8.2.20, “Account Locking”
</a>
.
</p>
<p>
If multiple account-locking options are specified, the last
one takes precedence.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="create-user-binary-logging">
</a>
CREATE USER Binary Logging
</h5>
</div>
</div>
</div>
<a class="indexterm" name="idm46045174097376">
</a>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
is written to the
binary log if it succeeds, but not if it fails; in that case,
rollback occurs and no changes are made. A statement written
to the binary log includes all named users. If the
<code class="literal">
IF
NOT EXISTS
</code>
clause is given, this includes even users
that already exist and were not created.
</p>
<p>
The statement written to the binary log specifies an
authentication plugin for each user, determined as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The plugin named in the original statement, if one was
specified.
</p>
</li>
<li class="listitem">
<p>
Otherwise, the default authentication plugin. In
particular, if a user
<code class="literal">
u1
</code>
already exists
and uses a nondefault authentication plugin, the statement
written to the binary log for
<code class="literal">
CREATE USER IF NOT
EXISTS u1
</code>
names the default authentication
plugin. (If the statement written to the binary log must
specify a nondefault authentication plugin for a user,
include it in the original statement.)
</p>
</li>
</ul>
</div>
<p>
If the server adds the default authentication plugin for any
nonexisting users in the statement written to the binary log,
it writes a warning to the error log naming those users.
</p>
<p>
If the original statement specifies the
<code class="literal">
FAILED_LOGIN_ATTEMPTS
</code>
or
<code class="literal">
PASSWORD_LOCK_TIME
</code>
option, the statement
written to the binary log includes the option.
</p>
<p>
<a class="link" href="create-user.html" title="15.7.1.3 CREATE USER Statement">
<code class="literal">
CREATE USER
</code>
</a>
statements with
clauses that support multifactor authentication (MFA) are
written to the binary log.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
CREATE USER ... IDENTIFIED WITH .. INITIAL
AUTHENTICATION IDENTIFIED WITH ...
</code>
statements
are written to the binary log as
<code class="literal">
CREATE USER ..
IDENTIFIED WITH .. INITIAL AUTHENTICATION IDENTIFIED WITH
.. AS
'
<em class="replaceable">
<code>
password-hash
</code>
</em>
'
</code>
,
where the
<em class="replaceable">
<code>
password-hash
</code>
</em>
is the
user-specified
<em class="replaceable">
<code>
auth-string
</code>
</em>
or
the random password generated by server when the
<code class="literal">
RANDOM PASSWORD
</code>
clause is specified.
</p>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/file-permissions.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="file-permissions">
</a>
B.3.3.1 Problems with File Permissions
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045054131008">
</a>
<a class="indexterm" name="idm46045054129552">
</a>
<a class="indexterm" name="idm46045054128064">
</a>
<a class="indexterm" name="idm46045054126576">
</a>
<a class="indexterm" name="idm46045054125488">
</a>
<p>
If you have problems with file permissions, the
<code class="literal">
UMASK
</code>
or
<code class="literal">
UMASK_DIR
</code>
environment variable might be set incorrectly when
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
starts. For example,
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
might issue the following error
message when you create a table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-none"><div class="docs-select-all right" id="sa5454200"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">ERROR: Can't find file: 'path/with/<em class="replaceable">file_name</em>' (Errcode: 13)</code></pre>
</div>
<p>
The default
<code class="literal">
UMASK
</code>
and
<code class="literal">
UMASK_DIR
</code>
values are
<code class="literal">
0640
</code>
and
<code class="literal">
0750
</code>
,
respectively.
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
assumes that the value
for
<code class="literal">
UMASK
</code>
or
<code class="literal">
UMASK_DIR
</code>
is in octal if it starts with a zero. For example, setting
<code class="literal">
UMASK=0600
</code>
is equivalent to
<code class="literal">
UMASK=384
</code>
because 0600 octal is 384
decimal.
</p>
<p>
Assuming that you start
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
using
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
, change the default
<code class="literal">
UMASK
</code>
value as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa58372211"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">UMASK<span class="token attr-value"><span class="token punctuation">=</span>384</span> <span class="token comment" spellcheck="true"># = 600 in octal</span>
export UMASK
mysqld_safe &</code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
An exception applies for the error log file if you start
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
using
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
, which does not respect
<code class="literal">
UMASK
</code>
:
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
may
create the error log file if it does not exist prior to
starting
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
, and
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
uses a umask set to a strict
value of
<code class="literal">
0137
</code>
. If this is unsuitable,
create the error file manually with the desired access mode
prior to executing
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
.
</p>
</div>
<a class="indexterm" name="idm46045054095904">
</a>
<a class="indexterm" name="idm46045054094816">
</a>
<p>
By default,
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
creates database
directories with an access permission value of
<code class="literal">
0750
</code>
. To modify this behavior, set the
<code class="literal">
UMASK_DIR
</code>
variable. If you set its value,
new directories are created with the combined
<code class="literal">
UMASK
</code>
and
<code class="literal">
UMASK_DIR
</code>
values. For example, to give group access to all new
directories, start
<a class="link" href="mysqld-safe.html" title="6.3.2 mysqld_safe — MySQL Server Startup Script">
<span class="command">
<strong>
mysqld_safe
</strong>
</span>
</a>
as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa64823857"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">UMASK_DIR<span class="token attr-value"><span class="token punctuation">=</span>504</span> <span class="token comment" spellcheck="true"># = 770 in octal</span>
export UMASK_DIR
mysqld_safe &</code></pre>
</div>
<p>
For additional details, see
<a class="xref" href="environment-variables.html" title="6.9 Environment Variables">
Section 6.9, “Environment Variables”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/commands-out-of-sync.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="commands-out-of-sync">
</a>
B.3.2.12 Commands out of sync
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045054234720">
</a>
<p>
If you get
<code class="literal">
Commands out of sync; you can't run this
command now
</code>
in your client code, you are calling
client functions in the wrong order.
</p>
<p>
This can happen, for example, if you are using
<a class="ulink" href="/doc/c-api/8.4/en/mysql-use-result.html" target="_top">
<code class="literal">
mysql_use_result()
</code>
</a>
and try to
execute a new query before you have called
<a class="ulink" href="/doc/c-api/8.4/en/mysql-free-result.html" target="_top">
<code class="literal">
mysql_free_result()
</code>
</a>
. It can
also happen if you try to execute two queries that return data
without calling
<a class="ulink" href="/doc/c-api/8.4/en/mysql-use-result.html" target="_top">
<code class="literal">
mysql_use_result()
</code>
</a>
or
<a class="ulink" href="/doc/c-api/8.4/en/mysql-store-result.html" target="_top">
<code class="literal">
mysql_store_result()
</code>
</a>
in
between.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-rbr-safe-unsafe.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-rbr-safe-unsafe">
</a>
19.2.1.3 Determination of Safe and Unsafe Statements in Binary Logging
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045138307408">
</a>
<a class="indexterm" name="idm46045138305952">
</a>
<a class="indexterm" name="idm46045138304448">
</a>
<p>
The
<span class="quote">
“
<span class="quote">
safeness
</span>
”
</span>
of a statement in MySQL replication
refers to whether the statement and its effects can be
replicated correctly using statement-based format. If this is
true of the statement, we refer to the statement as
<span class="firstterm">
safe
</span>
; otherwise, we refer
to it as
<span class="firstterm">
unsafe
</span>
.
</p>
<p>
In general, a statement is safe if it deterministic, and unsafe
if it is not. However, certain nondeterministic functions are
<span class="emphasis">
<em>
not
</em>
</span>
considered unsafe (see
<a class="xref" href="replication-rbr-safe-unsafe.html#replication-rbr-safe-unsafe-not" title="Nondeterministic functions not considered unsafe">
Nondeterministic functions not considered unsafe
</a>
, later in this
section). In addition, statements using results from
floating-point math functions—which are
hardware-dependent—are always considered unsafe (see
<a class="xref" href="replication-features-floatvalues.html" title="19.5.1.12 Replication and Floating-Point Values">
Section 19.5.1.12, “Replication and Floating-Point Values”
</a>
).
</p>
<p>
<b>
Handling of safe and unsafe statements.
</b>
A statement is treated differently depending on whether the
statement is considered safe, and with respect to the binary
logging format (that is, the current value of
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
).
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
When using row-based logging, no distinction is made in the
treatment of safe and unsafe statements.
</p>
</li>
<li class="listitem">
<p>
When using mixed-format logging, statements flagged as
unsafe are logged using the row-based format; statements
regarded as safe are logged using the statement-based
format.
</p>
</li>
<li class="listitem">
<p>
When using statement-based logging, statements flagged as
being unsafe generate a warning to this effect. Safe
statements are logged normally.
</p>
</li>
</ul>
</div>
<p>
Each statement flagged as unsafe generates a warning. If a large
number of such statements were executed on the source, this
could lead to excessively large error log files. To prevent
this, MySQL has a warning suppression mechanism. Whenever the 50
most recent
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_binlog_unsafe_statement" target="_top">
<code class="literal">
ER_BINLOG_UNSAFE_STATEMENT
</code>
</a>
warnings have been generated more than 50 times in any 50-second
period, warning suppression is enabled. When activated, this
causes such warnings not to be written to the error log;
instead, for each 50 warnings of this type, a note
<code class="literal">
The
last warning was repeated
<em class="replaceable">
<code>
N
</code>
</em>
times in
last
<em class="replaceable">
<code>
S
</code>
</em>
seconds
</code>
is written
to the error log. This continues as long as the 50 most recent
such warnings were issued in 50 seconds or less; once the rate
has decreased below this threshold, the warnings are once again
logged normally. Warning suppression has no effect on how the
safety of statements for statement-based logging is determined,
nor on how warnings are sent to the client. MySQL clients still
receive one warning for each such statement.
</p>
<p>
For more information, see
<a class="xref" href="replication-formats.html" title="19.2.1 Replication Formats">
Section 19.2.1, “Replication Formats”
</a>
.
</p>
<p>
<b>
Statements considered unsafe.
</b>
<a class="indexterm" name="idm46045138284880">
</a>
Statements with the following characteristics are considered
unsafe:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<b>
Statements containing system functions that may return a different value
on the replica.
</b>
These functions include
<a class="link" href="information-functions.html#function_found-rows">
<code class="literal">
FOUND_ROWS()
</code>
</a>
,
<a class="link" href="locking-functions.html#function_get-lock">
<code class="literal">
GET_LOCK()
</code>
</a>
,
<a class="link" href="locking-functions.html#function_is-free-lock">
<code class="literal">
IS_FREE_LOCK()
</code>
</a>
,
<a class="link" href="locking-functions.html#function_is-used-lock">
<code class="literal">
IS_USED_LOCK()
</code>
</a>
,
<a class="link" href="string-functions.html#function_load-file">
<code class="literal">
LOAD_FILE()
</code>
</a>
,
<a class="link" href="mathematical-functions.html#function_rand">
<code class="literal">
RAND()
</code>
</a>
,
<a class="link" href="locking-functions.html#function_release-lock">
<code class="literal">
RELEASE_LOCK()
</code>
</a>
,
<a class="link" href="information-functions.html#function_row-count">
<code class="literal">
ROW_COUNT()
</code>
</a>
,
<a class="link" href="information-functions.html#function_session-user">
<code class="literal">
SESSION_USER()
</code>
</a>
,
<a class="link" href="miscellaneous-functions.html#function_sleep">
<code class="literal">
SLEEP()
</code>
</a>
,
<a class="link" href="replication-functions-synchronization.html#function_source-pos-wait">
<code class="literal">
SOURCE_POS_WAIT()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_sysdate">
<code class="literal">
SYSDATE()
</code>
</a>
,
<a class="link" href="information-functions.html#function_system-user">
<code class="literal">
SYSTEM_USER()
</code>
</a>
,
<a class="link" href="information-functions.html#function_user">
<code class="literal">
USER()
</code>
</a>
,
<a class="link" href="miscellaneous-functions.html#function_uuid">
<code class="literal">
UUID()
</code>
</a>
, and
<a class="link" href="miscellaneous-functions.html#function_uuid-short">
<code class="literal">
UUID_SHORT()
</code>
</a>
.
</p>
<p>
<a name="replication-rbr-safe-unsafe-not">
</a>
<b>
Nondeterministic functions not considered unsafe.
</b>
Although these functions are not deterministic, they are
treated as safe for purposes of logging and replication:
<a class="link" href="information-functions.html#function_connection-id">
<code class="literal">
CONNECTION_ID()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_curdate">
<code class="literal">
CURDATE()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_current-date">
<code class="literal">
CURRENT_DATE()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_current-time">
<code class="literal">
CURRENT_TIME()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_current-timestamp">
<code class="literal">
CURRENT_TIMESTAMP()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_curtime">
<code class="literal">
CURTIME()
</code>
</a>
,
<a class="link" href="information-functions.html#function_last-insert-id">
<code class="literal">
LAST_INSERT_ID()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_localtime">
<code class="literal">
LOCALTIME()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_localtimestamp">
<code class="literal">
LOCALTIMESTAMP()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_now">
<code class="literal">
NOW()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_unix-timestamp">
<code class="literal">
UNIX_TIMESTAMP()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_utc-date">
<code class="literal">
UTC_DATE()
</code>
</a>
,
<a class="link" href="date-and-time-functions.html#function_utc-time">
<code class="literal">
UTC_TIME()
</code>
</a>
, and
<a class="link" href="date-and-time-functions.html#function_utc-timestamp">
<code class="literal">
UTC_TIMESTAMP()
</code>
</a>
.
</p>
<p>
For more information, see
<a class="xref" href="replication-features-functions.html" title="19.5.1.14 Replication and System Functions">
Section 19.5.1.14, “Replication and System Functions”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<b>
References to system variables.
</b>
Most system variables are not replicated correctly using
the statement-based format. See
<a class="xref" href="replication-features-variables.html" title="19.5.1.39 Replication and Variables">
Section 19.5.1.39, “Replication and Variables”
</a>
. For
exceptions, see
<a class="xref" href="binary-log-mixed.html" title="7.4.4.3 Mixed Binary Logging Format">
Section 7.4.4.3, “Mixed Binary Logging Format”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<b>
Loadable Functions.
</b>
Since we have no control over what a loadable function
does, we must assume that it is executing unsafe
statements.
</p>
</li>
<li class="listitem">
<p>
<b>
Fulltext plugin.
</b>
This plugin may behave differently on different MySQL
servers; therefore, statements depending on it could have
different results. For this reason, all statements relying
on the fulltext plugin are treated as unsafe in MySQL.
</p>
</li>
<li class="listitem">
<p>
<b>
Trigger or stored program updates a table having an AUTO_INCREMENT
column.
</b>
This is unsafe because the order in which the rows are
updated may differ on the source and the replica.
</p>
<p>
In addition, an
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
into a
table that has a composite primary key containing an
<code class="literal">
AUTO_INCREMENT
</code>
column that is not the
first column of this composite key is unsafe.
</p>
<p>
For more information, see
<a class="xref" href="replication-features-auto-increment.html" title="19.5.1.1 Replication and AUTO_INCREMENT">
Section 19.5.1.1, “Replication and AUTO_INCREMENT”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<b>
INSERT ... ON DUPLICATE KEY UPDATE statements on tables with multiple
primary or unique keys.
</b>
When executed against a table that contains more than one
primary or unique key, this statement is considered
unsafe, being sensitive to the order in which the storage
engine checks the keys, which is not deterministic, and on
which the choice of rows updated by the MySQL Server
depends.
</p>
<p>
An
<a class="link" href="insert-on-duplicate.html" title="15.2.7.2 INSERT ... ON DUPLICATE KEY UPDATE Statement">
<code class="literal">
INSERT
... ON DUPLICATE KEY UPDATE
</code>
</a>
statement against a
table having more than one unique or primary key is marked
as unsafe for statement-based replication. (Bug #11765650,
Bug #58637)
</p>
</li>
<li class="listitem">
<p>
<b>
Updates using LIMIT.
</b>
The order in which rows are retrieved is not specified,
and is therefore considered unsafe. See
<a class="xref" href="replication-features-limit.html" title="19.5.1.18 Replication and LIMIT">
Section 19.5.1.18, “Replication and LIMIT”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<b>
Accesses or references log tables.
</b>
The contents of the system log table may differ between
source and replica.
</p>
</li>
<li class="listitem">
<p>
<b>
Nontransactional operations after transactional operations.
</b>
Within a transaction, allowing any nontransactional reads
or writes to execute after any transactional reads or
writes is considered unsafe.
</p>
<p>
For more information, see
<a class="xref" href="replication-features-transactions.html" title="19.5.1.35 Replication and Transactions">
Section 19.5.1.35, “Replication and Transactions”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<b>
Accesses or references self-logging tables.
</b>
All reads and writes to self-logging tables are considered
unsafe. Within a transaction, any statement following a
read or write to self-logging tables is also considered
unsafe.
</p>
</li>
<li class="listitem">
<p>
<b>
LOAD DATA statements.
</b>
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD DATA
</code>
</a>
is treated as
unsafe and when
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=MIXED
</code>
</a>
the
statement is logged in row-based format. When
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=STATEMENT
</code>
</a>
<a class="link" href="load-data.html" title="15.2.9 LOAD DATA Statement">
<code class="literal">
LOAD DATA
</code>
</a>
does not generate
a warning, unlike other unsafe statements.
</p>
</li>
<li class="listitem">
<p>
<b>
XA transactions.
</b>
If two XA transactions committed in parallel on the source
are being prepared on the replica in the inverse order,
locking dependencies can occur with statement-based
replication that cannot be safely resolved, and it is
possible for replication to fail with deadlock on the
replica. When
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=STATEMENT
</code>
</a>
is set, DML statements inside XA transactions are flagged
as being unsafe and generate a warning. When
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=MIXED
</code>
</a>
or
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format=ROW
</code>
</a>
is set,
DML statements inside XA transactions are logged using
row-based replication, and the potential issue is not
present.
</p>
</li>
<li class="listitem">
<p>
<b>
<code class="literal">
DEFAULT
</code>
clause that refers to a nondeterministic
function.
</b>
If an expression default value refers to a
nondeterministic function, any statement that causes the
expression to be evaluated is unsafe for statement-based
replication. This includes statements such as
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
,
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
, and
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
. Unlike most
other unsafe statements, this category of statement cannot
be replicated safely in row-based format. When
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
is set to
<code class="literal">
STATEMENT
</code>
, the statement is logged and
executed but a warning message is written to the error
log. When
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
is set to
<code class="literal">
MIXED
</code>
or
<code class="literal">
ROW
</code>
, the statement is not executed and
an error message is written to the error log. For more
information on the handling of explicit defaults, see
<a class="xref" href="data-type-defaults.html#data-type-defaults-explicit" title="Explicit Default Handling">
Explicit Default Handling
</a>
.
</p>
</li>
</ul>
</div>
<p>
For additional information, see
<a class="xref" href="replication-features.html" title="19.5.1 Replication Features and Issues">
Section 19.5.1, “Replication Features and Issues”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/data-masking-components.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="data-masking-components">
</a>
8.5.2 MySQL Enterprise Data Masking and De-Identification Components
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="data-masking-components-installation.html">
8.5.2.1 MySQL Enterprise Data Masking and De-Identification Component Installation
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-masking-component-usage.html">
8.5.2.2 Using MySQL Enterprise Data Masking and De-Identification Components
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-masking-component-function-reference.html">
8.5.2.3 MySQL Enterprise Data Masking and De-Identification Component Function Reference
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-masking-component-functions.html">
8.5.2.4 MySQL Enterprise Data Masking and De-Identification Component Function Descriptions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="data-masking-component-variables.html">
8.5.2.5 MySQL Enterprise Data Masking and De-Identification Component Variables
</a>
</span>
</dt>
</dl>
</div>
<p>
MySQL Enterprise Data Masking and De-Identification implements these elements:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A table for persistent storage of dictionaries and terms.
</p>
</li>
<li class="listitem">
<p>
A component named
<code class="literal">
component_masking
</code>
that
implements masking functionality and exposes it as service
interface for developers.
</p>
<p>
Developers who wish to incorporate the same service functions
used by
<code class="literal">
component_masking
</code>
should consult
the
<code class="filename">
internal\components\masking\component_masking.h
</code>
file in a MySQL source distribution or
https://dev.mysql.com/doc/dev/mysql-server/latest.
</p>
</li>
<li class="listitem">
<p>
A component named
<code class="literal">
component_masking_functions
</code>
that provides
loadable functions.
</p>
<p>
The set of loadable functions enables an SQL-level API for
performing masking and de-identification operations. Some of
the functions require the
<a class="link" href="privileges-provided.html#priv_masking-dictionaries-admin">
<code class="literal">
MASKING_DICTIONARIES_ADMIN
</code>
</a>
dynamic privilege.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/expressions.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="expressions">
</a>
11.5 Expressions
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045218613088">
</a>
<p>
This section lists the grammar rules that expressions must follow
in MySQL and provides additional information about the types of
terms that may appear in expressions.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="expressions.html#expression-syntax" title="Expression Syntax">
Expression Syntax
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="expressions.html#expression-term-notes" title="Expression Term Notes">
Expression Term Notes
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="expressions.html#temporal-intervals" title="Temporal Intervals">
Temporal Intervals
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="expression-syntax">
</a>
Expression Syntax
</h3>
</div>
</div>
</div>
<p>
The following grammar rules define expression syntax in MySQL.
The grammar shown here is based on that given in the
<code class="filename">
sql/sql_yacc.yy
</code>
file of MySQL source
distributions. For additional information about some of the
expression terms, see
<a class="xref" href="expressions.html#expression-term-notes" title="Expression Term Notes">
Expression Term Notes
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa22441447"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><em class="replaceable">expr</em>:
<em class="replaceable">expr</em> <span class="token operator">OR</span> <em class="replaceable">expr</em>
<span class="token operator">|</span> <em class="replaceable">expr</em> <span class="token operator">||</span> <em class="replaceable">expr</em>
<span class="token operator">|</span> <em class="replaceable">expr</em> <span class="token keyword">XOR</span> <em class="replaceable">expr</em>
<span class="token operator">|</span> <em class="replaceable">expr</em> <span class="token operator">AND</span> <em class="replaceable">expr</em>
<span class="token operator">|</span> <em class="replaceable">expr</em> <span class="token operator">&&</span> <em class="replaceable">expr</em>
<span class="token operator">|</span> <span class="token operator">NOT</span> <em class="replaceable">expr</em>
<span class="token operator">|</span> <span class="token operator">!</span> <em class="replaceable">expr</em>
<span class="token operator">|</span> <em class="replaceable">boolean_primary</em> <span class="token operator">IS</span> <span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> {<span class="token boolean">TRUE</span> <span class="token operator">|</span> <span class="token boolean">FALSE</span> <span class="token operator">|</span> <span class="token keyword">UNKNOWN</span>}
<span class="token operator">|</span> <em class="replaceable">boolean_primary</em>
<em class="replaceable">boolean_primary</em>:
<em class="replaceable">boolean_primary</em> <span class="token operator">IS</span> <span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> <span class="token boolean">NULL</span>
<span class="token operator">|</span> <em class="replaceable">boolean_primary</em> <span class="token operator"><=></span> <em class="replaceable">predicate</em>
<span class="token operator">|</span> <em class="replaceable">boolean_primary</em> <em class="replaceable">comparison_operator</em> <em class="replaceable">predicate</em>
<span class="token operator">|</span> <em class="replaceable">boolean_primary</em> <em class="replaceable">comparison_operator</em> {<span class="token keyword">ALL</span> <span class="token operator">|</span> <span class="token keyword">ANY</span>} <span class="token punctuation">(</span><em class="replaceable">subquery</em><span class="token punctuation">)</span>
<span class="token operator">|</span> <em class="replaceable">predicate</em>
<em class="replaceable">comparison_operator</em>: <span class="token operator">=</span> <span class="token operator">|</span> <span class="token operator">>=</span> <span class="token operator">|</span> <span class="token operator">></span> <span class="token operator">|</span> <span class="token operator"><=</span> <span class="token operator">|</span> <span class="token operator"><</span> <span class="token operator">|</span> <span class="token operator"><></span> <span class="token operator">|</span> <span class="token operator">!=</span>
<em class="replaceable">predicate</em>:
<em class="replaceable">bit_expr</em> <span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> <span class="token keyword">IN</span> <span class="token punctuation">(</span><em class="replaceable">subquery</em><span class="token punctuation">)</span>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> <span class="token keyword">IN</span> <span class="token punctuation">(</span><em class="replaceable">expr</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">expr</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> <span class="token operator">BETWEEN</span> <em class="replaceable">bit_expr</em> <span class="token operator">AND</span> <em class="replaceable">predicate</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token keyword">SOUNDS</span> <span class="token operator">LIKE</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> <span class="token operator">LIKE</span> <em class="replaceable">simple_expr</em> <span class="token punctuation">[</span><span class="token keyword">ESCAPE</span> <em class="replaceable">simple_expr</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> <span class="token operator">REGEXP</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em>
<em class="replaceable">bit_expr</em>:
<em class="replaceable">bit_expr</em> <span class="token operator">|</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">&</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator"><<</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">>></span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">+</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">-</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">*</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">/</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">DIV</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">MOD</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">%</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">^</span> <em class="replaceable">bit_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">+</span> <em class="replaceable">interval_expr</em>
<span class="token operator">|</span> <em class="replaceable">bit_expr</em> <span class="token operator">-</span> <em class="replaceable">interval_expr</em>
<span class="token operator">|</span> <em class="replaceable">simple_expr</em>
<em class="replaceable">simple_expr</em>:
<em class="replaceable">literal</em>
<span class="token operator">|</span> <em class="replaceable">identifier</em>
<span class="token operator">|</span> <em class="replaceable">function_call</em>
<span class="token operator">|</span> <em class="replaceable">simple_expr</em> <span class="token keyword">COLLATE</span> <em class="replaceable">collation_name</em>
<span class="token operator">|</span> <em class="replaceable">param_marker</em>
<span class="token operator">|</span> <em class="replaceable">variable</em>
<span class="token operator">|</span> <em class="replaceable">simple_expr</em> <span class="token operator">||</span> <em class="replaceable">simple_expr</em>
<span class="token operator">|</span> <span class="token operator">+</span> <em class="replaceable">simple_expr</em>
<span class="token operator">|</span> <span class="token operator">-</span> <em class="replaceable">simple_expr</em>
<span class="token operator">|</span> <span class="token operator">~</span> <em class="replaceable">simple_expr</em>
<span class="token operator">|</span> <span class="token operator">!</span> <em class="replaceable">simple_expr</em>
<span class="token operator">|</span> <span class="token datatype">BINARY</span> <em class="replaceable">simple_expr</em>
<span class="token operator">|</span> <span class="token punctuation">(</span><em class="replaceable">expr</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">expr</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span>
<span class="token operator">|</span> <span class="token keyword">ROW</span> <span class="token punctuation">(</span><em class="replaceable">expr</em><span class="token punctuation">,</span> <em class="replaceable">expr</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">expr</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span>
<span class="token operator">|</span> <span class="token punctuation">(</span><em class="replaceable">subquery</em><span class="token punctuation">)</span>
<span class="token operator">|</span> <span class="token keyword">EXISTS</span> <span class="token punctuation">(</span><em class="replaceable">subquery</em><span class="token punctuation">)</span>
<span class="token operator">|</span> {<em class="replaceable">identifier</em> <em class="replaceable">expr</em>}
<span class="token operator">|</span> <em class="replaceable">match_expr</em>
<span class="token operator">|</span> <em class="replaceable">case_expr</em>
<span class="token operator">|</span> <em class="replaceable">interval_expr</em></code></pre>
</div>
<p>
For operator precedence, see
<a class="xref" href="operator-precedence.html" title="14.4.1 Operator Precedence">
Section 14.4.1, “Operator Precedence”
</a>
. The precedence and
meaning of some operators depends on the SQL mode:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
By default,
<a class="link" href="logical-operators.html#operator_or">
<code class="literal">
||
</code>
</a>
is a logical
<a class="link" href="logical-operators.html#operator_or">
<code class="literal">
OR
</code>
</a>
operator. With
<a class="link" href="sql-mode.html#sqlmode_pipes_as_concat">
<code class="literal">
PIPES_AS_CONCAT
</code>
</a>
enabled,
<a class="link" href="logical-operators.html#operator_or">
<code class="literal">
||
</code>
</a>
is string
concatenation, with a precedence between
<a class="link" href="bit-functions.html#operator_bitwise-xor">
<code class="literal">
^
</code>
</a>
and
the unary operators.
</p>
</li>
<li class="listitem">
<p>
By default,
<a class="link" href="logical-operators.html#operator_not">
<code class="literal">
!
</code>
</a>
has a higher precedence than
<code class="literal">
NOT
</code>
. With
<a class="link" href="sql-mode.html#sqlmode_high_not_precedence">
<code class="literal">
HIGH_NOT_PRECEDENCE
</code>
</a>
enabled,
<a class="link" href="logical-operators.html#operator_not">
<code class="literal">
!
</code>
</a>
and
<code class="literal">
NOT
</code>
have the same precedence.
</p>
</li>
</ul>
</div>
<p>
See
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="expression-term-notes">
</a>
Expression Term Notes
</h3>
</div>
</div>
</div>
<p>
For literal value syntax, see
<a class="xref" href="literals.html" title="11.1 Literal Values">
Section 11.1, “Literal Values”
</a>
.
</p>
<p>
For identifier syntax, see
<a class="xref" href="identifiers.html" title="11.2 Schema Object Names">
Section 11.2, “Schema Object Names”
</a>
.
</p>
<p>
Variables can be user variables, system variables, or stored
program local variables or parameters:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
User variables:
<a class="xref" href="user-variables.html" title="11.4 User-Defined Variables">
Section 11.4, “User-Defined Variables”
</a>
</p>
</li>
<li class="listitem">
<p>
System variables:
<a class="xref" href="using-system-variables.html" title="7.1.9 Using System Variables">
Section 7.1.9, “Using System Variables”
</a>
</p>
</li>
<li class="listitem">
<p>
Stored program local variables:
<a class="xref" href="declare-local-variable.html" title="15.6.4.1 Local Variable DECLARE Statement">
Section 15.6.4.1, “Local Variable DECLARE Statement”
</a>
</p>
</li>
<li class="listitem">
<p>
Stored program parameters:
<a class="xref" href="create-procedure.html" title="15.1.17 CREATE PROCEDURE and CREATE FUNCTION Statements">
Section 15.1.17, “CREATE PROCEDURE and CREATE FUNCTION Statements”
</a>
</p>
</li>
</ul>
</div>
<p>
<em class="replaceable">
<code>
param_marker
</code>
</em>
is
<code class="literal">
?
</code>
as used in prepared statements for placeholders. See
<a class="xref" href="prepare.html" title="15.5.1 PREPARE Statement">
Section 15.5.1, “PREPARE Statement”
</a>
.
</p>
<p>
<code class="literal">
(
<em class="replaceable">
<code>
subquery
</code>
</em>
)
</code>
indicates a subquery that returns a single value; that is, a
scalar subquery. See
<a class="xref" href="scalar-subqueries.html" title="15.2.15.1 The Subquery as Scalar Operand">
Section 15.2.15.1, “The Subquery as Scalar Operand”
</a>
.
</p>
<p>
<code class="literal">
{
<em class="replaceable">
<code>
identifier
</code>
</em>
<em class="replaceable">
<code>
expr
</code>
</em>
}
</code>
is ODBC escape syntax
and is accepted for ODBC compatibility. The value is
<em class="replaceable">
<code>
expr
</code>
</em>
. The
<code class="literal">
{
</code>
and
<code class="literal">
}
</code>
curly braces in the syntax should be
written literally; they are not metasyntax as used elsewhere in
syntax descriptions.
</p>
<p>
<em class="replaceable">
<code>
match_expr
</code>
</em>
indicates a
<a class="link" href="fulltext-search.html#function_match">
<code class="literal">
MATCH
</code>
</a>
expression. See
<a class="xref" href="fulltext-search.html" title="14.9 Full-Text Search Functions">
Section 14.9, “Full-Text Search Functions”
</a>
.
</p>
<p>
<em class="replaceable">
<code>
case_expr
</code>
</em>
indicates a
<a class="link" href="flow-control-functions.html#operator_case">
<code class="literal">
CASE
</code>
</a>
expression. See
<a class="xref" href="flow-control-functions.html" title="14.5 Flow Control Functions">
Section 14.5, “Flow Control Functions”
</a>
.
</p>
<p>
<em class="replaceable">
<code>
interval_expr
</code>
</em>
represents a temporal
interval. See
<a class="xref" href="expressions.html#temporal-intervals" title="Temporal Intervals">
Temporal Intervals
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="temporal-intervals">
</a>
Temporal Intervals
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045218514928">
</a>
<a class="indexterm" name="idm46045218513424">
</a>
<a class="indexterm" name="idm46045218512336">
</a>
<p>
<em class="replaceable">
<code>
interval_expr
</code>
</em>
in expressions
represents a temporal interval. Intervals have this syntax:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa67918453"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">INTERVAL</span> <em class="replaceable">expr</em> <em class="replaceable">unit</em></code></pre>
</div>
<p>
<em class="replaceable">
<code>
expr
</code>
</em>
represents a quantity.
<em class="replaceable">
<code>
unit
</code>
</em>
represents the unit for
interpreting the quantity; it is a specifier such as
<code class="literal">
HOUR
</code>
,
<code class="literal">
DAY
</code>
, or
<code class="literal">
WEEK
</code>
. The
<code class="literal">
INTERVAL
</code>
keyword
and the
<em class="replaceable">
<code>
unit
</code>
</em>
specifier are not
case-sensitive.
</p>
<p>
The following table shows the expected form of the
<em class="replaceable">
<code>
expr
</code>
</em>
argument for each
<em class="replaceable">
<code>
unit
</code>
</em>
value.
</p>
<div class="table">
<a name="temporal-interval-arguments">
</a>
<p class="title">
<b>
Table 11.2 Temporal Interval Expression and Unit Arguments
</b>
</p>
<div class="table-contents">
<table summary="unit values and the expected expr argument for each unit value.">
<colgroup>
<col style="width: 50%"/>
<col style="width: 50%"/>
</colgroup>
<thead>
<tr>
<th>
<em class="replaceable">
<code>
unit
</code>
</em>
Value
</th>
<th>
Expected
<em class="replaceable">
<code>
expr
</code>
</em>
Format
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
MICROSECOND
</code>
</td>
<td>
<code class="literal">
MICROSECONDS
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
SECOND
</code>
</td>
<td>
<code class="literal">
SECONDS
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
MINUTE
</code>
</td>
<td>
<code class="literal">
MINUTES
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
HOUR
</code>
</td>
<td>
<code class="literal">
HOURS
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
DAY
</code>
</td>
<td>
<code class="literal">
DAYS
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
WEEK
</code>
</td>
<td>
<code class="literal">
WEEKS
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
MONTH
</code>
</td>
<td>
<code class="literal">
MONTHS
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
QUARTER
</code>
</td>
<td>
<code class="literal">
QUARTERS
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
YEAR
</code>
</td>
<td>
<code class="literal">
YEARS
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
SECOND_MICROSECOND
</code>
</td>
<td>
<code class="literal">
'SECONDS.MICROSECONDS'
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
MINUTE_MICROSECOND
</code>
</td>
<td>
<code class="literal">
'MINUTES:SECONDS.MICROSECONDS'
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
MINUTE_SECOND
</code>
</td>
<td>
<code class="literal">
'MINUTES:SECONDS'
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
HOUR_MICROSECOND
</code>
</td>
<td>
<code class="literal">
'HOURS:MINUTES:SECONDS.MICROSECONDS'
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
HOUR_SECOND
</code>
</td>
<td>
<code class="literal">
'HOURS:MINUTES:SECONDS'
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
HOUR_MINUTE
</code>
</td>
<td>
<code class="literal">
'HOURS:MINUTES'
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
DAY_MICROSECOND
</code>
</td>
<td>
<code class="literal">
'DAYS HOURS:MINUTES:SECONDS.MICROSECONDS'
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
DAY_SECOND
</code>
</td>
<td>
<code class="literal">
'DAYS HOURS:MINUTES:SECONDS'
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
DAY_MINUTE
</code>
</td>
<td>
<code class="literal">
'DAYS HOURS:MINUTES'
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
DAY_HOUR
</code>
</td>
<td>
<code class="literal">
'DAYS HOURS'
</code>
</td>
</tr>
<tr>
<td>
<code class="literal">
YEAR_MONTH
</code>
</td>
<td>
<code class="literal">
'YEARS-MONTHS'
</code>
</td>
</tr>
</tbody>
</table>
</div>
<div class="table-contents">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 401px; width: 681px;">
<thead>
<tr>
<th style="width: 340.141px;">
<em class="replaceable">
<code>
unit
</code>
</em>
Value
</th>
<th style="width: 340.141px;">
Expected
<em class="replaceable">
<code>
expr
</code>
</em>
Format
</th>
</tr>
</thead>
</table>
</div>
</div>
<br class="table-break"/>
<p>
MySQL permits any punctuation delimiter in the
<em class="replaceable">
<code>
expr
</code>
</em>
format. Those shown in the table
are the suggested delimiters.
</p>
<p>
Temporal intervals are used for certain functions, such as
<a class="link" href="date-and-time-functions.html#function_date-add">
<code class="literal">
DATE_ADD()
</code>
</a>
and
<a class="link" href="date-and-time-functions.html#function_date-sub">
<code class="literal">
DATE_SUB()
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa98324662"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2018-05-01'</span><span class="token punctuation">,</span><span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2018-05-02'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_SUB</span><span class="token punctuation">(</span><span class="token string">'2018-05-01'</span><span class="token punctuation">,</span><span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token datatype">YEAR</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2017-05-01'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2020-12-31 23:59:59'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">SECOND</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2021-01-01 00:00:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2018-12-31 23:59:59'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2019-01-01 23:59:59'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2100-12-31 23:59:59'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token string">'1:1'</span> <span class="token keyword">MINUTE_SECOND</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2101-01-01 00:01:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_SUB</span><span class="token punctuation">(</span><span class="token string">'2025-01-01 00:00:00'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token string">'1 1:1:1'</span> <span class="token keyword">DAY_SECOND</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2024-12-30 22:58:59'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'1900-01-01 00:00:00'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token string">'-1 10'</span> <span class="token keyword">DAY_HOUR</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'1899-12-30 14:00:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_SUB</span><span class="token punctuation">(</span><span class="token string">'1998-01-02'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">31</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'1997-12-02'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'1992-12-31 23:59:59.000002'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token string">'1.999999'</span> <span class="token keyword">SECOND_MICROSECOND</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'1993-01-01 00:00:01.000001'</span></code></pre>
</div>
<p>
Temporal arithmetic also can be performed in expressions using
<code class="literal">
INTERVAL
</code>
together with the
<a class="link" href="arithmetic-functions.html#operator_plus">
<code class="literal">
+
</code>
</a>
or
<a class="link" href="arithmetic-functions.html#operator_minus">
<code class="literal">
-
</code>
</a>
operator:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa53990518"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token datatype">date</span> <span class="token operator">+</span> <span class="token keyword">INTERVAL</span> <em class="replaceable">expr</em> <em class="replaceable">unit</em>
<span class="token datatype">date</span> <span class="token operator">-</span> <span class="token keyword">INTERVAL</span> <em class="replaceable">expr</em> <em class="replaceable">unit</em></code></pre>
</div>
<p>
<code class="literal">
INTERVAL
<em class="replaceable">
<code>
expr
</code>
</em>
<em class="replaceable">
<code>
unit
</code>
</em>
</code>
is permitted on either
side of the
<a class="link" href="arithmetic-functions.html#operator_plus">
<code class="literal">
+
</code>
</a>
operator if the expression on the other side is a date or
datetime value. For the
<a class="link" href="arithmetic-functions.html#operator_minus">
<code class="literal">
-
</code>
</a>
operator,
<code class="literal">
INTERVAL
<em class="replaceable">
<code>
expr
</code>
</em>
<em class="replaceable">
<code>
unit
</code>
</em>
</code>
is permitted only on
the right side, because it makes no sense to subtract a date or
datetime value from an interval.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa85998782"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token string">'2018-12-31 23:59:59'</span> <span class="token operator">+</span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">SECOND</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2019-01-01 00:00:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">DAY</span> <span class="token operator">+</span> <span class="token string">'2018-12-31'</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2019-01-01'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token string">'2025-01-01'</span> <span class="token operator">-</span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">SECOND</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2024-12-31 23:59:59'</span></code></pre>
</div>
<p>
The
<a class="link" href="date-and-time-functions.html#function_extract">
<code class="literal">
EXTRACT()
</code>
</a>
function uses the
same kinds of
<em class="replaceable">
<code>
unit
</code>
</em>
specifiers as
<a class="link" href="date-and-time-functions.html#function_date-add">
<code class="literal">
DATE_ADD()
</code>
</a>
or
<a class="link" href="date-and-time-functions.html#function_date-sub">
<code class="literal">
DATE_SUB()
</code>
</a>
, but extracts parts
from the date rather than performing date arithmetic:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa86685915"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">EXTRACT</span><span class="token punctuation">(</span><span class="token datatype">YEAR</span> <span class="token keyword">FROM</span> <span class="token string">'2019-07-02'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">2019</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">EXTRACT</span><span class="token punctuation">(</span><span class="token keyword">YEAR_MONTH</span> <span class="token keyword">FROM</span> <span class="token string">'2019-07-02 01:02:03'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">201907</span></code></pre>
</div>
<p>
Temporal intervals can be used in
<a class="link" href="create-event.html" title="15.1.13 CREATE EVENT Statement">
<code class="literal">
CREATE
EVENT
</code>
</a>
statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa66032978"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">EVENT</span> myevent
<span class="token keyword">ON</span> <span class="token keyword">SCHEDULE</span> <span class="token keyword">AT</span> <span class="token keyword">CURRENT_TIMESTAMP</span> <span class="token operator">+</span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">HOUR</span>
<span class="token keyword">DO</span>
<span class="token keyword">UPDATE</span> myschema<span class="token punctuation">.</span>mytable <span class="token keyword">SET</span> mycol <span class="token operator">=</span> mycol <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If you specify an interval value that is too short (does not
include all the interval parts that would be expected from the
<em class="replaceable">
<code>
unit
</code>
</em>
keyword), MySQL assumes that you
have left out the leftmost parts of the interval value. For
example, if you specify a
<em class="replaceable">
<code>
unit
</code>
</em>
of
<code class="literal">
DAY_SECOND
</code>
, the value of
<em class="replaceable">
<code>
expr
</code>
</em>
is expected to have days, hours,
minutes, and seconds parts. If you specify a value like
<code class="literal">
'1:10'
</code>
, MySQL assumes that the days and hours
parts are missing and the value represents minutes and seconds.
In other words,
<code class="literal">
'1:10' DAY_SECOND
</code>
is
interpreted in such a way that it is equivalent to
<code class="literal">
'1:10' MINUTE_SECOND
</code>
. This is analogous to
the way that MySQL interprets
<a class="link" href="time.html" title="13.2.3 The TIME Type">
<code class="literal">
TIME
</code>
</a>
values as representing
elapsed time rather than as a time of day.
</p>
<p>
<em class="replaceable">
<code>
expr
</code>
</em>
is treated as a string, so be
careful if you specify a nonstring value with
<code class="literal">
INTERVAL
</code>
. For example, with an interval
specifier of
<code class="literal">
HOUR_MINUTE
</code>
, '6/4' is treated as
6 hours, four minutes, whereas
<code class="literal">
6/4
</code>
evaluates
to
<code class="literal">
1.5000
</code>
and is treated as 1 hour, 5000
minutes:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60546875"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token string">'6/4'</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token operator">/</span><span class="token number">4</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">1.5000</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2019-01-01'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token string">'6/4'</span> <span class="token keyword">HOUR_MINUTE</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2019-01-01 06:04:00'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2019-01-01'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">6</span><span class="token operator">/</span><span class="token number">4</span> <span class="token keyword">HOUR_MINUTE</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2019-01-04 12:20:00'</span></code></pre>
</div>
<p>
To ensure interpretation of the interval value as you expect, a
<a class="link" href="cast-functions.html#function_cast">
<code class="literal">
CAST()
</code>
</a>
operation may be used. To
treat
<code class="literal">
6/4
</code>
as 1 hour, 5 minutes, cast it to a
<a class="link" href="fixed-point-types.html" title="13.1.3 Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC">
<code class="literal">
DECIMAL
</code>
</a>
value with a single
fractional digit:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa29285044"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">CAST</span><span class="token punctuation">(</span><span class="token number">6</span><span class="token operator">/</span><span class="token number">4</span> <span class="token keyword">AS</span> <span class="token datatype">DECIMAL</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token number">1.5</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'1970-01-01 12:00:00'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">INTERVAL</span> <span class="token function">CAST</span><span class="token punctuation">(</span><span class="token number">6</span><span class="token operator">/</span><span class="token number">4</span> <span class="token keyword">AS</span> <span class="token datatype">DECIMAL</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">HOUR_MINUTE</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'1970-01-01 13:05:00'</span></code></pre>
</div>
<p>
If you add to or subtract from a date value something that
contains a time part, the result is automatically converted to a
datetime value:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47125288"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2023-01-01'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2023-01-02'</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2023-01-01'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">HOUR</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2023-01-01 01:00:00'</span></code></pre>
</div>
<p>
If you add
<code class="literal">
MONTH
</code>
,
<code class="literal">
YEAR_MONTH
</code>
, or
<code class="literal">
YEAR
</code>
and
the resulting date has a day that is larger than the maximum day
for the new month, the day is adjusted to the maximum days in
the new month:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51841626"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2019-01-30'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">MONTH</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token string">'2019-02-28'</span></code></pre>
</div>
<p>
Date arithmetic operations require complete dates and do not
work with incomplete dates such as
<code class="literal">
'2016-07-00'
</code>
or badly malformed dates:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa46201224"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">DATE_ADD</span><span class="token punctuation">(</span><span class="token string">'2016-07-00'</span><span class="token punctuation">,</span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">DAY</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token boolean">NULL</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token string">'2005-03-32'</span> <span class="token operator">+</span> <span class="token keyword">INTERVAL</span> <span class="token number">1</span> <span class="token keyword">MONTH</span><span class="token punctuation">;</span>
<span class="token prompt"> -></span> <span class="token boolean">NULL</span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/charset-collation-compatibility.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="charset-collation-compatibility">
</a>
12.8.3 Character Set and Collation Compatibility
</h3>
</div>
</div>
</div>
<p>
Each character set has one or more collations, but each
collation is associated with one and only one character set.
Therefore, the following statement causes an error message
because the
<code class="literal">
latin2_bin
</code>
collation is not legal
with the
<code class="literal">
latin1
</code>
character set:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa24755424"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> _latin1 <span class="token string">'x'</span> <span class="token keyword">COLLATE</span> latin2_bin<span class="token punctuation">;</span>
<span class="token output">ERROR 1253 (42000)<span class="token punctuation">:</span> COLLATION 'latin2_bin' is not valid
for CHARACTER SET 'latin1'</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-host-summary-by-statement-latency.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-host-summary-by-statement-latency">
</a>
30.4.3.5 The host_summary_by_statement_latency and
x$host_summary_by_statement_latency Views
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045063264112">
</a>
<a class="indexterm" name="idm46045063262656">
</a>
<a class="indexterm" name="idm46045063261152">
</a>
<a class="indexterm" name="idm46045063259632">
</a>
<p>
These views summarize overall statement statistics, grouped by
host. By default, rows are sorted by descending total latency.
</p>
<p>
The
<a class="link" href="sys-host-summary-by-statement-latency.html" title="30.4.3.5 The host_summary_by_statement_latency and x$host_summary_by_statement_latency Views">
<code class="literal">
host_summary_by_statement_latency
</code>
</a>
and
<a class="link" href="sys-host-summary-by-statement-latency.html" title="30.4.3.5 The host_summary_by_statement_latency and x$host_summary_by_statement_latency Views">
<code class="literal">
x$host_summary_by_statement_latency
</code>
</a>
views have these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
host
</code>
</p>
<p>
The host from which the client connected. Rows for which
the
<code class="literal">
HOST
</code>
column in the underlying
Performance Schema table is
<code class="literal">
NULL
</code>
are
assumed to be for background threads and are reported with
a host name of
<code class="literal">
background
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
total
</code>
</p>
<p>
The total number of statements for the host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
total_latency
</code>
</p>
<p>
The total wait time of timed statements for the host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
max_latency
</code>
</p>
<p>
The maximum single wait time of timed statements for the
host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
lock_latency
</code>
</p>
<p>
The total time waiting for locks by timed statements for
the host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
cpu_latency
</code>
</p>
<p>
The time spent on CPU for the current thread.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_sent
</code>
</p>
<p>
The total number of rows returned by statements for the
host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_examined
</code>
</p>
<p>
The total number of rows read from storage engines by
statements for the host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_affected
</code>
</p>
<p>
The total number of rows affected by statements for the
host.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
full_scans
</code>
</p>
<p>
The total number of full table scans by statements for the
host.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/version-tokens.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="version-tokens">
</a>
7.6.6 Version Tokens
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="version-tokens-elements.html">
7.6.6.1 Version Tokens Elements
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="version-tokens-installation.html">
7.6.6.2 Installing or Uninstalling Version Tokens
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="version-tokens-usage.html">
7.6.6.3 Using Version Tokens
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="version-tokens-reference.html">
7.6.6.4 Version Tokens Reference
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045256131136">
</a>
<p>
MySQL includes Version Tokens, a feature that enables creation of
and synchronization around server tokens that applications can use
to prevent accessing incorrect or out-of-date data.
</p>
<p>
The Version Tokens interface has these characteristics:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Version tokens are pairs consisting of a name that serves as a
key or identifier, plus a value.
</p>
</li>
<li class="listitem">
<p>
Version tokens can be locked. An application can use token
locks to indicate to other cooperating applications that
tokens are in use and should not be modified.
</p>
</li>
<li class="listitem">
<p>
Version token lists are established per server (for example,
to specify the server assignment or operational state). In
addition, an application that communicates with a server can
register its own list of tokens that indicate the state it
requires the server to be in. An SQL statement sent by the
application to a server not in the required state produces an
error. This is a signal to the application that it should seek
a different server in the required state to receive the SQL
statement.
</p>
</li>
</ul>
</div>
<p>
The following sections describe the elements of Version Tokens,
discuss how to install and use it, and provide reference
information for its elements.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-locking-transaction-model.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="innodb-locking-transaction-model">
</a>
17.7 InnoDB Locking and Transaction Model
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="innodb-locking.html">
17.7.1 InnoDB Locking
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-transaction-model.html">
17.7.2 InnoDB Transaction Model
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-locks-set.html">
17.7.3 Locks Set by Different SQL Statements in InnoDB
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-next-key-locking.html">
17.7.4 Phantom Rows
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-deadlocks.html">
17.7.5 Deadlocks in InnoDB
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="innodb-transaction-scheduling.html">
17.7.6 Transaction Scheduling
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045164619200">
</a>
<a class="indexterm" name="idm46045164617808">
</a>
<a class="indexterm" name="idm46045164616416">
</a>
<a class="indexterm" name="idm46045164615408">
</a>
<p>
To implement a large-scale, busy, or highly reliable database
application, to port substantial code from a different database
system, or to tune MySQL performance, it is important to understand
<code class="literal">
InnoDB
</code>
locking and the
<code class="literal">
InnoDB
</code>
transaction model.
</p>
<p>
This section discusses several topics related to
<code class="literal">
InnoDB
</code>
locking and the
<code class="literal">
InnoDB
</code>
transaction model with which you should be familiar.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="innodb-locking.html" title="17.7.1 InnoDB Locking">
Section 17.7.1, “InnoDB Locking”
</a>
describes lock types used by
<code class="literal">
InnoDB
</code>
.
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="innodb-transaction-model.html" title="17.7.2 InnoDB Transaction Model">
Section 17.7.2, “InnoDB Transaction Model”
</a>
describes transaction
isolation levels and the locking strategies used by each. It
also discusses the use of
<a class="link" href="server-system-variables.html#sysvar_autocommit">
<code class="literal">
autocommit
</code>
</a>
, consistent
non-locking reads, and locking reads.
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="innodb-locks-set.html" title="17.7.3 Locks Set by Different SQL Statements in InnoDB">
Section 17.7.3, “Locks Set by Different SQL Statements in InnoDB”
</a>
discusses specific types of
locks set in
<code class="literal">
InnoDB
</code>
for various statements.
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="innodb-next-key-locking.html" title="17.7.4 Phantom Rows">
Section 17.7.4, “Phantom Rows”
</a>
describes how
<code class="literal">
InnoDB
</code>
uses next-key locking to avoid phantom
rows.
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="innodb-deadlocks.html" title="17.7.5 Deadlocks in InnoDB">
Section 17.7.5, “Deadlocks in InnoDB”
</a>
provides a deadlock example,
discusses deadlock detection, and provides tips for minimizing
and handling deadlocks in
<code class="literal">
InnoDB
</code>
.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-options-binary-log.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-options-binary-log">
</a>
19.1.6.4 Binary Logging Options and Variables
</h4>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="replication-options-binary-log.html#replication-optvars-binlog" title="Startup Options Used with Binary Logging">
Startup Options Used with Binary Logging
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="replication-options-binary-log.html#replication-sysvars-binlog" title="System Variables Used with Binary Logging">
System Variables Used with Binary Logging
</a>
</p>
</li>
</ul>
</div>
<p>
You can use the
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
options and system
variables that are described in this section to affect the
operation of the binary log as well as to control which statements
are written to the binary log. For additional information about
the binary log, see
<a class="xref" href="binary-log.html" title="7.4.4 The Binary Log">
Section 7.4.4, “The Binary Log”
</a>
. For additional
information about using MySQL server options and system variables,
see
<a class="xref" href="server-options.html" title="7.1.7 Server Command Options">
Section 7.1.7, “Server Command Options”
</a>
, and
<a class="xref" href="server-system-variables.html" title="7.1.8 Server System Variables">
Section 7.1.8, “Server System Variables”
</a>
.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="replication-optvars-binlog">
</a>
Startup Options Used with Binary Logging
</h5>
</div>
</div>
</div>
<p>
The following list describes startup options for enabling and
configuring the binary log. System variables used with binary
logging are discussed later in this section.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="option_mysqld_binlog-row-event-max-size">
</a>
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-row-event-max-size">
<code class="option">
--binlog-row-event-max-size=
<em class="replaceable">
<code>
N
</code>
</em>
</code>
</a>
</p>
<a class="indexterm" name="idm46045140972496">
</a>
<a class="indexterm" name="idm46045140970992">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog-row-event-max-size">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-row-event-max-size=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_row_event_max_size">
binlog_row_event_max_size
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
8192
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
256
</code>
</td>
</tr>
<tr>
<th>
Maximum Value (64-bit platforms)
</th>
<td>
<code class="literal">
18446744073709551615
</code>
</td>
</tr>
<tr>
<th>
Maximum Value (32-bit platforms)
</th>
<td>
<code class="literal">
4294967295
</code>
</td>
</tr>
<tr>
<th>
Unit
</th>
<td>
bytes
</td>
</tr>
</tbody>
</table>
</div>
<p>
When row-based binary logging is used, this setting is a
soft limit on the maximum size of a row-based binary log
event, in bytes. Where possible, rows stored in the binary
log are grouped into events with a size not exceeding the
value of this setting. If an event cannot be split, the
maximum size can be exceeded. The value must be (or else
gets rounded down to) a multiple of 256. The default is 8192
bytes.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqld_log-bin">
</a>
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--log-bin[=
<em class="replaceable">
<code>
base_name
</code>
</em>
]
</code>
</a>
</p>
<a class="indexterm" name="idm46045140936496">
</a>
<a class="indexterm" name="idm46045140935008">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for log-bin">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--log-bin=file_name
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
File name
</td>
</tr>
</tbody>
</table>
</div>
<p>
Specifies the base name to use for binary log files. With
binary logging enabled, the server logs all statements that
change data to the binary log, which is used for backup and
replication. The binary log is a sequence of files with a
base name and numeric extension. The
<code class="option">
--log-bin
</code>
option value is the base name for
the log sequence. The server creates binary log files in
sequence by adding a numeric suffix to the base name.
</p>
<p>
If you do not supply the
<code class="option">
--log-bin
</code>
option,
MySQL uses
<code class="filename">
binlog
</code>
as the default base
name for the binary log files. For compatibility with
earlier releases, if you supply the
<code class="option">
--log-bin
</code>
option with no string or with an
empty string, the base name defaults to
<code class="filename">
<em class="replaceable">
<code>
host_name
</code>
</em>
-bin
</code>
,
using the name of the host machine.
</p>
<p>
The default location for binary log files is the data
directory. You can use the
<code class="option">
--log-bin
</code>
option
to specify an alternative location, by adding a leading
absolute path name to the base name to specify a different
directory. When the server reads an entry from the binary
log index file, which tracks the binary log files that have
been used, it checks whether the entry contains a relative
path. If it does, the relative part of the path is replaced
with the absolute path set using the
<code class="option">
--log-bin
</code>
option. An absolute path recorded
in the binary log index file remains unchanged; in such a
case, the index file must be edited manually to enable a new
path or paths to be used. The binary log file base name and
any specified path are available as the
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin_basename">
<code class="literal">
log_bin_basename
</code>
</a>
system
variable.
</p>
<p>
In MySQL 8.4, binary logging is enabled by
default, whether or not you specify the
<code class="option">
--log-bin
</code>
option. The exception is if you
use
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
to initialize the data
directory manually by invoking it with the
<code class="option">
--initialize
</code>
or
<code class="option">
--initialize-insecure
</code>
option, when binary
logging is disabled by default. It is possible to enable
binary logging in this case by specifying the
<code class="option">
--log-bin
</code>
option. When binary logging is
enabled, the
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin">
<code class="literal">
log_bin
</code>
</a>
system
variable, which shows the status of binary logging on the
server, is set to ON.
</p>
<p>
To disable binary logging, you can specify the
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--skip-log-bin
</code>
</a>
or
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--disable-log-bin
</code>
</a>
option at startup. If either of these options is specified
and
<code class="option">
--log-bin
</code>
is also specified, the option
specified later takes precedence. When binary logging is
disabled, the
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin">
<code class="literal">
log_bin
</code>
</a>
system variable is set to OFF.
</p>
<p>
When GTIDs are in use on the server, if you disable binary
logging when restarting the server after an abnormal
shutdown, some GTIDs are likely to be lost, causing
replication to fail. In a normal shutdown, the set of GTIDs
from the current binary log file is saved in the
<code class="literal">
mysql.gtid_executed
</code>
table. Following an
abnormal shutdown where this did not happen, during recovery
the GTIDs are added to the table from the binary log file,
provided that binary logging is still enabled. If binary
logging is disabled for the server restart, the server
cannot access the binary log file to recover the GTIDs, so
replication cannot be started. Binary logging can be
disabled safely after a normal shutdown.
</p>
<p>
The
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="option">
--log-replica-updates
</code>
</a>
and
<a class="link" href="replication-options-replica.html#sysvar_replica_preserve_commit_order">
<code class="option">
--replica-preserve-commit-order
</code>
</a>
options require binary logging. If you disable binary
logging, either omit these options, or specify
<code class="option">
--log-replica-updates=OFF
</code>
and
<code class="option">
--skip-replica-preserve-commit-order
</code>
. MySQL
disables these options by default when
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--skip-log-bin
</code>
</a>
or
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--disable-log-bin
</code>
</a>
is specified. If you specify
<code class="option">
--log-replica-updates
</code>
or
<code class="option">
--replica-preserve-commit-order
</code>
together
with
<code class="option">
--skip-log-bin
</code>
or
<code class="option">
--disable-log-bin
</code>
, a warning or error
message is issued.
</p>
<p>
The server can be started with the default server ID when
binary logging is enabled, but an informational message is
issued if you do not specify a server ID explicitly by
setting the
<a class="link" href="replication-options.html#sysvar_server_id">
<code class="literal">
server_id
</code>
</a>
system variable. For servers that are used in a replication
topology, you must specify a unique nonzero server ID for
each server.
</p>
<p>
For information on the format and management of the binary
log, see
<a class="xref" href="binary-log.html" title="7.4.4 The Binary Log">
Section 7.4.4, “The Binary Log”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqld_log-bin-index">
</a>
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin-index">
<code class="option">
--log-bin-index[=
<em class="replaceable">
<code>
file_name
</code>
</em>
]
</code>
</a>
</p>
<a class="indexterm" name="idm46045140893200">
</a>
<a class="indexterm" name="idm46045140891712">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for log-bin-index">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--log-bin-index=file_name
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin_index">
log_bin_index
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
File name
</td>
</tr>
</tbody>
</table>
</div>
<p>
The name for the binary log index file, which contains the
names of the binary log files. By default, it has the same
location and base name as the value specified for the binary
log files using the
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--log-bin
</code>
</a>
option, plus the extension
<code class="filename">
.index
</code>
. If
you do not specify
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--log-bin
</code>
</a>
,
the default binary log index file name is
<code class="filename">
binlog.index
</code>
. If you specify
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--log-bin
</code>
</a>
option with no
string or an empty string, the default binary log index file
name is
<code class="filename">
<em class="replaceable">
<code>
host_name
</code>
</em>
-bin.index
</code>
,
using the name of the host machine.
</p>
<p>
For information on the format and management of the binary
log, see
<a class="xref" href="binary-log.html" title="7.4.4 The Binary Log">
Section 7.4.4, “The Binary Log”
</a>
.
</p>
</li>
</ul>
</div>
<p>
<b>
Statement selection options.
</b>
The options in the following list affect which statements are
written to the binary log, and thus sent by a replication
source server to its replicas. There are also options for
replicas that control which statements received from the
source should be executed or ignored. For details, see
<a class="xref" href="replication-options-replica.html" title="19.1.6.3 Replica Server Options and Variables">
Section 19.1.6.3, “Replica Server Options and Variables”
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="option_mysqld_binlog-do-db">
</a>
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db">
<code class="option">
--binlog-do-db=
<em class="replaceable">
<code>
db_name
</code>
</em>
</code>
</a>
</p>
<a class="indexterm" name="idm46045140859856">
</a>
<a class="indexterm" name="idm46045140858368">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog-do-db">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-do-db=name
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<p>
This option affects binary logging in a manner similar to
the way that
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-db">
<code class="option">
--replicate-do-db
</code>
</a>
affects
replication.
</p>
<p>
The effects of this option depend on whether the
statement-based or row-based logging format is in use, in
the same way that the effects of
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-db">
<code class="option">
--replicate-do-db
</code>
</a>
depend on
whether statement-based or row-based replication is in use.
You should keep in mind that the format used to log a given
statement may not necessarily be the same as that indicated
by the value of
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
. For example,
DDL statements such as
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE
TABLE
</code>
</a>
and
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
are always logged as statements, without
regard to the logging format in effect, so the following
statement-based rules for
<code class="option">
--binlog-do-db
</code>
always apply in determining whether or not the statement is
logged.
</p>
<p>
<b>
Statement-based logging.
</b>
Only those statements are written to the binary log where
the default database (that is, the one selected by
<a class="link" href="use.html" title="15.8.4 USE Statement">
<code class="literal">
USE
</code>
</a>
) is
<em class="replaceable">
<code>
db_name
</code>
</em>
. To specify more than
one database, use this option multiple times, once for
each database; however, doing so does
<span class="emphasis">
<em>
not
</em>
</span>
cause cross-database statements
such as
<code class="literal">
UPDATE
<em class="replaceable">
<code>
some_db.some_table
</code>
</em>
SET
foo='bar'
</code>
to be logged while a different
database (or no database) is selected.
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
To specify multiple databases you
<span class="emphasis">
<em>
must
</em>
</span>
use multiple instances of this
option. Because database names can contain commas, the
list is treated as the name of a single database if you
supply a comma-separated list.
</p>
</div>
<p>
An example of what does not work as you might expect when
using statement-based logging: If the server is started with
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db">
<code class="option">
--binlog-do-db=sales
</code>
</a>
and you
issue the following statements, the
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement is
<span class="emphasis">
<em>
not
</em>
</span>
logged:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa96905284"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">USE</span> prices<span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> sales<span class="token punctuation">.</span>january <span class="token keyword">SET</span> amount<span class="token operator">=</span>amount<span class="token operator">+</span><span class="token number">1000</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The main reason for this
<span class="quote">
“
<span class="quote">
just check the default
database
</span>
”
</span>
behavior is that it is difficult from the
statement alone to know whether it should be replicated (for
example, if you are using multiple-table
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
statements or
multiple-table
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statements that act across multiple databases). It is also
faster to check only the default database rather than all
databases if there is no need.
</p>
<p>
Another case which may not be self-evident occurs when a
given database is replicated even though it was not
specified when setting the option. If the server is started
with
<code class="option">
--binlog-do-db=sales
</code>
, the following
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement is logged
even though
<code class="literal">
prices
</code>
was not included when
setting
<code class="option">
--binlog-do-db
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa19129214"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">USE</span> sales<span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> prices<span class="token punctuation">.</span>discounts <span class="token keyword">SET</span> percentage <span class="token operator">=</span> percentage <span class="token operator">+</span> <span class="token number">10</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Because
<code class="literal">
sales
</code>
is the default database
when the
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement is
issued, the
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
is logged.
</p>
<p>
<b>
Row-based logging.
</b>
Logging is restricted to database
<em class="replaceable">
<code>
db_name
</code>
</em>
. Only changes to tables
belonging to
<em class="replaceable">
<code>
db_name
</code>
</em>
are
logged; the default database has no effect on this.
Suppose that the server is started with
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db">
<code class="option">
--binlog-do-db=sales
</code>
</a>
and
row-based logging is in effect, and then the following
statements are executed:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa27066417"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">USE</span> prices<span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> sales<span class="token punctuation">.</span>february <span class="token keyword">SET</span> amount<span class="token operator">=</span>amount<span class="token operator">+</span><span class="token number">100</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The changes to the
<code class="literal">
february
</code>
table in the
<code class="literal">
sales
</code>
database are logged in accordance
with the
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement;
this occurs whether or not the
<a class="link" href="use.html" title="15.8.4 USE Statement">
<code class="literal">
USE
</code>
</a>
statement was issued.
However, when using the row-based logging format and
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db">
<code class="option">
--binlog-do-db=sales
</code>
</a>
, changes
made by the following
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
are not logged:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa35599520"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">USE</span> prices<span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> prices<span class="token punctuation">.</span>march <span class="token keyword">SET</span> amount<span class="token operator">=</span>amount<span class="token number">-25</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Even if the
<code class="literal">
USE prices
</code>
statement were
changed to
<code class="literal">
USE sales
</code>
, the
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement's
effects would still not be written to the binary log.
</p>
<p>
Another important difference in
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db">
<code class="option">
--binlog-do-db
</code>
</a>
handling for
statement-based logging as opposed to the row-based logging
occurs with regard to statements that refer to multiple
databases. Suppose that the server is started with
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db">
<code class="option">
--binlog-do-db=db1
</code>
</a>
, and the
following statements are executed:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa65042111"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">USE</span> db1<span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> db1<span class="token punctuation">.</span>table1<span class="token punctuation">,</span> db2<span class="token punctuation">.</span>table2 <span class="token keyword">SET</span> db1<span class="token punctuation">.</span>table1<span class="token punctuation">.</span>col1 <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">,</span> db2<span class="token punctuation">.</span>table2<span class="token punctuation">.</span>col2 <span class="token operator">=</span> <span class="token number">20</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If you are using statement-based logging, the updates to
both tables are written to the binary log. However, when
using the row-based format, only the changes to
<code class="literal">
table1
</code>
are logged;
<code class="literal">
table2
</code>
is in a different database, so it
is not changed by the
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
.
Now suppose that, instead of the
<code class="literal">
USE db1
</code>
statement, a
<code class="literal">
USE db4
</code>
statement had been
used:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa95586039"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">USE</span> db4<span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> db1<span class="token punctuation">.</span>table1<span class="token punctuation">,</span> db2<span class="token punctuation">.</span>table2 <span class="token keyword">SET</span> db1<span class="token punctuation">.</span>table1<span class="token punctuation">.</span>col1 <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">,</span> db2<span class="token punctuation">.</span>table2<span class="token punctuation">.</span>col2 <span class="token operator">=</span> <span class="token number">20</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
In this case, the
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement is not written to the binary log when using
statement-based logging. However, when using row-based
logging, the change to
<code class="literal">
table1
</code>
is logged,
but not that to
<code class="literal">
table2
</code>
—in other
words, only changes to tables in the database named by
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db">
<code class="option">
--binlog-do-db
</code>
</a>
are logged,
and the choice of default database has no effect on this
behavior.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqld_binlog-ignore-db">
</a>
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db">
<code class="option">
--binlog-ignore-db=
<em class="replaceable">
<code>
db_name
</code>
</em>
</code>
</a>
</p>
<a class="indexterm" name="idm46045140787312">
</a>
<a class="indexterm" name="idm46045140785824">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog-ignore-db">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-ignore-db=name
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
</tbody>
</table>
</div>
<p>
This option affects binary logging in a manner similar to
the way that
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-ignore-db">
<code class="option">
--replicate-ignore-db
</code>
</a>
affects
replication.
</p>
<p>
The effects of this option depend on whether the
statement-based or row-based logging format is in use, in
the same way that the effects of
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-ignore-db">
<code class="option">
--replicate-ignore-db
</code>
</a>
depend
on whether statement-based or row-based replication is in
use. You should keep in mind that the format used to log a
given statement may not necessarily be the same as that
indicated by the value of
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
. For example,
DDL statements such as
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE
TABLE
</code>
</a>
and
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
are always logged as statements, without
regard to the logging format in effect, so the following
statement-based rules for
<code class="option">
--binlog-ignore-db
</code>
always apply in
determining whether or not the statement is logged.
</p>
<p>
<b>
Statement-based logging.
</b>
Tells the server to not log any statement where the
default database (that is, the one selected by
<a class="link" href="use.html" title="15.8.4 USE Statement">
<code class="literal">
USE
</code>
</a>
) is
<em class="replaceable">
<code>
db_name
</code>
</em>
.
</p>
<p>
When there is no default database, no
<code class="option">
--binlog-ignore-db
</code>
options are applied, and
such statements are always logged. (Bug #11829838, Bug
#60188)
</p>
<p>
<b>
Row-based format.
</b>
Tells the server not to log updates to any tables in the
database
<em class="replaceable">
<code>
db_name
</code>
</em>
. The current
database has no effect.
</p>
<p>
When using statement-based logging, the following example
does not work as you might expect. Suppose that the server
is started with
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db">
<code class="option">
--binlog-ignore-db=sales
</code>
</a>
and
you issue the following statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa67112553"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">USE</span> prices<span class="token punctuation">;</span>
<span class="token keyword">UPDATE</span> sales<span class="token punctuation">.</span>january <span class="token keyword">SET</span> amount<span class="token operator">=</span>amount<span class="token operator">+</span><span class="token number">1000</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement
<span class="emphasis">
<em>
is
</em>
</span>
logged in such a case because
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db">
<code class="option">
--binlog-ignore-db
</code>
</a>
applies
only to the default database (determined by the
<a class="link" href="use.html" title="15.8.4 USE Statement">
<code class="literal">
USE
</code>
</a>
statement). Because the
<code class="literal">
sales
</code>
database was specified explicitly
in the statement, the statement has not been filtered.
However, when using row-based logging, the
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement's
effects are
<span class="emphasis">
<em>
not
</em>
</span>
written to the binary
log, which means that no changes to the
<code class="literal">
sales.january
</code>
table are logged; in this
instance,
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db">
<code class="option">
--binlog-ignore-db=sales
</code>
</a>
causes
<span class="emphasis">
<em>
all
</em>
</span>
changes made to tables in
the source's copy of the
<code class="literal">
sales
</code>
database to be ignored for purposes of binary logging.
</p>
<p>
To specify more than one database to ignore, use this option
multiple times, once for each database. Because database
names can contain commas, the list is treated as the name of
a single database if you supply a comma-separated list.
</p>
<p>
You should not use this option if you are using
cross-database updates and you do not want these updates to
be logged.
</p>
</li>
</ul>
</div>
<p>
<a name="replication-optvars-binlog-checksums">
</a>
<b>
Checksum options.
</b>
MySQL supports reading and writing of binary log checksums.
These are enabled using the two options listed here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="option_mysqld_binlog-checksum">
</a>
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-checksum">
<code class="option">
--binlog-checksum={NONE|CRC32}
</code>
</a>
</p>
<a class="indexterm" name="idm46045140745104">
</a>
<a class="indexterm" name="idm46045140743616">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog-checksum">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-checksum=type
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
CRC32
</code>
</td>
</tr>
<tr>
<th>
Valid Values
</th>
<td>
<p class="valid-value">
<code class="literal">
NONE
</code>
</p>
<p class="valid-value">
<code class="literal">
CRC32
</code>
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Enabling this option causes the source to write checksums
for events written to the binary log. Set to
<code class="literal">
NONE
</code>
to disable, or the name of the
algorithm to be used for generating checksums; currently,
only CRC32 checksums are supported, and CRC32 is the
default. You cannot change the setting for this option
within a transaction.
</p>
</li>
</ul>
</div>
<p>
To control reading of checksums by the replica (from the relay
log), use the
<a class="link" href="replication-options-replica.html#sysvar_replica_sql_verify_checksum">
<code class="option">
--replica-sql-verify-checksum
</code>
</a>
option.
</p>
<p>
<b>
Testing and debugging options.
</b>
The following binary log options are used in replication
testing and debugging. They are not intended for use in normal
operations.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="option_mysqld_max-binlog-dump-events">
</a>
<a class="link" href="replication-options-binary-log.html#option_mysqld_max-binlog-dump-events">
<code class="option">
--max-binlog-dump-events=
<em class="replaceable">
<code>
N
</code>
</em>
</code>
</a>
</p>
<a class="indexterm" name="idm46045140720368">
</a>
<a class="indexterm" name="idm46045140718864">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for max-binlog-dump-events">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--max-binlog-dump-events=#
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
0
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This option is used internally by the MySQL test suite for
replication testing and debugging.
</p>
</li>
<li class="listitem">
<p>
<a name="option_mysqld_sporadic-binlog-dump-fail">
</a>
<a class="link" href="replication-options-binary-log.html#option_mysqld_sporadic-binlog-dump-fail">
<code class="option">
--sporadic-binlog-dump-fail
</code>
</a>
</p>
<a class="indexterm" name="idm46045140704624">
</a>
<a class="indexterm" name="idm46045140703120">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for sporadic-binlog-dump-fail">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--sporadic-binlog-dump-fail[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This option is used internally by the MySQL test suite for
replication testing and debugging.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="replication-sysvars-binlog">
</a>
System Variables Used with Binary Logging
</h5>
</div>
</div>
</div>
<p>
The following list describes system variables for controlling
binary logging. They can be set at server startup and some of
them can be changed at runtime using
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
.
Server options used to control binary logging are listed earlier
in this section.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a name="sysvar_binlog_cache_size">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_cache_size">
<code class="literal">
binlog_cache_size
</code>
</a>
</p>
<a class="indexterm" name="idm46045140685056">
</a>
<a class="indexterm" name="idm46045140684016">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_cache_size">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-cache-size=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_cache_size">
binlog_cache_size
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
32768
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
4096
</code>
</td>
</tr>
<tr>
<th>
Maximum Value (64-bit platforms)
</th>
<td>
<code class="literal">
18446744073709547520
</code>
</td>
</tr>
<tr>
<th>
Maximum Value (32-bit platforms)
</th>
<td>
<code class="literal">
4294963200
</code>
</td>
</tr>
<tr>
<th>
Unit
</th>
<td>
bytes
</td>
</tr>
<tr>
<th>
<a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
Block Size
</a>
</th>
<td>
<code class="literal">
4096
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The size of the memory buffer to hold changes to the binary
log during a transaction.
</p>
<p>
When binary logging is enabled on the server (with the
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin">
<code class="literal">
log_bin
</code>
</a>
system variable set
to ON), a binary log cache is allocated for each client if
the server supports any transactional storage engines. If
the data for the transaction exceeds the space in the memory
buffer, the excess data is stored in a temporary file. When
binary log encryption is active on the server, the memory
buffer is not encrypted, but any temporary file used to hold
the binary log cache is encrypted. After each transaction is
committed, the binary log cache is reset by clearing the
memory buffer and truncating the temporary file if used.
</p>
<p>
If you often use large transactions, you can increase this
cache size to get better performance by reducing or
eliminating the need to write to temporary files. The
<a class="link" href="server-status-variables.html#statvar_Binlog_cache_use">
<code class="literal">
Binlog_cache_use
</code>
</a>
and
<a class="link" href="server-status-variables.html#statvar_Binlog_cache_disk_use">
<code class="literal">
Binlog_cache_disk_use
</code>
</a>
status variables can be useful for tuning the size of this
variable. See
<a class="xref" href="binary-log.html" title="7.4.4 The Binary Log">
Section 7.4.4, “The Binary Log”
</a>
.
</p>
<p>
<code class="literal">
binlog_cache_size
</code>
sets the size for the
transaction cache only; the size of the statement cache is
governed by the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_stmt_cache_size">
<code class="literal">
binlog_stmt_cache_size
</code>
</a>
system variable.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_checksum">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_checksum">
<code class="literal">
binlog_checksum
</code>
</a>
</p>
<a class="indexterm" name="idm46045140637648">
</a>
<a class="indexterm" name="idm46045140636560">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_checksum">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-checksum=type
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_checksum">
binlog_checksum
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
String
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
CRC32
</code>
</td>
</tr>
<tr>
<th>
Valid Values
</th>
<td>
<p class="valid-value">
<code class="literal">
NONE
</code>
</p>
<p class="valid-value">
<code class="literal">
CRC32
</code>
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
When enabled, this variable causes the source to write a
checksum for each event in the binary log.
<code class="literal">
binlog_checksum
</code>
supports the values
<code class="literal">
NONE
</code>
(which disables checksums) and
<code class="literal">
CRC32
</code>
. The default is
<code class="literal">
CRC32
</code>
. When
<code class="literal">
binlog_checksum
</code>
is disabled (value
<code class="literal">
NONE
</code>
), the server verifies that it is
writing only complete events to the binary log by writing
and checking the event length (rather than a checksum) for
each event.
</p>
<p>
Setting this variable on the source to a value unrecognized
by the replica causes the replica to set its own
<code class="literal">
binlog_checksum
</code>
value to
<code class="literal">
NONE
</code>
, and to stop replication with an
error. If backward compatibility with older replicas is a
concern, you may want to set the value explicitly to
<code class="literal">
NONE
</code>
.
</p>
<p>
Group Replication in MySQL 8.4 supports
checksums, so group members may use the default setting.
</p>
<p>
Changing the value of
<code class="literal">
binlog_checksum
</code>
causes the binary log to be rotated, because checksums must
be written for an entire binary log file, and never for only
part of one. You cannot change the value of
<code class="literal">
binlog_checksum
</code>
within a transaction.
</p>
<p>
When binary log transaction compression is enabled using the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_compression">
<code class="literal">
binlog_transaction_compression
</code>
</a>
system variable, checksums are not written for individual
events in a compressed transaction payload. Instead a
checksum is written for the GTID event, and a checksum for
the compressed
<code class="literal">
Transaction_payload_event
</code>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_direct_non_transactional_updates">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_direct_non_transactional_updates">
<code class="literal">
binlog_direct_non_transactional_updates
</code>
</a>
</p>
<a class="indexterm" name="idm46045140595200">
</a>
<a class="indexterm" name="idm46045140594160">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_direct_non_transactional_updates">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-direct-non-transactional-updates[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_direct_non_transactional_updates">
binlog_direct_non_transactional_updates
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global, Session
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Due to concurrency issues, a replica can become inconsistent
when a transaction contains updates to both transactional
and nontransactional tables. MySQL tries to preserve
causality among these statements by writing nontransactional
statements to the transaction cache, which is flushed upon
commit. However, problems arise when modifications done to
nontransactional tables on behalf of a transaction become
immediately visible to other connections because these
changes may not be written immediately into the binary log.
</p>
<p>
The
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_direct_non_transactional_updates">
<code class="literal">
binlog_direct_non_transactional_updates
</code>
</a>
variable offers one possible workaround to this issue. By
default, this variable is disabled. Enabling
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_direct_non_transactional_updates">
<code class="literal">
binlog_direct_non_transactional_updates
</code>
</a>
causes updates to nontransactional tables to be written
directly to the binary log, rather than to the transaction
cache.
</p>
<p>
Setting the session value of this system variable is a
restricted operation. The session user must have privileges
sufficient to set restricted session variables. See
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
.
</p>
<p>
<span class="emphasis">
<em>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_direct_non_transactional_updates">
<code class="literal">
binlog_direct_non_transactional_updates
</code>
</a>
works only for statements that are replicated using the
statement-based binary logging format
</em>
</span>
; that is,
it works only when the value of
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
is
<code class="literal">
STATEMENT
</code>
, or when
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
is
<code class="literal">
MIXED
</code>
and a given statement is being
replicated using the statement-based format. This variable
has no effect when the binary log format is
<code class="literal">
ROW
</code>
, or when
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
is set to
<code class="literal">
MIXED
</code>
and a given statement is replicated
using the row-based format.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
Before enabling this variable, you must make certain that
there are no dependencies between transactional and
nontransactional tables; an example of such a dependency
would be the statement
<code class="literal">
INSERT INTO myisam_table
SELECT * FROM innodb_table
</code>
. Otherwise, such
statements are likely to cause the replica to diverge from
the source.
</p>
</div>
<p>
This variable has no effect when the binary log format is
<code class="literal">
ROW
</code>
or
<code class="literal">
MIXED
</code>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_encryption">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_encryption">
<code class="literal">
binlog_encryption
</code>
</a>
</p>
<a class="indexterm" name="idm46045140551520">
</a>
<a class="indexterm" name="idm46045140550480">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_encryption">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-encryption[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_encryption">
binlog_encryption
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Enables encryption for binary log files and relay log files
on this server.
<code class="literal">
OFF
</code>
is the default.
<code class="literal">
ON
</code>
sets encryption on for binary log
files and relay log files. Binary logging does not need to
be enabled on the server to enable encryption, so you can
encrypt the relay log files on a replica that has no binary
log. To use encryption, a keyring plugin must be installed
and configured to supply MySQL Server's keyring service. For
instructions to do this, see
<a class="xref" href="keyring.html" title="8.4.4 The MySQL Keyring">
Section 8.4.4, “The MySQL Keyring”
</a>
. Any
supported keyring plugin can be used to store binary log
encryption keys.
</p>
<p>
When you first start the server with binary log encryption
enabled, a new binary log encryption key is generated before
the binary log and relay logs are initialized. This key is
used to encrypt a file password for each binary log file (if
the server has binary logging enabled) and relay log file
(if the server has replication channels), and further keys
generated from the file passwords are used to encrypt the
data in the files. Relay log files are encrypted for all
channels, including Group Replication applier channels and
new channels that are created after encryption is activated.
The binary log index file and relay log index file are never
encrypted.
</p>
<p>
If you activate encryption while the server is running, a
new binary log encryption key is generated at that time. The
exception is if encryption was active previously on the
server and was then disabled, in which case the binary log
encryption key that was in use before is used again. The
binary log file and relay log files are rotated immediately,
and file passwords for the new files and all subsequent
binary log files and relay log files are encrypted using
this binary log encryption key. Existing binary log files
and relay log files still present on the server are not
automatically encrypted, but you can purge them if they are
no longer needed.
</p>
<p>
If you deactivate encryption by changing the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_encryption">
<code class="literal">
binlog_encryption
</code>
</a>
system
variable to
<code class="literal">
OFF
</code>
, the binary log file and
relay log files are rotated immediately and all subsequent
logging is unencrypted. Previously encrypted files are not
automatically decrypted, but the server is still able to
read them. The
<code class="literal">
BINLOG_ENCRYPTION_ADMIN
</code>
privilege (or the deprecated
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege) is required
to activate or deactivate encryption while the server is
running. Group Replication applier channels are not included
in the relay log rotation request, so unencrypted logging
for these channels does not start until their logs are
rotated in normal use.
</p>
<p>
For more information on binary log file and relay log file
encryption, see
<a class="xref" href="replication-binlog-encryption.html" title="19.3.2 Encrypting Binary Log Files and Relay Log Files">
Section 19.3.2, “Encrypting Binary Log Files and Relay Log Files”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_error_action">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_error_action">
<code class="literal">
binlog_error_action
</code>
</a>
</p>
<a class="indexterm" name="idm46045140514608">
</a>
<a class="indexterm" name="idm46045140513568">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_error_action">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-error-action[=value]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_error_action">
binlog_error_action
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Enumeration
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
ABORT_SERVER
</code>
</td>
</tr>
<tr>
<th>
Valid Values
</th>
<td>
<p class="valid-value">
<code class="literal">
IGNORE_ERROR
</code>
</p>
<p class="valid-value">
<code class="literal">
ABORT_SERVER
</code>
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Controls what happens when the server encounters an error
such as not being able to write to, flush or synchronize the
binary log, which can cause the source's binary log to
become inconsistent and replicas to lose synchronization.
</p>
<p>
This variable defaults to
<code class="literal">
ABORT_SERVER
</code>
,
which makes the server halt logging and shut down whenever
it encounters such an error with the binary log. On restart,
recovery proceeds as in the case of an unexpected server
halt (see
<a class="xref" href="replication-solutions-unexpected-replica-halt.html" title="19.4.2 Handling an Unexpected Halt of a Replica">
Section 19.4.2, “Handling an Unexpected Halt of a Replica”
</a>
).
</p>
<p>
When
<code class="literal">
binlog_error_action
</code>
is set to
<code class="literal">
IGNORE_ERROR
</code>
, if the server encounters
such an error it continues the ongoing transaction, logs the
error then halts logging, and continues performing updates.
To resume binary logging
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin">
<code class="literal">
log_bin
</code>
</a>
must be enabled
again, which requires a server restart. This setting
provides backward compatibility with older versions of
MySQL.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_expire_logs_seconds">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_expire_logs_seconds">
<code class="literal">
binlog_expire_logs_seconds
</code>
</a>
</p>
<a class="indexterm" name="idm46045140479408">
</a>
<a class="indexterm" name="idm46045140478320">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_expire_logs_seconds">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-expire-logs-seconds=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_expire_logs_seconds">
binlog_expire_logs_seconds
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
2592000
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
0
</code>
</td>
</tr>
<tr>
<th>
Maximum Value
</th>
<td>
<code class="literal">
4294967295
</code>
</td>
</tr>
<tr>
<th>
Unit
</th>
<td>
seconds
</td>
</tr>
</tbody>
</table>
</div>
<p>
Sets the binary log expiration period in seconds. After
their expiration period ends, binary log files can be
automatically removed. Possible removals happen at startup
and when the binary log is flushed. Log flushing occurs as
indicated in
<a class="xref" href="server-logs.html" title="7.4 MySQL Server Logs">
Section 7.4, “MySQL Server Logs”
</a>
.
</p>
<p>
The default binary log expiration period is 2592000 seconds,
which equals 30 days (30*24*60*60 seconds).
</p>
<p>
Automatic purging of the binary log can be disabled by
setting the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_expire_logs_auto_purge">
<code class="literal">
binlog_expire_logs_auto_purge
</code>
</a>
system variable to
<code class="literal">
OFF
</code>
. This takes
precedence over any setting for
<code class="literal">
binlog_expire_logs_seconds
</code>
.
</p>
<p>
To remove binary log files manually, use the
<a class="link" href="purge-binary-logs.html" title="15.4.1.1 PURGE BINARY LOGS Statement">
<code class="literal">
PURGE BINARY LOGS
</code>
</a>
statement.
See
<a class="xref" href="purge-binary-logs.html" title="15.4.1.1 PURGE BINARY LOGS Statement">
Section 15.4.1.1, “PURGE BINARY LOGS Statement”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_expire_logs_auto_purge">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_expire_logs_auto_purge">
<code class="literal">
binlog_expire_logs_auto_purge
</code>
</a>
</p>
<a class="indexterm" name="idm46045140439696">
</a>
<a class="indexterm" name="idm46045140438592">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_expire_logs_auto_purge">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-expire-logs-auto-purge={ON|OFF}
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_expire_logs_auto_purge">
binlog_expire_logs_auto_purge
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
ON
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Enables or disables automatic purging of binary log files.
Setting this variable to
<code class="literal">
ON
</code>
(the default)
enables automatic purging; setting it to
<code class="literal">
OFF
</code>
disables automatic purging. The
interval to wait before purging is controlled by
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_expire_logs_seconds">
<code class="literal">
binlog_expire_logs_seconds
</code>
</a>
.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Even if
<code class="literal">
binlog_expire_logs_auto_purge
</code>
is
<code class="literal">
ON
</code>
, setting
<code class="literal">
binlog_expire_logs_seconds
</code>
to
<code class="literal">
0
</code>
stops automatic purging from taking
place.
</p>
</div>
<p>
This variable has no effect on
<a class="link" href="purge-binary-logs.html" title="15.4.1.1 PURGE BINARY LOGS Statement">
<code class="literal">
PURGE
BINARY LOGS
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_format">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
</p>
<a class="indexterm" name="idm46045140405824">
</a>
<a class="indexterm" name="idm46045140404736">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_format">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-format=format
</code>
</td>
</tr>
<tr>
<th>
Deprecated
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
binlog_format
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global, Session
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Enumeration
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
ROW
</code>
</td>
</tr>
<tr>
<th>
Valid Values
</th>
<td>
<p class="valid-value">
<code class="literal">
MIXED
</code>
</p>
<p class="valid-value">
<code class="literal">
STATEMENT
</code>
</p>
<p class="valid-value">
<code class="literal">
ROW
</code>
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This system variable sets the binary logging format, and can
be any one of
<code class="literal">
STATEMENT
</code>
,
<code class="literal">
ROW
</code>
, or
<code class="literal">
MIXED
</code>
. (See
<a class="xref" href="replication-formats.html" title="19.2.1 Replication Formats">
Section 19.2.1, “Replication Formats”
</a>
.) The setting takes
effect when binary logging is enabled on the server, which
is the case when the
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin">
<code class="literal">
log_bin
</code>
</a>
system variable is
set to
<code class="literal">
ON
</code>
. In MySQL 8.4,
binary logging is enabled by default, and by default uses
the row-based format.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
<code class="literal">
binlog_format
</code>
is deprecated, and
subject to removal in a future version of MySQL. This
implies that support for logging formats other than
row-based is also subject to removal in a future release.
Thus, only row-based logging should be employed for any
new MySQL Replication setups.
</p>
</div>
<p>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
can be set at
startup or at runtime, except that under some conditions,
changing this variable at runtime is not possible or causes
replication to fail, as described later.
</p>
<p>
The default is
<code class="literal">
ROW
</code>
.
<span class="emphasis">
<em>
Exception
</em>
</span>
: In NDB Cluster, the default
is
<code class="literal">
MIXED
</code>
; statement-based replication is
not supported for NDB Cluster.
</p>
<p>
Setting the session value of this system variable is a
restricted operation. The session user must have privileges
sufficient to set restricted session variables. See
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
.
</p>
<p>
The rules governing when changes to this variable take
effect and how long the effect lasts are the same as for
other MySQL server system variables. For more information,
see
<a class="xref" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
Section 15.7.6.1, “SET Syntax for Variable Assignment”
</a>
.
</p>
<p>
When
<code class="literal">
MIXED
</code>
is specified, statement-based
replication is used, except for cases where only row-based
replication is guaranteed to lead to proper results. For
example, this happens when statements contain loadable
functions or the
<a class="link" href="miscellaneous-functions.html#function_uuid">
<code class="literal">
UUID()
</code>
</a>
function.
</p>
<p>
For details of how stored programs (stored procedures and
functions, triggers, and events) are handled when each
binary logging format is set, see
<a class="xref" href="stored-programs-logging.html" title="27.7 Stored Program Binary Logging">
Section 27.7, “Stored Program Binary Logging”
</a>
.
</p>
<p>
There are exceptions when you cannot switch the replication
format at runtime:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
The replication format cannot be changed from within a
stored function or a trigger.
</p>
</li>
<li class="listitem">
<p>
If a session has open temporary tables, the replication
format cannot be changed for the session (
<code class="literal">
SET
@@SESSION.binlog_format
</code>
).
</p>
</li>
<li class="listitem">
<p>
If any replication channel has open temporary tables,
the replication format cannot be changed globally
(
<code class="literal">
SET @@GLOBAL.binlog_format
</code>
or
<code class="literal">
SET @@PERSIST.binlog_format
</code>
).
</p>
</li>
<li class="listitem">
<p>
If any replication channel applier thread is currently
running, the replication format cannot be changed
globally (
<code class="literal">
SET @@GLOBAL.binlog_format
</code>
or
<code class="literal">
SET @@PERSIST.binlog_format
</code>
).
</p>
</li>
</ul>
</div>
<p>
Trying to switch the replication format in any of these
cases (or attempting to set the current replication format)
results in an error. You can, however, use
<code class="literal">
PERSIST_ONLY
</code>
(
<code class="literal">
SET
@@PERSIST_ONLY.binlog_format
</code>
) to change the
replication format at any time, because this action does not
modify the runtime global system variable value, and takes
effect only after a server restart.
</p>
<p>
Switching the replication format at runtime is not
recommended when any temporary tables exist, because
temporary tables are logged only when using statement-based
replication, whereas with row-based replication and mixed
replication, they are not logged.
</p>
<p>
Changing the logging format on a replication source server
does not cause a replica to change its logging format to
match. Switching the replication format while replication is
ongoing can cause issues if a replica has binary logging
enabled, and the change results in the replica using
<code class="literal">
STATEMENT
</code>
format logging while the source
is using
<code class="literal">
ROW
</code>
or
<code class="literal">
MIXED
</code>
format logging. A replica is not able to convert binary log
entries received in
<code class="literal">
ROW
</code>
logging format to
<code class="literal">
STATEMENT
</code>
format for use in its own
binary log, so this situation can cause replication to fail.
For more information, see
<a class="xref" href="binary-log-setting.html" title="7.4.4.2 Setting The Binary Log Format">
Section 7.4.4.2, “Setting The Binary Log Format”
</a>
.
</p>
<p>
The binary log format affects the behavior of the following
server options:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-do-db">
<code class="option">
--replicate-do-db
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replication-options-replica.html#option_mysqld_replicate-ignore-db">
<code class="option">
--replicate-ignore-db
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-do-db">
<code class="option">
--binlog-do-db
</code>
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replication-options-binary-log.html#option_mysqld_binlog-ignore-db">
<code class="option">
--binlog-ignore-db
</code>
</a>
</p>
</li>
</ul>
</div>
<p>
These effects are discussed in detail in the descriptions of
the individual options.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_group_commit_sync_delay">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_delay">
<code class="literal">
binlog_group_commit_sync_delay
</code>
</a>
</p>
<a class="indexterm" name="idm46045140331024">
</a>
<a class="indexterm" name="idm46045140329936">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_group_commit_sync_delay">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-group-commit-sync-delay=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_delay">
binlog_group_commit_sync_delay
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
0
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
0
</code>
</td>
</tr>
<tr>
<th>
Maximum Value
</th>
<td>
<code class="literal">
1000000
</code>
</td>
</tr>
<tr>
<th>
Unit
</th>
<td>
microseconds
</td>
</tr>
</tbody>
</table>
</div>
<p>
Controls how many microseconds the binary log commit waits
before synchronizing the binary log file to disk. By default
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_delay">
<code class="literal">
binlog_group_commit_sync_delay
</code>
</a>
is set to 0, meaning that there is no delay. Setting
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_delay">
<code class="literal">
binlog_group_commit_sync_delay
</code>
</a>
to a microsecond delay enables more transactions to be
synchronized together to disk at once, reducing the overall
time to commit a group of transactions because the larger
groups require fewer time units per group.
</p>
<p>
When
<a class="link" href="replication-options-binary-log.html#sysvar_sync_binlog">
<code class="literal">
sync_binlog=0
</code>
</a>
or
<a class="link" href="replication-options-binary-log.html#sysvar_sync_binlog">
<code class="literal">
sync_binlog=1
</code>
</a>
is set, the
delay specified by
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_delay">
<code class="literal">
binlog_group_commit_sync_delay
</code>
</a>
is applied for every binary log commit group before
synchronization (or in the case of
<a class="link" href="replication-options-binary-log.html#sysvar_sync_binlog">
<code class="literal">
sync_binlog=0
</code>
</a>
, before
proceeding). When
<a class="link" href="replication-options-binary-log.html#sysvar_sync_binlog">
<code class="literal">
sync_binlog
</code>
</a>
is set to a
value
<span class="emphasis">
<em>
n
</em>
</span>
greater than 1, the delay is
applied after every
<span class="emphasis">
<em>
n
</em>
</span>
binary log commit
groups.
</p>
<p>
Setting
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_delay">
<code class="literal">
binlog_group_commit_sync_delay
</code>
</a>
can increase the number of parallel committing transactions
on any server that has (or might have after a failover) a
replica, and therefore can increase parallel execution on
the replicas. To benefit from this effect, the replica
servers must have
<a class="link" href="replication-options-replica.html#sysvar_replica_parallel_type">
<code class="literal">
replica_parallel_type=LOGICAL_CLOCK
</code>
</a>
set. It is important to take into account both source and
replica throughput when you are setting
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_delay">
<code class="literal">
binlog_group_commit_sync_delay
</code>
</a>
.
</p>
<p>
Setting
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_delay">
<code class="literal">
binlog_group_commit_sync_delay
</code>
</a>
can also reduce the number of
<code class="literal">
fsync()
</code>
calls to the binary log on any server (source or replica)
that has a binary log.
</p>
<p>
Note that setting
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_delay">
<code class="literal">
binlog_group_commit_sync_delay
</code>
</a>
increases the latency of transactions on the server, which
might affect client applications. Also, on highly concurrent
workloads, it is possible for the delay to increase
contention and therefore reduce throughput. Typically, the
benefits of setting a delay outweigh the drawbacks, but
tuning should always be carried out to determine the optimal
setting.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_group_commit_sync_no_delay_count">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_no_delay_count">
<code class="literal">
binlog_group_commit_sync_no_delay_count
</code>
</a>
</p>
<a class="indexterm" name="idm46045140278208">
</a>
<a class="indexterm" name="idm46045140277120">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_group_commit_sync_no_delay_count">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-group-commit-sync-no-delay-count=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_no_delay_count">
binlog_group_commit_sync_no_delay_count
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
0
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
0
</code>
</td>
</tr>
<tr>
<th>
Maximum Value
</th>
<td>
<code class="literal">
100000
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The maximum number of transactions to wait for before
aborting the current delay as specified by
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_delay">
<code class="literal">
binlog_group_commit_sync_delay
</code>
</a>
.
If
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_group_commit_sync_delay">
<code class="literal">
binlog_group_commit_sync_delay
</code>
</a>
is set to 0, then this option has no effect.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_max_flush_queue_time">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_max_flush_queue_time">
<code class="literal">
binlog_max_flush_queue_time
</code>
</a>
</p>
<a class="indexterm" name="idm46045140244960">
</a>
<a class="indexterm" name="idm46045140243856">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_max_flush_queue_time">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-max-flush-queue-time=#
</code>
</td>
</tr>
<tr>
<th>
Deprecated
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_max_flush_queue_time">
binlog_max_flush_queue_time
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
0
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
0
</code>
</td>
</tr>
<tr>
<th>
Maximum Value
</th>
<td>
<code class="literal">
100000
</code>
</td>
</tr>
<tr>
<th>
Unit
</th>
<td>
microseconds
</td>
</tr>
</tbody>
</table>
</div>
<p>
<code class="literal">
binlog_max_flush_queue_time
</code>
is
deprecated, and is marked for eventual removal in a future
MySQL release. Formerly, this system variable controlled the
time in microseconds to continue reading transactions from
the flush queue before proceeding with group commit. It no
longer has any effect.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_order_commits">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_order_commits">
<code class="literal">
binlog_order_commits
</code>
</a>
</p>
<a class="indexterm" name="idm46045140209296">
</a>
<a class="indexterm" name="idm46045140208256">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_order_commits">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-order-commits[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_order_commits">
binlog_order_commits
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
ON
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
When this variable is enabled on a replication source server
(which is the default), transaction commit instructions
issued to storage engines are serialized on a single thread,
so that transactions are always committed in the same order
as they are written to the binary log. Disabling this
variable permits transaction commit instructions to be
issued using multiple threads. Used in combination with
binary log group commit, this prevents the commit rate of a
single transaction being a bottleneck to throughput, and
might therefore produce a performance improvement.
</p>
<p>
Transactions are written to the binary log at the point when
all the storage engines involved have confirmed that the
transaction is prepared to commit. The binary log group
commit logic then commits a group of transactions after
their binary log write has taken place. When
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_order_commits">
<code class="literal">
binlog_order_commits
</code>
</a>
is
disabled, because multiple threads are used for this
process, transactions in a commit group might be committed
in a different order from their order in the binary log.
(Transactions from a single client always commit in
chronological order.) In many cases this does not matter, as
operations carried out in separate transactions should
produce consistent results, and if that is not the case, a
single transaction ought to be used instead.
</p>
<p>
If you want to ensure that the transaction history on the
source and on a multithreaded replica remains identical, set
<a class="link" href="replication-options-replica.html#sysvar_replica_preserve_commit_order">
<code class="literal">
replica_preserve_commit_order=1
</code>
</a>
on the replica.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_rotate_encryption_master_key_at_startup">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_rotate_encryption_master_key_at_startup">
<code class="literal">
binlog_rotate_encryption_master_key_at_startup
</code>
</a>
</p>
<a class="indexterm" name="idm46045140177856">
</a>
<a class="indexterm" name="idm46045140176736">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_rotate_encryption_master_key_at_startup">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-rotate-encryption-master-key-at-startup[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_rotate_encryption_master_key_at_startup">
binlog_rotate_encryption_master_key_at_startup
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Specifies whether or not the binary log master key is
rotated at server startup. The binary log master key is the
binary log encryption key that is used to encrypt file
passwords for the binary log files and relay log files on
the server. When a server is started for the first time with
binary log encryption enabled
(
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_encryption">
<code class="literal">
binlog_encryption=ON
</code>
</a>
), a
new binary log encryption key is generated and used as the
binary log master key. If the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_rotate_encryption_master_key_at_startup">
<code class="literal">
binlog_rotate_encryption_master_key_at_startup
</code>
</a>
system variable is also set to
<code class="literal">
ON
</code>
,
whenever the server is restarted, a further binary log
encryption key is generated and used as the binary log
master key for all subsequent binary log files and relay log
files. If the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_rotate_encryption_master_key_at_startup">
<code class="literal">
binlog_rotate_encryption_master_key_at_startup
</code>
</a>
system variable is set to
<code class="literal">
OFF
</code>
, which is
the default, the existing binary log master key is used
again after the server restarts. For more information on
binary log encryption keys and the binary log master key,
see
<a class="xref" href="replication-binlog-encryption.html" title="19.3.2 Encrypting Binary Log Files and Relay Log Files">
Section 19.3.2, “Encrypting Binary Log Files and Relay Log Files”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_row_event_max_size">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_row_event_max_size">
<code class="literal">
binlog_row_event_max_size
</code>
</a>
</p>
<a class="indexterm" name="idm46045140145120">
</a>
<a class="indexterm" name="idm46045140144016">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog-row-event-max-size">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-row-event-max-size=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_row_event_max_size">
binlog_row_event_max_size
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
8192
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
256
</code>
</td>
</tr>
<tr>
<th>
Maximum Value (64-bit platforms)
</th>
<td>
<code class="literal">
18446744073709551615
</code>
</td>
</tr>
<tr>
<th>
Maximum Value (32-bit platforms)
</th>
<td>
<code class="literal">
4294967295
</code>
</td>
</tr>
<tr>
<th>
Unit
</th>
<td>
bytes
</td>
</tr>
</tbody>
</table>
</div>
<p>
When row-based binary logging is used, this setting is a
soft limit on the maximum size of a row-based binary log
event, in bytes. Where possible, rows stored in the binary
log are grouped into events with a size not exceeding the
value of this setting. If an event cannot be split, the
maximum size can be exceeded. The default is 8192 bytes.
</p>
<p>
This global system variable is read-only and can be set only
at server startup. Its value can therefore only be modified
by using the
<code class="literal">
PERSIST_ONLY
</code>
keyword or the
<code class="literal">
@@persist_only
</code>
qualifier with the
<a class="link" href="set.html" title="13.3.6 The SET Type">
<code class="literal">
SET
</code>
</a>
statement.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_row_image">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_row_image">
<code class="literal">
binlog_row_image
</code>
</a>
</p>
<a class="indexterm" name="idm46045140106528">
</a>
<a class="indexterm" name="idm46045140105440">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_row_image">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-row-image=image_type
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_row_image">
binlog_row_image
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global, Session
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Enumeration
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
full
</code>
</td>
</tr>
<tr>
<th>
Valid Values
</th>
<td>
<p class="valid-value">
<code class="literal">
full
</code>
(Log all columns)
</p>
<p class="valid-value">
<code class="literal">
minimal
</code>
(Log only changed columns, and columns needed to identify rows)
</p>
<p class="valid-value">
<code class="literal">
noblob
</code>
(Log all columns, except for unneeded BLOB and TEXT columns)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
For MySQL row-based replication, this variable determines
how row images are written to the binary log.
</p>
<p>
Setting the session value of this system variable is a
restricted operation. The session user must have privileges
sufficient to set restricted session variables. See
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
.
</p>
<p>
In MySQL row-based replication, each row change event
contains two images, a
<span class="quote">
“
<span class="quote">
before
</span>
”
</span>
image whose
columns are matched against when searching for the row to be
updated, and an
<span class="quote">
“
<span class="quote">
after
</span>
”
</span>
image containing the
changes. Normally, MySQL logs full rows (that is, all
columns) for both the before and after images. However, it
is not strictly necessary to include every column in both
images, and we can often save disk, memory, and network
usage by logging only those columns which are actually
required.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
When deleting a row, only the before image is logged,
since there are no changed values to propagate following
the deletion. When inserting a row, only the after image
is logged, since there is no existing row to be matched.
Only when updating a row are both the before and after
images required, and both written to the binary log.
</p>
</div>
<p>
For the before image, it is necessary only that the minimum
set of columns required to uniquely identify rows is logged.
If the table containing the row has a primary key, then only
the primary key column or columns are written to the binary
log. Otherwise, if the table has a unique key all of whose
columns are
<code class="literal">
NOT NULL
</code>
, then only the
columns in the unique key need be logged. (If the table has
neither a primary key nor a unique key without any
<code class="literal">
NULL
</code>
columns, then all columns must be
used in the before image, and logged.) In the after image,
it is necessary to log only the columns which have actually
changed.
</p>
<p>
You can cause the server to log full or minimal rows using
the
<code class="literal">
binlog_row_image
</code>
system variable.
This variable actually takes one of three possible values,
as shown in the following list:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
full
</code>
: Log all columns in both the
before image and the after image.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
minimal
</code>
: Log only those columns in
the before image that are required to identify the row
to be changed; log only those columns in the after image
where a value was specified by the SQL statement, or
generated by auto-increment.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
noblob
</code>
: Log all columns (same as
<code class="literal">
full
</code>
), except for
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
and
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
columns that are not
required to identify rows, or that have not changed.
</p>
</li>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
This variable is not supported by NDB Cluster; setting it
has no effect on the logging of
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
tables.
</p>
</div>
<p>
The default value is
<code class="literal">
full
</code>
.
</p>
<p>
When using
<code class="literal">
minimal
</code>
or
<code class="literal">
noblob
</code>
, deletes and updates are
guaranteed to work correctly for a given table if and only
if the following conditions are true for both the source and
destination tables:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
All columns must be present and in the same order; each
column must use the same data type as its counterpart in
the other table.
</p>
</li>
<li class="listitem">
<p>
The tables must have identical primary key definitions.
</p>
</li>
</ul>
</div>
<p>
(In other words, the tables must be identical with the
possible exception of indexes that are not part of the
tables' primary keys.)
</p>
<p>
If these conditions are not met, it is possible that the
primary key column values in the destination table may prove
insufficient to provide a unique match for a delete or
update. In this event, no warning or error is issued; the
source and replica silently diverge, thus breaking
consistency.
</p>
<p>
Setting this variable has no effect when the binary logging
format is
<code class="literal">
STATEMENT
</code>
. When
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
is
<code class="literal">
MIXED
</code>
, the setting for
<code class="literal">
binlog_row_image
</code>
is applied to changes
that are logged using row-based format, but this setting has
no effect on changes logged as statements.
</p>
<p>
Setting
<code class="literal">
binlog_row_image
</code>
on either the
global or session level does not cause an implicit commit;
this means that this variable can be changed while a
transaction is in progress without affecting the
transaction.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_row_metadata">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_row_metadata">
<code class="literal">
binlog_row_metadata
</code>
</a>
</p>
<a class="indexterm" name="idm46045140044288">
</a>
<a class="indexterm" name="idm46045140043248">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_row_metadata">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-row-metadata=metadata_type
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_row_metadata">
binlog_row_metadata
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Enumeration
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
MINIMAL
</code>
</td>
</tr>
<tr>
<th>
Valid Values
</th>
<td>
<p class="valid-value">
<code class="literal">
FULL
</code>
(All metadata is included)
</p>
<p class="valid-value">
<code class="literal">
MINIMAL
</code>
(Limit included metadata)
</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Configures the amount of table metadata added to the binary
log when using row-based logging. When set to
<code class="literal">
MINIMAL
</code>
, the default, only metadata
related to
<code class="literal">
SIGNED
</code>
flags, column character
set and geometry types are logged. When set to
<code class="literal">
FULL
</code>
complete metadata for tables is
logged, such as column name,
<a class="link" href="enum.html" title="13.3.5 The ENUM Type">
<code class="literal">
ENUM
</code>
</a>
or
<code class="literal">
SET
</code>
string values,
<code class="literal">
PRIMARY
KEY
</code>
information, and so on.
</p>
<p>
The extended metadata serves the following purposes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Replicas use the metadata to transfer data when its
table structure is different from the source's.
</p>
</li>
<li class="listitem">
<p>
External software can use the metadata to decode row
events and store the data into external databases, such
as a data warehouse.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_row_value_options">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_row_value_options">
<code class="literal">
binlog_row_value_options
</code>
</a>
</p>
<a class="indexterm" name="idm46045140006704">
</a>
<a class="indexterm" name="idm46045140005600">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_row_value_options">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-row-value-options=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_row_value_options">
binlog_row_value_options
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global, Session
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Set
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
</code>
</td>
</tr>
<tr>
<th>
Valid Values
</th>
<td>
<code class="literal">
PARTIAL_JSON
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
When set to
<code class="literal">
PARTIAL_JSON
</code>
, this enables
use of a space-efficient binary log format for updates that
modify only a small portion of a JSON document, which causes
row-based replication to write only the modified parts of
the JSON document to the after-image for the update in the
binary log, rather than writing the full document (see
<a class="xref" href="json.html#json-partial-updates" title="Partial Updates of JSON Values">
Partial Updates of JSON Values
</a>
). This works for an
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
statement which
modifies a JSON column using any sequence of
<a class="link" href="json-modification-functions.html#function_json-set">
<code class="literal">
JSON_SET()
</code>
</a>
,
<a class="link" href="json-modification-functions.html#function_json-replace">
<code class="literal">
JSON_REPLACE()
</code>
</a>
, and
<a class="link" href="json-modification-functions.html#function_json-remove">
<code class="literal">
JSON_REMOVE()
</code>
</a>
. If the server
is unable to generate a partial update, the full document is
used instead.
</p>
<p>
The default value is an empty string, which disables use of
the format. To unset
<code class="literal">
binlog_row_value_options
</code>
and revert to
writing the full JSON document, set its value to the empty
string.
</p>
<p>
Setting the session value of this system variable is a
restricted operation. The session user must have privileges
sufficient to set restricted session variables. See
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
.
</p>
<p>
<code class="literal">
binlog_row_value_options=PARTIAL_JSON
</code>
takes effect only when binary logging is enabled and
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="literal">
binlog_format
</code>
</a>
is set to
<code class="literal">
ROW
</code>
or
<code class="literal">
MIXED
</code>
.
Statement-based replication
<span class="emphasis">
<em>
always
</em>
</span>
logs
only the modified parts of the JSON document, regardless of
any value set for
<code class="literal">
binlog_row_value_options
</code>
. To maximize the
amount of space saved, use
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_row_image">
<code class="literal">
binlog_row_image=NOBLOB
</code>
</a>
or
<code class="literal">
binlog_row_image=MINIMAL
</code>
together with
this option.
<code class="literal">
binlog_row_image=FULL
</code>
saves
less space than either of these, since the full JSON
document is stored in the before-image, and the partial
update is stored only in the after-image.
</p>
<p>
<a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
<span class="command">
<strong>
mysqlbinlog
</strong>
</span>
</a>
output includes partial JSON
updates in the form of events encoded as base-64 strings
using
<a class="link" href="binlog.html" title="15.7.8.1 BINLOG Statement">
<code class="literal">
BINLOG
</code>
</a>
statements. If
the
<a class="link" href="mysqlbinlog.html#option_mysqlbinlog_verbose">
<code class="option">
--verbose
</code>
</a>
option is
specified,
<a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
<span class="command">
<strong>
mysqlbinlog
</strong>
</span>
</a>
displays the
partial JSON updates as readable JSON using pseudo-SQL
statements.
</p>
<p>
MySQL Replication generates an error if a modification
cannot be applied to the JSON document on the replica. This
includes a failure to find the path. Be aware that, even
with this and other safety checks, if a JSON document on a
replica has diverged from that on the source and a partial
update is applied, it remains theoretically possible to
produce a valid but unexpected JSON document on the replica.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_rows_query_log_events">
</a>
<code class="literal">
binlog_rows_query_log_events
</code>
</p>
<a class="indexterm" name="idm46045139954656">
</a>
<a class="indexterm" name="idm46045139953552">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_rows_query_log_events">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-rows-query-log-events[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_rows_query_log_events">
binlog_rows_query_log_events
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global, Session
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This system variable affects row-based logging only. When
enabled, it causes the server to write informational log
events such as row query log events into its binary log.
This information can be used for debugging and related
purposes, such as obtaining the original query issued on the
source when it cannot be reconstructed from the row updates.
</p>
<p>
Setting the session value of this system variable is a
restricted operation. The session user must have privileges
sufficient to set restricted session variables. See
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
.
</p>
<p>
These informational events are normally ignored by MySQL
programs reading the binary log and so cause no issues when
replicating or restoring from backup. To view them, increase
the verbosity level by using mysqlbinlog's
<a class="link" href="mysqlbinlog.html#option_mysqlbinlog_verbose">
<code class="option">
--verbose
</code>
</a>
option twice,
either as
<code class="option">
-vv
</code>
or
<code class="option">
--verbose
--verbose
</code>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_stmt_cache_size">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_stmt_cache_size">
<code class="literal">
binlog_stmt_cache_size
</code>
</a>
</p>
<a class="indexterm" name="idm46045139924608">
</a>
<a class="indexterm" name="idm46045139923568">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_stmt_cache_size">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-stmt-cache-size=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_stmt_cache_size">
binlog_stmt_cache_size
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
32768
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
4096
</code>
</td>
</tr>
<tr>
<th>
Maximum Value (64-bit platforms)
</th>
<td>
<code class="literal">
18446744073709547520
</code>
</td>
</tr>
<tr>
<th>
Maximum Value (32-bit platforms)
</th>
<td>
<code class="literal">
4294963200
</code>
</td>
</tr>
<tr>
<th>
Unit
</th>
<td>
bytes
</td>
</tr>
<tr>
<th>
<a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
Block Size
</a>
</th>
<td>
<code class="literal">
4096
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
The size of the memory buffer for the binary log to hold
nontransactional statements issued during a transaction.
</p>
<p>
When binary logging is enabled on the server (with the
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin">
<code class="literal">
log_bin
</code>
</a>
system variable set
to ON), separate binary log transaction and statement caches
are allocated for each client if the server supports any
transactional storage engines. If the data for the
nontransactional statements used in the transaction exceeds
the space in the memory buffer, the excess data is stored in
a temporary file. When binary log encryption is active on
the server, the memory buffer is not encrypted, but any
temporary file used to hold the binary log cache is
encrypted. After each transaction is committed, the binary
log statement cache is reset by clearing the memory buffer
and truncating the temporary file if used.
</p>
<p>
If you often use large nontransactional statements during
transactions, you can increase this cache size to get better
performance by reducing or eliminating the need to write to
temporary files. The
<a class="link" href="server-status-variables.html#statvar_Binlog_stmt_cache_use">
<code class="literal">
Binlog_stmt_cache_use
</code>
</a>
and
<a class="link" href="server-status-variables.html#statvar_Binlog_stmt_cache_disk_use">
<code class="literal">
Binlog_stmt_cache_disk_use
</code>
</a>
status variables can be useful for tuning the size of this
variable. See
<a class="xref" href="binary-log.html" title="7.4.4 The Binary Log">
Section 7.4.4, “The Binary Log”
</a>
.
</p>
<p>
The
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_cache_size">
<code class="literal">
binlog_cache_size
</code>
</a>
system variable sets the size for the transaction cache.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_transaction_compression">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_compression">
<code class="literal">
binlog_transaction_compression
</code>
</a>
</p>
<a class="indexterm" name="idm46045139877504">
</a>
<a class="indexterm" name="idm46045139876400">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_transaction_compression">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-transaction-compression[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_compression">
binlog_transaction_compression
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global, Session
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Enables compression for transactions that are written to
binary log files on this server.
<code class="literal">
OFF
</code>
is
the default. Use the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_compression_level_zstd">
<code class="literal">
binlog_transaction_compression_level_zstd
</code>
</a>
system variable to set the level for the
<code class="literal">
zstd
</code>
algorithm that is used for
compression.
</p>
<p>
Setting
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_compression">
<code class="literal">
binlog_transaction_compression
</code>
</a>
has no immediate effect but rather applies to all subsequent
<a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement">
<code class="literal">
START REPLICA
</code>
</a>
statements.
</p>
<p>
When binary log transaction compression is enabled,
transaction payloads are compressed and then written to the
binary log file as a single event
(
<code class="literal">
Transaction_payload_event
</code>
). Compressed
transaction payloads remain in a compressed state while they
are sent in the replication stream to replicas, other Group
Replication group members, or clients such as
<a class="link" href="mysqlbinlog.html" title="6.6.9 mysqlbinlog — Utility for Processing Binary Log Files">
<span class="command">
<strong>
mysqlbinlog
</strong>
</span>
</a>
, and are written to the relay
log still in their compressed state. Binary log transaction
compression therefore saves storage space both on the
originator of the transaction and on the recipient (and for
their backups), and saves network bandwidth when the
transactions are sent between server instances.
</p>
<p>
For
<code class="literal">
binlog_transaction_compression=ON
</code>
to
have a direct effect, binary logging must be enabled on the
server. When a MySQL 8.4 server instance has no
binary log, it can receive, handle, and display compressed
transaction payloads regardless of its value for
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_compression">
<code class="literal">
binlog_transaction_compression
</code>
</a>
.
Compressed transaction payloads received by such server
instances are written in their compressed state to the relay
log, so they benefit indirectly from compression carried out
by other servers in the replication topology.
</p>
<p>
This system variable cannot be changed within the context of
a transaction. Setting the session value of this system
variable is a restricted operation. The session user must
have privileges sufficient to set restricted session
variables. See
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
.
</p>
<p>
For more information on binary log transaction compression,
including details of what events are and are not compressed,
and changes in behavior when transaction compression is in
use, see
<a class="xref" href="binary-log-transaction-compression.html" title="7.4.4.5 Binary Log Transaction Compression">
Section 7.4.4.5, “Binary Log Transaction Compression”
</a>
.
</p>
<p>
You can use the
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_transaction_compression">
<code class="literal">
ndb_log_transaction_compression
</code>
</a>
system variable to enable this feature for
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
. In addition, setting
<code class="option">
--binlog-transaction-compression=ON
</code>
on the
command line or in a
<code class="filename">
my.cnf
</code>
file causes
<code class="literal">
ndb_log_transaction_compression
</code>
to be
enabled on server startup. See the description of the
variable for further information.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_transaction_compression_level_zstd">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_compression_level_zstd">
<code class="literal">
binlog_transaction_compression_level_zstd
</code>
</a>
</p>
<a class="indexterm" name="idm46045139831872">
</a>
<a class="indexterm" name="idm46045139830752">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_transaction_compression_level_zstd">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-transaction-compression-level-zstd=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_compression_level_zstd">
binlog_transaction_compression_level_zstd
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global, Session
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
3
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
1
</code>
</td>
</tr>
<tr>
<th>
Maximum Value
</th>
<td>
<code class="literal">
22
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Sets the compression level for binary log transaction
compression on this server, which is enabled by the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_compression">
<code class="literal">
binlog_transaction_compression
</code>
</a>
system variable. The value is an integer that determines the
compression effort, from 1 (the lowest effort) to 22 (the
highest effort). If you do not specify this system variable,
the compression level is set to 3.
</p>
<p>
Setting
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_compression_level_zstd">
<code class="literal">
binlog_transaction_compression_level_zstd
</code>
</a>
has no immediate effect but rather applies to all subsequent
<a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement">
<code class="literal">
START REPLICA
</code>
</a>
statements.
</p>
<p>
As the compression level increases, the data compression
ratio increases, which reduces the storage space and network
bandwidth required for the transaction payload. However, the
effort required for data compression also increases, taking
time and CPU and memory resources on the originating server.
Increases in the compression effort do not have a linear
relationship to increases in the data compression ratio.
</p>
<p>
This system variable cannot be changed within the context of
a transaction. Setting the session value of this system
variable is a restricted operation. The session user must
have privileges sufficient to set restricted session
variables. See
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
.
</p>
<p>
This variable has no effect on logging of transactions on
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
tables; use
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_transaction_compression_level_zstd">
<code class="literal">
ndb_log_transaction_compression_level_zstd
</code>
</a>
instead.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_binlog_transaction_dependency_history_size">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_dependency_history_size">
<code class="literal">
binlog_transaction_dependency_history_size
</code>
</a>
</p>
<a class="indexterm" name="idm46045139791152">
</a>
<a class="indexterm" name="idm46045139790032">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for binlog_transaction_dependency_history_size">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--binlog-transaction-dependency-history-size=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_transaction_dependency_history_size">
binlog_transaction_dependency_history_size
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
25000
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
1
</code>
</td>
</tr>
<tr>
<th>
Maximum Value
</th>
<td>
<code class="literal">
1000000
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Sets an upper limit on the number of row hashes which are
kept in memory and used for looking up the transaction that
last modified a given row. Once this number of hashes has
been reached, the history is purged.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_log_bin">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin">
<code class="literal">
log_bin
</code>
</a>
</p>
<a class="indexterm" name="idm46045139760352">
</a>
<a class="indexterm" name="idm46045139759280">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for log_bin">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin">
log_bin
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
</tbody>
</table>
</div>
<p>
Shows the status of binary logging on the server, either
enabled (
<code class="literal">
ON
</code>
) or disabled
(
<code class="literal">
OFF
</code>
). With binary logging enabled, the
server logs all statements that change data to the binary
log, which is used for backup and replication.
<code class="literal">
ON
</code>
means that the binary log is
available,
<code class="literal">
OFF
</code>
means that it is not in
use. The
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--log-bin
</code>
</a>
option can
be used to specify a base name and location for the binary
log.
</p>
<p>
In earlier MySQL versions, binary logging was disabled by
default, and was enabled if you specified the
<code class="option">
--log-bin
</code>
option. Binary logging is enabled
by default, with the
<code class="literal">
log_bin
</code>
system
variable set to
<code class="literal">
ON
</code>
, whether or not you
specify the
<code class="option">
--log-bin
</code>
option. The exception
is if you use
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
to initialize the
data directory manually by invoking it with the
<code class="option">
--initialize
</code>
or
<code class="option">
--initialize-insecure
</code>
option, when binary
logging is disabled by default. It is possible to enable
binary logging in this case by specifying the
<code class="option">
--log-bin
</code>
option.
</p>
<p>
If the
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--skip-log-bin
</code>
</a>
or
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--disable-log-bin
</code>
</a>
option is specified at startup, binary logging is disabled,
with the
<code class="literal">
log_bin
</code>
system variable set to
<code class="literal">
OFF
</code>
. If either of these options is
specified and
<code class="option">
--log-bin
</code>
is also specified,
the option specified later takes precedence.
</p>
<p>
For information on the format and management of the binary
log, see
<a class="xref" href="binary-log.html" title="7.4.4 The Binary Log">
Section 7.4.4, “The Binary Log”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_log_bin_basename">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin_basename">
<code class="literal">
log_bin_basename
</code>
</a>
</p>
<a class="indexterm" name="idm46045139724320">
</a>
<a class="indexterm" name="idm46045139723232">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for log_bin_basename">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin_basename">
log_bin_basename
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
File name
</td>
</tr>
</tbody>
</table>
</div>
<p>
Holds the base name and path for the binary log files, which
can be set with the
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--log-bin
</code>
</a>
server option. The maximum variable length is 256. In MySQL
8.4, if the
<code class="option">
--log-bin
</code>
option
is not supplied, the default base name is
<code class="filename">
binlog
</code>
. For compatibility with MySQL
5.7, if the
<code class="option">
--log-bin
</code>
option is supplied
with no string or with an empty string, the default base
name is
<code class="filename">
<em class="replaceable">
<code>
host_name
</code>
</em>
-bin
</code>
,
using the name of the host machine. The default location is
the data directory.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_log_bin_index">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin_index">
<code class="literal">
log_bin_index
</code>
</a>
</p>
<a class="indexterm" name="idm46045139699168">
</a>
<a class="indexterm" name="idm46045139698080">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for log-bin-index">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--log-bin-index=file_name
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin_index">
log_bin_index
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
File name
</td>
</tr>
</tbody>
</table>
</div>
<p>
Holds the base name and path for the binary log index file,
which can be set with the
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin-index">
<code class="option">
--log-bin-index
</code>
</a>
server
option. The maximum variable length is 256.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_log_bin_trust_function_creators">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin_trust_function_creators">
<code class="literal">
log_bin_trust_function_creators
</code>
</a>
</p>
<a class="indexterm" name="idm46045139674896">
</a>
<a class="indexterm" name="idm46045139673792">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for log_bin_trust_function_creators">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--log-bin-trust-function-creators[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
Deprecated
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin_trust_function_creators">
log_bin_trust_function_creators
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This variable applies when binary logging is enabled. It
controls whether stored function creators can be trusted not
to create stored functions that may cause unsafe events to
be written to the binary log. If set to 0 (the default),
users are not permitted to create or alter stored functions
unless they have the
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege in addition to the
<a class="link" href="privileges-provided.html#priv_create-routine">
<code class="literal">
CREATE
ROUTINE
</code>
</a>
or
<a class="link" href="privileges-provided.html#priv_alter-routine">
<code class="literal">
ALTER
ROUTINE
</code>
</a>
privilege. A setting of 0 also enforces
the restriction that a function must be declared with the
<code class="literal">
DETERMINISTIC
</code>
characteristic, or with the
<code class="literal">
READS SQL DATA
</code>
or
<code class="literal">
NO
SQL
</code>
characteristic. If the variable is set to 1,
MySQL does not enforce these restrictions on stored function
creation. This variable also applies to trigger creation.
See
<a class="xref" href="stored-programs-logging.html" title="27.7 Stored Program Binary Logging">
Section 27.7, “Stored Program Binary Logging”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_log_replica_updates">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="literal">
log_replica_updates
</code>
</a>
</p>
<a class="indexterm" name="idm46045139639920">
</a>
<a class="indexterm" name="idm46045139638880">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for log_replica_updates">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--log-replica-updates[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
log_replica_updates
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
ON
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="literal">
log_replica_updates
</code>
</a>
specifies whether updates received by a replica server from
a replication source server should be logged to the
replica's own binary log.
</p>
<p>
Enabling this variable causes the replica to write the
updates that are received from a source and performed by the
replication SQL thread to the replica's own binary log.
Binary logging, which is controlled by the
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--log-bin
</code>
</a>
option and is
enabled by default, must also be enabled on the replica for
updates to be logged. See
<a class="xref" href="replication-options.html" title="19.1.6 Replication and Binary Logging Options and Variables">
Section 19.1.6, “Replication and Binary Logging Options and Variables”
</a>
.
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="literal">
log_replica_updates
</code>
</a>
is
enabled by default, unless you specify
<a class="link" href="replication-options-binary-log.html#option_mysqld_log-bin">
<code class="option">
--skip-log-bin
</code>
</a>
to disable binary logging, in which case MySQL also disables
replica update logging by default. If you need to disable
replica update logging when binary logging is enabled,
specify
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="option">
--log-replica-updates=OFF
</code>
</a>
at
replica server startup.
</p>
<p>
Enabling
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="literal">
log_replica_updates
</code>
</a>
enables
replication servers to be chained. For example, you might
want to set up replication servers using this arrangement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-none"><div class="docs-select-all right" id="sa99277481"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">A -> B -> C</code></pre>
</div>
<p>
Here,
<code class="literal">
A
</code>
serves as the source for the
replica
<code class="literal">
B
</code>
, and
<code class="literal">
B
</code>
serves as the source for the replica
<code class="literal">
C
</code>
.
For this to work,
<code class="literal">
B
</code>
must be both a source
<span class="emphasis">
<em>
and
</em>
</span>
a replica. With binary logging
enabled and
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="literal">
log_replica_updates
</code>
</a>
enabled, which are the default settings, updates received
from
<code class="literal">
A
</code>
are logged by
<code class="literal">
B
</code>
to its binary log, and can therefore be passed on to
<code class="literal">
C
</code>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_log_slave_updates">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_log_slave_updates">
<code class="literal">
log_slave_updates
</code>
</a>
</p>
<a class="indexterm" name="idm46045139596240">
</a>
<a class="indexterm" name="idm46045139595200">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for log_slave_updates">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--log-slave-updates[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
Deprecated
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_log_slave_updates">
log_slave_updates
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
No
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
ON
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Deprecated alias for
<a class="link" href="replication-options-binary-log.html#sysvar_log_replica_updates">
<code class="literal">
log_replica_updates
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_log_statements_unsafe_for_binlog">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_log_statements_unsafe_for_binlog">
<code class="literal">
log_statements_unsafe_for_binlog
</code>
</a>
</p>
<a class="indexterm" name="idm46045139567360">
</a>
<a class="indexterm" name="idm46045139566256">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for log_statements_unsafe_for_binlog">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--log-statements-unsafe-for-binlog[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
Deprecated
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_log_statements_unsafe_for_binlog">
log_statements_unsafe_for_binlog
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
ON
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
If error 1592 is encountered, controls whether the generated
warnings are added to the error log or not.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_master_verify_checksum">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_master_verify_checksum">
<code class="literal">
master_verify_checksum
</code>
</a>
</p>
<a class="indexterm" name="idm46045139539552">
</a>
<a class="indexterm" name="idm46045139538512">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for master_verify_checksum">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--master-verify-checksum[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
Deprecated
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_master_verify_checksum">
master_verify_checksum
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Deprecated alias for
<a class="link" href="replication-options-binary-log.html#sysvar_source_verify_checksum">
<code class="literal">
source_verify_checksum
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_max_binlog_cache_size">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_cache_size">
<code class="literal">
max_binlog_cache_size
</code>
</a>
</p>
<a class="indexterm" name="idm46045139510704">
</a>
<a class="indexterm" name="idm46045139509664">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for max_binlog_cache_size">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--max-binlog-cache-size=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_cache_size">
max_binlog_cache_size
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value (64-bit platforms)
</th>
<td>
<code class="literal">
18446744073709547520
</code>
</td>
</tr>
<tr>
<th>
Default Value (32-bit platforms)
</th>
<td>
<code class="literal">
4294967295
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
4096
</code>
</td>
</tr>
<tr>
<th>
Maximum Value (64-bit platforms)
</th>
<td>
<code class="literal">
18446744073709547520
</code>
</td>
</tr>
<tr>
<th>
Maximum Value (32-bit platforms)
</th>
<td>
<code class="literal">
4294967295
</code>
</td>
</tr>
<tr>
<th>
Unit
</th>
<td>
bytes
</td>
</tr>
<tr>
<th>
<a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
Block Size
</a>
</th>
<td>
<code class="literal">
4096
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
If a transaction requires more than this many bytes, the
server generates a
<span class="errortext">
Multi-statement transaction
required more than 'max_binlog_cache_size' bytes of
storage
</span>
error. When
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
is not
<code class="literal">
ON
</code>
, the maximum recommended value is 4GB,
due to the fact that, in this case, MySQL cannot work with
binary log positions greater than 4GB; when
<code class="literal">
gtid_mode
</code>
is
<code class="literal">
ON
</code>
, this
limitation does not apply, and the server can work with
binary log positions of arbitrary size.
</p>
<p>
If, because
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
is
not
<code class="literal">
ON
</code>
, or for some other reason, you
need to guarantee that the binary log does not exceed a
given size
<em class="replaceable">
<code>
maxsize
</code>
</em>
, you should
set this variable according to the formula shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-simple"><div class="docs-select-all right" id="sa68218065"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">max_binlog_cache_size <span class="token operator"><</span>
<span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">(</span><em class="replaceable">maxsize</em> <span class="token operator">-</span> max_binlog_size<span class="token punctuation">)</span> <span class="token operator">/</span> max_connections<span class="token punctuation">)</span> <span class="token operator">-</span> 1000<span class="token punctuation">)</span> <span class="token operator">/</span> 1<span class="token punctuation">.</span>2</code></pre>
</div>
<p>
This calculation takes into account the following
conditions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
The server writes to the binary log as long as the size
before it begins to write is less than
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_size">
<code class="literal">
max_binlog_size
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
The server does not write single transactions, but
rather groups of transactions. The maximum possible
number of transactions in a group is equal to
<a class="link" href="server-system-variables.html#sysvar_max_connections">
<code class="literal">
max_connections
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
The server writes data that is not included in the
cache. This includes a 4-byte checksum for each event;
while this adds less than 20% to the transaction size,
this amount is non-negible. In addition, the server
writes a
<code class="literal">
Gtid_log_event
</code>
for each
transaction; each of these events can add another 1 KB
to what is written to the binary log.
</p>
</li>
</ul>
</div>
<p>
<code class="literal">
max_binlog_cache_size
</code>
sets the size for
the transaction cache only; the upper limit for the
statement cache is governed by the
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_stmt_cache_size">
<code class="literal">
max_binlog_stmt_cache_size
</code>
</a>
system variable.
</p>
<p>
The visibility to sessions of
<code class="literal">
max_binlog_cache_size
</code>
matches that of the
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_cache_size">
<code class="literal">
binlog_cache_size
</code>
</a>
system
variable; in other words, changing its value affects only
new sessions that are started after the value is changed.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_max_binlog_size">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_size">
<code class="literal">
max_binlog_size
</code>
</a>
</p>
<a class="indexterm" name="idm46045139446896">
</a>
<a class="indexterm" name="idm46045139445808">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for max_binlog_size">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--max-binlog-size=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_size">
max_binlog_size
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
1073741824
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
4096
</code>
</td>
</tr>
<tr>
<th>
Maximum Value
</th>
<td>
<code class="literal">
1073741824
</code>
</td>
</tr>
<tr>
<th>
Unit
</th>
<td>
bytes
</td>
</tr>
<tr>
<th>
<a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
Block Size
</a>
</th>
<td>
<code class="literal">
4096
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
If a write to the binary log causes the current log file
size to exceed the value of this variable, the server
rotates the binary logs (closes the current file and opens
the next one). The minimum value is 4096 bytes. The maximum
and default value is 1GB. Encrypted binary log files have an
additional 512-byte header, which is included in
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_size">
<code class="literal">
max_binlog_size
</code>
</a>
.
</p>
<p>
A transaction is written in one chunk to the binary log, so
it is never split between several binary logs. Therefore, if
you have big transactions, you might see binary log files
larger than
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_size">
<code class="literal">
max_binlog_size
</code>
</a>
.
</p>
<p>
If
<a class="link" href="replication-options-replica.html#sysvar_max_relay_log_size">
<code class="literal">
max_relay_log_size
</code>
</a>
is 0,
the value of
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_size">
<code class="literal">
max_binlog_size
</code>
</a>
applies to
relay logs as well.
</p>
<p>
With GTIDs in use on the server, when
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_size">
<code class="literal">
max_binlog_size
</code>
</a>
is reached,
if the system table
<code class="literal">
mysql.gtid_executed
</code>
cannot be accessed to write the GTIDs from the current
binary log file, the binary log cannot be rotated. In this
situation, the server responds according to its
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_error_action">
<code class="literal">
binlog_error_action
</code>
</a>
setting. If
<code class="literal">
IGNORE_ERROR
</code>
is set, an error
is logged on the server and binary logging is halted, or if
<code class="literal">
ABORT_SERVER
</code>
is set, the server shuts
down.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_max_binlog_stmt_cache_size">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_stmt_cache_size">
<code class="literal">
max_binlog_stmt_cache_size
</code>
</a>
</p>
<a class="indexterm" name="idm46045139399440">
</a>
<a class="indexterm" name="idm46045139398336">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for max_binlog_stmt_cache_size">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--max-binlog-stmt-cache-size=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_stmt_cache_size">
max_binlog_stmt_cache_size
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
18446744073709547520
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
4096
</code>
</td>
</tr>
<tr>
<th>
Maximum Value
</th>
<td>
<code class="literal">
18446744073709547520
</code>
</td>
</tr>
<tr>
<th>
Unit
</th>
<td>
bytes
</td>
</tr>
<tr>
<th>
<a class="link" href="server-system-variables.html#system-variables-block-size" title="Note">
Block Size
</a>
</th>
<td>
<code class="literal">
4096
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
If nontransactional statements within a transaction require
more than this many bytes of memory, the server generates an
error. The minimum value is 4096. The maximum and default
values are 4GB on 32-bit platforms and 16EB (exabytes) on
64-bit platforms.
</p>
<p>
<code class="literal">
max_binlog_stmt_cache_size
</code>
sets the size
for the statement cache only; the upper limit for the
transaction cache is governed exclusively by the
<a class="link" href="replication-options-binary-log.html#sysvar_max_binlog_cache_size">
<code class="literal">
max_binlog_cache_size
</code>
</a>
system variable.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_original_commit_timestamp">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_original_commit_timestamp">
<code class="literal">
original_commit_timestamp
</code>
</a>
</p>
<a class="indexterm" name="idm46045139360592">
</a>
<a class="indexterm" name="idm46045139359488">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for original_commit_timestamp">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_original_commit_timestamp">
original_commit_timestamp
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Session
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Numeric
</td>
</tr>
</tbody>
</table>
</div>
<p>
For internal use by replication. When re-executing a
transaction on a replica, this is set to the time when the
transaction was committed on the original source, measured
in microseconds since the epoch. This allows the original
commit timestamp to be propagated throughout a replication
topology.
</p>
<p>
Setting the session value of this system variable is a
restricted operation. The session user must have either the
<a class="link" href="privileges-provided.html#priv_replication-applier">
<code class="literal">
REPLICATION_APPLIER
</code>
</a>
privilege
(see
<a class="xref" href="replication-privilege-checks.html" title="19.3.3 Replication Privilege Checks">
Section 19.3.3, “Replication Privilege Checks”
</a>
), or
privileges sufficient to set restricted session variables
(see
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
). However,
note that the variable is not intended for users to set; it
is set automatically by the replication infrastructure.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_source_verify_checksum">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_source_verify_checksum">
<code class="literal">
source_verify_checksum
</code>
</a>
</p>
<a class="indexterm" name="idm46045139335984">
</a>
<a class="indexterm" name="idm46045139334944">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for source_verify_checksum">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--source-verify-checksum[={OFF|ON}]
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_source_verify_checksum">
source_verify_checksum
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
OFF
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Enabling
<a class="link" href="replication-options-binary-log.html#sysvar_source_verify_checksum">
<code class="literal">
source_verify_checksum
</code>
</a>
causes the source to verify events read from the binary log
by examining checksums, and to stop with an error in the
event of a mismatch.
<a class="link" href="replication-options-binary-log.html#sysvar_source_verify_checksum">
<code class="literal">
source_verify_checksum
</code>
</a>
is
disabled by default; in this case, the source uses the event
length from the binary log to verify events, so that only
complete events are read from the binary log.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_sql_log_bin">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_sql_log_bin">
<code class="literal">
sql_log_bin
</code>
</a>
</p>
<a class="indexterm" name="idm46045139307648">
</a>
<a class="indexterm" name="idm46045139306560">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for sql_log_bin">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_sql_log_bin">
sql_log_bin
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Session
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Boolean
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
ON
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
This variable controls whether logging to the binary log is
enabled for the current session (assuming that the binary
log itself is enabled). The default value is
<code class="literal">
ON
</code>
. To disable or enable binary logging
for the current session, set the session
<a class="link" href="replication-options-binary-log.html#sysvar_sql_log_bin">
<code class="literal">
sql_log_bin
</code>
</a>
variable to
<code class="literal">
OFF
</code>
or
<code class="literal">
ON
</code>
.
</p>
<p>
Set this variable to
<code class="literal">
OFF
</code>
for a session to
temporarily disable binary logging while making changes to
the source you do not want replicated to the replica.
</p>
<p>
Setting the session value of this system variable is a
restricted operation. The session user must have privileges
sufficient to set restricted session variables. See
<a class="xref" href="system-variable-privileges.html" title="7.1.9.1 System Variable Privileges">
Section 7.1.9.1, “System Variable Privileges”
</a>
.
</p>
<p>
It is not possible to set the session value of
<a class="link" href="replication-options-binary-log.html#sysvar_sql_log_bin">
<code class="literal">
sql_log_bin
</code>
</a>
within a
transaction or subquery.
</p>
<p>
<span class="emphasis">
<em>
Setting this variable to
<code class="literal">
OFF
</code>
prevents GTIDs from being assigned to transactions in the
binary log
</em>
</span>
. If you are using GTIDs for
replication, this means that even when binary logging is
later enabled again, the GTIDs written into the log from
this point do not account for any transactions that occurred
in the meantime, so in effect those transactions are lost.
</p>
</li>
<li class="listitem">
<p>
<a name="sysvar_sync_binlog">
</a>
<a class="link" href="replication-options-binary-log.html#sysvar_sync_binlog">
<code class="literal">
sync_binlog
</code>
</a>
</p>
<a class="indexterm" name="idm46045139274816">
</a>
<a class="indexterm" name="idm46045139273728">
</a>
<div class="informaltable">
<table frame="box" rules="all" summary="Properties for sync_binlog">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<tbody>
<tr>
<th>
Command-Line Format
</th>
<td>
<code class="literal">
--sync-binlog=#
</code>
</td>
</tr>
<tr>
<th>
System Variable
</th>
<td>
<code class="literal">
<a class="link" href="replication-options-binary-log.html#sysvar_sync_binlog">
sync_binlog
</a>
</code>
</td>
</tr>
<tr>
<th>
Scope
</th>
<td>
Global
</td>
</tr>
<tr>
<th>
Dynamic
</th>
<td>
Yes
</td>
</tr>
<tr>
<th>
<a class="link" href="optimizer-hints.html#optimizer-hints-set-var" title="Variable-Setting Hint Syntax">
<code class="literal">
SET_VAR
</code>
</a>
Hint Applies
</th>
<td>
No
</td>
</tr>
<tr>
<th>
Type
</th>
<td>
Integer
</td>
</tr>
<tr>
<th>
Default Value
</th>
<td>
<code class="literal">
1
</code>
</td>
</tr>
<tr>
<th>
Minimum Value
</th>
<td>
<code class="literal">
0
</code>
</td>
</tr>
<tr>
<th>
Maximum Value
</th>
<td>
<code class="literal">
4294967295
</code>
</td>
</tr>
</tbody>
</table>
</div>
<p>
Controls how often the MySQL server synchronizes the binary
log to disk.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="replication-options-binary-log.html#sysvar_sync_binlog">
<code class="literal">
sync_binlog=0
</code>
</a>
: Disables
synchronization of the binary log to disk by the MySQL
server. Instead, the MySQL server relies on the
operating system to flush the binary log to disk from
time to time as it does for any other file. This setting
provides the best performance, but in the event of a
power failure or operating system crash, it is possible
that the server has committed transactions that have not
been synchronized to the binary log.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replication-options-binary-log.html#sysvar_sync_binlog">
<code class="literal">
sync_binlog=1
</code>
</a>
: Enables
synchronization of the binary log to disk before
transactions are committed. This is the safest setting
but can have a negative impact on performance due to the
increased number of disk writes. In the event of a power
failure or operating system crash, transactions that are
missing from the binary log are only in a prepared
state. This permits the automatic recovery routine to
roll back the transactions, which guarantees that no
transaction is lost from the binary log.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="replication-options-binary-log.html#sysvar_sync_binlog">
<code class="literal">
sync_binlog=
<em class="replaceable">
<code>
N
</code>
</em>
</code>
</a>
,
where
<em class="replaceable">
<code>
N
</code>
</em>
is a value other than
0 or 1: The binary log is synchronized to disk after
<code class="literal">
N
</code>
binary log commit groups have been
collected. In the event of a power failure or operating
system crash, it is possible that the server has
committed transactions that have not been flushed to the
binary log. This setting can have a negative impact on
performance due to the increased number of disk writes.
A higher value improves performance, but with an
increased risk of data loss.
</p>
</li>
</ul>
</div>
<p>
For the greatest possible durability and consistency in a
replication setup that uses
<code class="literal">
InnoDB
</code>
with
transactions, use these settings:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<a class="link" href="replication-options-binary-log.html#sysvar_sync_binlog">
<code class="literal">
sync_binlog=1
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="innodb-parameters.html#sysvar_innodb_flush_log_at_trx_commit">
<code class="literal">
innodb_flush_log_at_trx_commit=1
</code>
</a>
.
</p>
</li>
</ul>
</div>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Caution
</div>
<p>
Many operating systems and some disk hardware fool the
flush-to-disk operation. They may tell
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
that the flush has taken place,
even though it has not. In this case, the durability of
transactions is not guaranteed even with the recommended
settings, and in the worst case, a power outage can
corrupt
<code class="literal">
InnoDB
</code>
data. Using a
battery-backed disk cache in the SCSI disk controller or
in the disk itself speeds up file flushes, and makes the
operation safer. You can also try to disable the caching
of disk writes in hardware caches.
</p>
</div>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-replication-schema.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysql-cluster-replication-schema">
</a>
25.7.4 NDB Cluster Replication Schema and Tables
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045086535216">
</a>
<a class="indexterm" name="idm46045086533728">
</a>
<a class="indexterm" name="idm46045086532272">
</a>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-ndb-apply-status" title="ndb_apply_status Table">
ndb_apply_status Table
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-ndb-binlog-index" title="ndb_binlog_index Table">
ndb_binlog_index Table
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-ndb-replication" title="ndb_replication Table">
ndb_replication Table
</a>
</p>
</li>
</ul>
</div>
<p>
Replication in NDB Cluster makes use of a number of dedicated
tables in the
<code class="literal">
mysql
</code>
database on each MySQL
Server instance acting as an SQL node in both the cluster being
replicated and in the replica. This is true regardless of whether
the replica is a single server or a cluster.
</p>
<p>
The
<code class="literal">
ndb_binlog_index
</code>
and
<code class="literal">
ndb_apply_status
</code>
tables are created in the
<code class="literal">
mysql
</code>
database. They should not be explicitly
replicated by the user. User intervention is normally not required
to create or maintain either of these tables, since both are
maintained by the
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
binary log
(binlog) injector thread. This keeps the source
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
process updated to changes performed by
the
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
storage engine. The
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
<span class="firstterm">
binlog
injector thread
</span>
receives events directly from the
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
storage engine. The
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
injector is responsible for
capturing all the data events within the cluster, and ensures that
all events which change, insert, or delete data are recorded in
the
<code class="literal">
ndb_binlog_index
</code>
table. The replica I/O
(receiver) thread transfers the events from the source's
binary log to the replica's relay log.
</p>
<p>
The
<code class="literal">
ndb_replication
</code>
table must be created
manually. This table can be updated by the user to perform
filtering by database or table. See
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-ndb-replication" title="ndb_replication Table">
ndb_replication Table
</a>
, for more
information.
<code class="literal">
ndb_replication
</code>
is also used in
NDB Replication conflict detection and resolution for conflict
resolution control; see
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-resolution-control" title="Conflict Resolution Control">
Conflict Resolution Control
</a>
.
</p>
<p>
Even though
<code class="literal">
ndb_binlog_index
</code>
and
<code class="literal">
ndb_apply_status
</code>
are created and maintained
automatically, it is advisable to check for the existence and
integrity of these tables as an initial step in preparing an NDB
Cluster for replication. It is possible to view event data
recorded in the binary log by querying the
<code class="literal">
mysql.ndb_binlog_index
</code>
table directly on the
source. This can be also be accomplished using the
<a class="link" href="show-binlog-events.html" title="15.7.7.3 SHOW BINLOG EVENTS Statement">
<code class="literal">
SHOW BINLOG EVENTS
</code>
</a>
statement on
either the source or replica SQL node. (See
<a class="xref" href="show-binlog-events.html" title="15.7.7.3 SHOW BINLOG EVENTS Statement">
Section 15.7.7.3, “SHOW BINLOG EVENTS Statement”
</a>
.)
</p>
<p>
You can also obtain useful information from the output of
<a class="link" href="show-engine.html" title="15.7.7.16 SHOW ENGINE Statement">
<code class="literal">
SHOW ENGINE NDB
STATUS
</code>
</a>
.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
When performing schema changes on
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
tables, applications should
wait until the
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
statement has returned in the MySQL client connection that
issued the statement before attempting to use the updated
definition of the table.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="ndb-replication-ndb-apply-status">
</a>
ndb_apply_status Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045086499456">
</a>
<a class="indexterm" name="idm46045086497936">
</a>
<p>
<code class="literal">
ndb_apply_status
</code>
is used to keep a record of
the operations that have been replicated from the source to the
replica. If the
<code class="literal">
ndb_apply_status
</code>
table does
not exist on the replica,
<a class="link" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup">
<span class="command">
<strong>
ndb_restore
</strong>
</span>
</a>
re-creates it.
</p>
<p>
Unlike the case with
<code class="literal">
ndb_binlog_index
</code>
, the
data in this table is not specific to any one SQL node in the
(replica) cluster, and so
<code class="literal">
ndb_apply_status
</code>
can use the
<code class="literal">
NDBCLUSTER
</code>
storage engine, as
shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa48819377"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>ndb_apply_status<span class="token punctuation">`</span> <span class="token punctuation">(</span>
<span class="token punctuation">`</span>server_id<span class="token punctuation">`</span> <span class="token datatype">INT</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>epoch<span class="token punctuation">`</span> <span class="token datatype">BIGINT</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>log_name<span class="token punctuation">`</span> <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">255</span><span class="token punctuation">)</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> latin1 <span class="token keyword">COLLATE</span> latin1_bin <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>start_pos<span class="token punctuation">`</span> <span class="token datatype">BIGINT</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>end_pos<span class="token punctuation">`</span> <span class="token datatype">BIGINT</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span><span class="token punctuation">`</span>server_id<span class="token punctuation">`</span><span class="token punctuation">)</span> <span class="token keyword">USING</span> <span class="token keyword">HASH</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDBCLUSTER</span> <span class="token keyword">DEFAULT</span> <span class="token keyword">CHARSET</span><span class="token operator">=</span>utf8mb4 <span class="token keyword">COLLATE</span><span class="token operator">=</span>utf8mb4_0900_ai_ci<span class="token punctuation">;</span></code></pre>
</div>
<p>
The
<code class="literal">
ndb_apply_status
</code>
table is populated only
on replicas, which means that, on the source, this table never
contains any rows; thus, there is no need to allot any
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-datamemory">
<code class="literal">
DataMemory
</code>
</a>
to
<code class="literal">
ndb_apply_status
</code>
there.
</p>
<p>
Because this table is populated from data originating on the
source, it should be allowed to replicate; any replication
filtering or binary log filtering rules that inadvertently
prevent the replica from updating
<code class="literal">
ndb_apply_status
</code>
, or that prevent the source
from writing into the binary log may prevent replication between
clusters from operating properly. For more information about
potential problems arising from such filtering rules, see
<a class="xref" href="mysql-cluster-replication-issues.html#mysql-cluster-replication-issues-filtering" title="Replication and binary log filtering rules with replication between NDB Clusters">
Replication and binary log filtering rules with replication between NDB
Clusters
</a>
.
</p>
<p>
It is possible to delete this table, but this is not
recommended. Deleting it puts all SQL nodes in read-only mode;
<code class="literal">
NDB
</code>
detects that this table has been dropped,
and re-creates it, after which it is possible once again to
perform updates. Dropping and re-creating
<code class="literal">
ndb_apply_status
</code>
creates a gap event in the
binary log; the gap event causes replica SQL nodes to stop
applying changes from the source until the replication channel
is restarted.
</p>
<p>
<code class="literal">
0
</code>
in the
<code class="literal">
epoch
</code>
column of
this table indicates a transaction originating from a storage
engine other than
<code class="literal">
NDB
</code>
.
</p>
<p>
<code class="literal">
ndb_apply_status
</code>
is used to record which
epoch transactions have been replicated and applied to a replica
cluster from an upstream source. This information is captured in
an
<code class="literal">
NDB
</code>
online backup, but (by design) it is
not restored by
<a class="link" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup">
<span class="command">
<strong>
ndb_restore
</strong>
</span>
</a>
. In some cases,
it can be helpful to restore this information for use in new
setups; you can do this by invoking
<a class="link" href="mysql-cluster-programs-ndb-restore.html" title="25.5.23 ndb_restore — Restore an NDB Cluster Backup">
<span class="command">
<strong>
ndb_restore
</strong>
</span>
</a>
with the
<a class="link" href="mysql-cluster-programs-ndb-restore.html#option_ndb_restore_with-apply-status">
<code class="option">
--with-apply-status
</code>
</a>
option.
See the description of the option for more information.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="ndb-replication-ndb-binlog-index">
</a>
ndb_binlog_index Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045086471760">
</a>
<a class="indexterm" name="idm46045086470304">
</a>
<p>
NDB Cluster Replication uses the
<code class="literal">
ndb_binlog_index
</code>
table for storing the binary
log's indexing data. Since this table is local to each
MySQL server and does not participate in clustering, it uses the
<a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
<code class="literal">
InnoDB
</code>
</a>
storage engine. This means
that it must be created separately on each
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
participating in the source cluster.
(The binary log itself contains updates from all MySQL servers
in the cluster.) This table is defined as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60048383"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>ndb_binlog_index<span class="token punctuation">`</span> <span class="token punctuation">(</span>
<span class="token punctuation">`</span>Position<span class="token punctuation">`</span> <span class="token datatype">BIGINT</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span><span class="token keyword">File</span><span class="token punctuation">`</span> <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">255</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>epoch<span class="token punctuation">`</span> <span class="token datatype">BIGINT</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>inserts<span class="token punctuation">`</span> <span class="token datatype">INT</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>updates<span class="token punctuation">`</span> <span class="token datatype">INT</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>deletes<span class="token punctuation">`</span> <span class="token datatype">INT</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>schemaops<span class="token punctuation">`</span> <span class="token datatype">INT</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>orig_server_id<span class="token punctuation">`</span> <span class="token datatype">INT</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>orig_epoch<span class="token punctuation">`</span> <span class="token datatype">BIGINT</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>gci<span class="token punctuation">`</span> <span class="token datatype">INT</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">UNSIGNED</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>next_position<span class="token punctuation">`</span> <span class="token datatype">bigint</span><span class="token punctuation">(</span><span class="token number">20</span><span class="token punctuation">)</span> <span class="token keyword">unsigned</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>next_file<span class="token punctuation">`</span> <span class="token datatype">varchar</span><span class="token punctuation">(</span><span class="token number">255</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span><span class="token punctuation">`</span>epoch<span class="token punctuation">`</span><span class="token punctuation">,</span><span class="token punctuation">`</span>orig_server_id<span class="token punctuation">`</span><span class="token punctuation">,</span><span class="token punctuation">`</span>orig_epoch<span class="token punctuation">`</span><span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span>InnoDB <span class="token keyword">DEFAULT</span> <span class="token keyword">CHARSET</span><span class="token operator">=</span>utf8mb4 <span class="token keyword">COLLATE</span><span class="token operator">=</span>utf8mb4_0900_ai_ci<span class="token punctuation">;</span></code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If you are upgrading from an older release, perform the MySQL
upgrade procedure and ensure that the system tables are
upgraded by starting the MySQL server with the
<code class="option">
--upgrade=FORCE
</code>
option. The system table
upgrade causes an
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE ...
ENGINE=INNODB
</code>
</a>
statement to be executed for this
table. Use of the
<code class="literal">
MyISAM
</code>
storage engine for
this table continues to be supported for backward
compatibility.
</p>
<p>
<code class="literal">
ndb_binlog_index
</code>
may require additional
disk space after being converted to
<code class="literal">
InnoDB
</code>
.
If this becomes an issue, you may be able to conserve space by
using an
<code class="literal">
InnoDB
</code>
tablespace for this table,
changing its
<code class="literal">
ROW_FORMAT
</code>
to
<code class="literal">
COMPRESSED
</code>
, or both. For more information,
see
<a class="xref" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
Section 15.1.21, “CREATE TABLESPACE Statement”
</a>
, and
<a class="xref" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
Section 15.1.20, “CREATE TABLE Statement”
</a>
, as well as
<a class="xref" href="innodb-tablespace.html" title="17.6.3 Tablespaces">
Section 17.6.3, “Tablespaces”
</a>
.
</p>
</div>
<p>
The size of the
<code class="literal">
ndb_binlog_index
</code>
table is
dependent on the number of epochs per binary log file and the
number of binary log files. The number of epochs per binary log
file normally depends on the amount of binary log generated per
epoch and the size of the binary log file, with smaller epochs
resulting in more epochs per file. You should be aware that
empty epochs produce inserts to the
<code class="filename">
ndb_binlog_index
</code>
table, even when the
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-empty-epochs">
<code class="option">
--ndb-log-empty-epochs
</code>
</a>
option is
<code class="literal">
OFF
</code>
, meaning that the number of entries per
file depends on the length of time that the file is in use; this
relationship can be represented by the formula shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa90452862"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple"><span class="token punctuation">[</span>number of epochs per file<span class="token punctuation">]</span> <span class="token operator">=</span> <span class="token punctuation">[</span>time spent per file<span class="token punctuation">]</span> <span class="token operator">/</span> TimeBetweenEpochs</code></pre>
</div>
<p>
A busy NDB Cluster writes to the binary log regularly and
presumably rotates binary log files more quickly than a quiet
one. This means that a
<span class="quote">
“
<span class="quote">
quiet
</span>
”
</span>
NDB Cluster with
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-empty-epochs">
<code class="option">
--ndb-log-empty-epochs=ON
</code>
</a>
can
actually have a much higher number of
<code class="literal">
ndb_binlog_index
</code>
rows per file than one with
a great deal of activity.
</p>
<p>
When
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
is started with the
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-orig">
<code class="option">
--ndb-log-orig
</code>
</a>
option, the
<code class="literal">
orig_server_id
</code>
and
<code class="literal">
orig_epoch
</code>
columns store, respectively, the
ID of the server on which the event originated and the epoch in
which the event took place on the originating server, which is
useful in NDB Cluster replication setups employing multiple
sources. The
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statement
used to find the closest binary log position to the highest
applied epoch on the replica in a multi-source setup (see
<a class="xref" href="mysql-cluster-replication-multi-source.html" title="25.7.10 NDB Cluster Replication: Bidirectional and Circular Replication">
Section 25.7.10, “NDB Cluster Replication: Bidirectional and Circular Replication”
</a>
)
employs these two columns, which are not indexed. This can lead
to performance issues when trying to fail over, since the query
must perform a table scan, especially when the source has been
running with
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-empty-epochs">
<code class="option">
--ndb-log-empty-epochs=ON
</code>
</a>
. You
can improve multi-source failover times by adding an index to
these columns, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa53337061"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> mysql<span class="token punctuation">.</span>ndb_binlog_index
<span class="token keyword">ADD</span> <span class="token keyword">INDEX</span> orig_lookup <span class="token keyword">USING</span> <span class="token keyword">BTREE</span> <span class="token punctuation">(</span>orig_server_id<span class="token punctuation">,</span> orig_epoch<span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Adding this index provides no benefit when replicating from a
single source to a single replica, since the query used to get
the binary log position in such cases makes no use of
<code class="literal">
orig_server_id
</code>
or
<code class="literal">
orig_epoch
</code>
.
</p>
<p>
See
<a class="xref" href="mysql-cluster-replication-failover.html" title="25.7.8 Implementing Failover with NDB Cluster Replication">
Section 25.7.8, “Implementing Failover with NDB Cluster Replication”
</a>
, for
more information about using the
<code class="literal">
next_position
</code>
and
<code class="literal">
next_file
</code>
columns.
</p>
<p>
The following figure shows the relationship of the NDB Cluster
replication source server, its binary log injector thread, and
the
<code class="literal">
mysql.ndb_binlog_index
</code>
table.
</p>
<div class="figure">
<a name="fig-mysql-cluster-replication-source-cluster">
</a>
<p class="title">
<b>
Figure 25.13 The Replication Source Cluster
</b>
</p>
<div class="figure-contents">
<div class="mediaobject">
<img alt="Most concepts are described in the surrounding text. This complex image has three main areas. The top left area is divided into three sections: MySQL Server (mysqld), NDBCLUSTER table handler, and mutex. A connection thread connects these, and receiver and injector threads connect the NDBCLUSTER table handler and mutex. The bottom area shows four data nodes (ndbd). They all produce events represented by arrows pointing to the receiver thread, and the receiver thread also points to the connection and injector threads. One node sends and receives to the mutex area. The arrow representing the injector thread points to a binary log as well as the ndb_binlog_index table, which is described in the surrounding text." src="images/cluster-replication-binlog-injector.png" style="width: 100%; max-width: 750px;"/>
</div>
</div>
</div>
<br class="figure-break"/>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="ndb-replication-ndb-replication">
</a>
ndb_replication Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045086420608">
</a>
<a class="indexterm" name="idm46045086419536">
</a>
<p>
The
<code class="literal">
ndb_replication
</code>
table is used to control
binary logging and conflict resolution, and acts on a per-table
basis. Each row in this table corresponds to a table being
replicated, determines how to log changes to the table and, if a
conflict resolution function is specified, and determines how to
resolve conflicts for that table.
</p>
<p>
Unlike the
<code class="literal">
ndb_apply_status
</code>
and
<code class="literal">
ndb_replication
</code>
tables, the
<code class="literal">
ndb_replication
</code>
table must be created
manually, using the SQL statement shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa83724997"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> mysql<span class="token punctuation">.</span>ndb_replication <span class="token punctuation">(</span>
db <span class="token datatype">VARBINARY</span><span class="token punctuation">(</span><span class="token number">63</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">table_name</span> <span class="token datatype">VARBINARY</span><span class="token punctuation">(</span><span class="token number">63</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
server_id <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
binlog_type <span class="token datatype">INT</span> <span class="token keyword">UNSIGNED</span><span class="token punctuation">,</span>
conflict_fn <span class="token datatype">VARBINARY</span><span class="token punctuation">(</span><span class="token number">128</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> <span class="token keyword">USING</span> <span class="token keyword">HASH</span> <span class="token punctuation">(</span>db<span class="token punctuation">,</span> <span class="token keyword">table_name</span><span class="token punctuation">,</span> server_id<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token keyword">NDB</span>
<span class="token keyword">PARTITION</span> <span class="token keyword">BY</span> <span class="token keyword">KEY</span><span class="token punctuation">(</span>db<span class="token punctuation">,</span><span class="token keyword">table_name</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The columns of this table are listed here, with descriptions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
db
</code>
column
</p>
<p>
The name of the database containing the table to be
replicated.
</p>
<p>
You may employ either or both of the wildcards
<code class="literal">
_
</code>
and
<code class="literal">
%
</code>
as part of the
database name. (See
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-wildcards" title="Matching with wildcards">
Matching with wildcards
</a>
, later in this
section.)
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
table_name
</code>
column
</p>
<p>
The name of the table to be replicated.
</p>
<p>
The table name may include either or both of the wildcards
<code class="literal">
_
</code>
and
<code class="literal">
%
</code>
. See
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-wildcards" title="Matching with wildcards">
Matching with wildcards
</a>
, later in this
section.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
server_id
</code>
column
</p>
<p>
The unique server ID of the MySQL instance (SQL node) where
the table resides.
</p>
<p>
<code class="literal">
0
</code>
in this column acts like a wildcard
equivalent to
<code class="literal">
%
</code>
, and matches any server
ID. (See
<a class="xref" href="mysql-cluster-replication-schema.html#ndb-replication-wildcards" title="Matching with wildcards">
Matching with wildcards
</a>
, later
in this section.)
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
binlog_type
</code>
column
</p>
<p>
The type of binary logging to be employed. See text for
values and descriptions.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
conflict_fn
</code>
column
</p>
<p>
The conflict resolution function to be applied; one of
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-old" title="NDB$OLD()">
NDB$OLD()
</a>
,
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-max" title="NDB$MAX()">
NDB$MAX()
</a>
,
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-max-delete-win" title="NDB$MAX_DELETE_WIN()">
NDB$MAX_DELETE_WIN()
</a>
,
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-epoch" title="NDB$EPOCH()">
NDB$EPOCH()
</a>
,
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-epoch-trans" title="NDB$EPOCH_TRANS()">
NDB$EPOCH_TRANS()
</a>
,
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-epoch2" title="NDB$EPOCH2()">
NDB$EPOCH2()
</a>
,
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-epoch2-trans" title="NDB$EPOCH2_TRANS()">
NDB$EPOCH2_TRANS()
</a>
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-max-ins" title="NDB$MAX_INS()">
NDB$MAX_INS()
</a>
, or
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#mysql-cluster-replication-ndb-max-del-win-ins" title="NDB$MAX_DEL_WIN_INS()">
NDB$MAX_DEL_WIN_INS()
</a>
;
<code class="literal">
NULL
</code>
indicates that conflict resolution
is not used for this table.
</p>
<p>
See
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-resolution-functions" title="Conflict Resolution Functions">
Conflict Resolution Functions
</a>
, for
more information about these functions and their uses in NDB
Replication conflict resolution.
</p>
<p>
Some conflict resolution functions
(
<code class="literal">
NDB$OLD()
</code>
,
<code class="literal">
NDB$EPOCH()
</code>
,
<code class="literal">
NDB$EPOCH_TRANS()
</code>
) require the use of one
or more user-created exceptions tables. See
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html#conflict-resolution-exceptions-table" title="Conflict Resolution Exceptions Table">
Conflict Resolution Exceptions Table
</a>
.
</p>
</li>
</ul>
</div>
<p>
To enable conflict resolution with NDB Replication, it is
necessary to create and populate this table with control
information on the SQL node or nodes on which the conflict
should be resolved. Depending on the conflict resolution type
and method to be employed, this may be the source, the replica,
or both servers. In a simple source-replica setup where data can
also be changed locally on the replica this is typically the
replica. In a more complex replication scheme, such as
bidirectional replication, this is usually all of the sources
involved. See
<a class="xref" href="mysql-cluster-replication-conflict-resolution.html" title="25.7.12 NDB Cluster Replication Conflict Resolution">
Section 25.7.12, “NDB Cluster Replication Conflict Resolution”
</a>
,
for more information.
</p>
<p>
The
<code class="literal">
ndb_replication
</code>
table allows table-level
control over binary logging outside the scope of conflict
resolution, in which case
<code class="literal">
conflict_fn
</code>
is
specified as
<code class="literal">
NULL
</code>
, while the remaining column
values are used to control binary logging for a given table or
set of tables matching a wildcard expression. By setting the
proper value for the
<code class="literal">
binlog_type
</code>
column, you
can make logging for a given table or tables use a desired
binary log format, or disabling binary logging altogether.
Possible values for this column, with
values and descriptions, are shown in the following table:
</p>
<div class="table">
<a name="idm46045086374816">
</a>
<p class="title">
<b>
Table 25.42 binlog_type values, with values and descriptions
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col width="10%"/>
<col width="55%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Value
</th>
<th scope="col">
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
0
</th>
<td>
Use server default
</td>
</tr>
<tr>
<th scope="row">
1
</th>
<td>
Do not log this table in the binary log (same effect as
<a class="link" href="replication-options-binary-log.html#sysvar_sql_log_bin">
<code class="literal">
sql_log_bin = 0
</code>
</a>
, but
applies to one or more specified tables only)
</td>
</tr>
<tr>
<th scope="row">
2
</th>
<td>
Log updated attributes only; log these as
<code class="literal">
WRITE_ROW
</code>
events
</td>
</tr>
<tr>
<th scope="row">
3
</th>
<td>
Log full row, even if not updated (MySQL server default behavior)
</td>
</tr>
<tr>
<th scope="row">
6
</th>
<td>
Use updated attributes, even if values are unchanged
</td>
</tr>
<tr>
<th scope="row">
7
</th>
<td>
Log full row, even if no values are changed; log updates as
<code class="literal">
UPDATE_ROW
</code>
events
</td>
</tr>
<tr>
<th scope="row">
8
</th>
<td>
Log update as
<code class="literal">
UPDATE_ROW
</code>
; log only primary key
columns in before image, and only updated columns in after
image (same effect as
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-minimal">
<code class="option">
--ndb-log-update-minimal
</code>
</a>
,
but applies to one or more specified tables only)
</td>
</tr>
<tr>
<th scope="row">
9
</th>
<td>
Log update as
<code class="literal">
UPDATE_ROW
</code>
; log only primary key
columns in before image, and all columns other than
primary key columns in after image
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
<code class="literal">
binlog_type
</code>
values 4 and 5 are not used,
and so are omitted from the table just shown, as well as from
the next table.
</p>
</div>
<p>
Several
<code class="literal">
binlog_type
</code>
values are equivalent to
various combinations of the
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
logging
options
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-updated-only">
<code class="option">
--ndb-log-updated-only
</code>
</a>
,
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-as-write">
<code class="option">
--ndb-log-update-as-write
</code>
</a>
, and
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-minimal">
<code class="option">
--ndb-log-update-minimal
</code>
</a>
, as
shown in the following table:
</p>
<div class="table">
<a name="idm46045086336368">
</a>
<p class="title">
<b>
Table 25.43 binlog_type values with equivalent combinations of NDB logging options
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col width="10%"/>
<col width="30%"/>
<col width="30%"/>
<col width="30%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
Value
</th>
<th scope="col">
<code class="option">
--ndb-log-updated-only
</code>
Value
</th>
<th scope="col">
<code class="option">
--ndb-log-update-as-write
</code>
Value
</th>
<th scope="col">
<code class="option">
--ndb-log-update-minimal
</code>
Value
</th>
</tr>
</thead>
<tbody>
<tr>
<th scope="row">
0
</th>
<td>
--
</td>
<td>
--
</td>
<td>
--
</td>
</tr>
<tr>
<th scope="row">
1
</th>
<td>
--
</td>
<td>
--
</td>
<td>
--
</td>
</tr>
<tr>
<th scope="row">
2
</th>
<td>
ON
</td>
<td>
ON
</td>
<td>
OFF
</td>
</tr>
<tr>
<th scope="row">
3
</th>
<td>
OFF
</td>
<td>
ON
</td>
<td>
OFF
</td>
</tr>
<tr>
<th scope="row">
6
</th>
<td>
ON
</td>
<td>
OFF
</td>
<td>
OFF
</td>
</tr>
<tr>
<th scope="row">
7
</th>
<td>
OFF
</td>
<td>
OFF
</td>
<td>
OFF
</td>
</tr>
<tr>
<th scope="row">
8
</th>
<td>
ON
</td>
<td>
OFF
</td>
<td>
ON
</td>
</tr>
<tr>
<th scope="row">
9
</th>
<td>
OFF
</td>
<td>
OFF
</td>
<td>
ON
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>
Binary logging can be set to different formats for different
tables by inserting rows into the
<code class="literal">
ndb_replication
</code>
table using the appropriate
<code class="literal">
db
</code>
,
<code class="literal">
table_name
</code>
, and
<code class="literal">
binlog_type
</code>
column values. The internal
integer value shown in the preceding table should be used when
setting the binary logging format. The following two statements
set binary logging to logging of full rows (
value 3) for table
<code class="literal">
test.a
</code>
, and to logging of
updates only (
value 2) for table
<code class="literal">
test.b
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa61641893"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token comment" spellcheck="true"># Table test.a: Log full rows</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> mysql<span class="token punctuation">.</span>ndb_replication <span class="token keyword">VALUES</span><span class="token punctuation">(</span><span class="token string">"test"</span><span class="token punctuation">,</span> <span class="token string">"a"</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token boolean">NULL</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment" spellcheck="true"># Table test.b: log updates only</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> mysql<span class="token punctuation">.</span>ndb_replication <span class="token keyword">VALUES</span><span class="token punctuation">(</span><span class="token string">"test"</span><span class="token punctuation">,</span> <span class="token string">"b"</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token boolean">NULL</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To disable logging for one or more tables, use 1
for
<code class="literal">
binlog_type
</code>
, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa64870822"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token comment" spellcheck="true"># Disable binary logging for table test.t1</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> mysql<span class="token punctuation">.</span>ndb_replication <span class="token keyword">VALUES</span><span class="token punctuation">(</span><span class="token string">"test"</span><span class="token punctuation">,</span> <span class="token string">"t1"</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token boolean">NULL</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment" spellcheck="true"># Disable binary logging for any table in 'test' whose name begins with 't'</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> mysql<span class="token punctuation">.</span>ndb_replication <span class="token keyword">VALUES</span><span class="token punctuation">(</span><span class="token string">"test"</span><span class="token punctuation">,</span> <span class="token string">"t%"</span><span class="token punctuation">,</span> <span class="token number">0</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token boolean">NULL</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Disabling logging
for a given table is the equivalent of setting
<a class="link" href="replication-options-binary-log.html#sysvar_sql_log_bin">
<code class="literal">
sql_log_bin = 0
</code>
</a>
, except that it
applies to one or more tables individually.
If an SQL node is not performing binary logging for a given
table, it is not sent the row change events for those tables.
This means that it is not receiving all changes and discarding
some, but rather it is not subscribing to these changes.
</p>
<p>
Disabling logging
can be useful for a number of reasons, including those listed
here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Not sending changes across the network generally saves
bandwidth, buffering, and CPU resources.
</p>
</li>
<li class="listitem">
<p>
Not logging changes to tables with very frequent updates but
whose value is not great is a good fit for transient data
(such as session data) that may be relatively unimportant in
the event of a complete failure of the cluster.
</p>
</li>
<li class="listitem">
<p>
Using a session variable (or
<code class="literal">
sql_log_bin
</code>
)
and application code, it is also possible to log (or not to
log) certain SQL statements or types of SQL statements; for
example, it may be desirable in some cases not to record DDL
statements on one or more tables.
</p>
</li>
<li class="listitem">
<p>
Splitting replication streams into two (or more) binary logs
can be done for reasons of performance, a need to replicate
different databases to different places, use of different
binary logging types for different databases, and so on.
</p>
</li>
</ul>
</div>
<p>
<a name="ndb-replication-wildcards">
</a>
<b>
Matching with wildcards.
</b>
In order not to make it necessary to insert a row in the
<code class="literal">
ndb_replication
</code>
table for each and every
combination of database, table, and SQL node in your
replication setup,
<code class="literal">
NDB
</code>
supports wildcard
matching on the this table's
<code class="literal">
db
</code>
,
<code class="literal">
table_name
</code>
, and
<code class="literal">
server_id
</code>
columns. Database and table names
used in, respectively,
<code class="literal">
db
</code>
and
<code class="literal">
table_name
</code>
may contain either or both of
the following wildcards:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
_
</code>
(underscore character): matches zero or
more characters
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
%
</code>
(percent sign): matches a single
character
</p>
</li>
</ul>
</div>
<p>
(These are the same wildcards as supported by the MySQL
<a class="link" href="string-comparison-functions.html#operator_like">
<code class="literal">
LIKE
</code>
</a>
operator.)
</p>
<p>
The
<code class="literal">
server_id
</code>
column supports
<code class="literal">
0
</code>
as a wildcard equivalent to
<code class="literal">
_
</code>
(matches anything). This is used in the
examples shown previously.
</p>
<p>
A given row in the
<code class="literal">
ndb_replication
</code>
table can
use wildcards to match any of the database name, table name, and
server ID in any combination. Where there are multiple potential
matches in the table, the best match is chosen, according to the
table shown here, where
<span class="emphasis">
<em>
W
</em>
</span>
represents a
wildcard match,
<span class="emphasis">
<em>
E
</em>
</span>
an exact match, and the
greater the value in the
<span class="emphasis">
<em>
Quality
</em>
</span>
column,
the better the match:
</p>
<div class="table">
<a name="idm46045086258784">
</a>
<p class="title">
<b>
Table 25.44
Weights of different combinations of wildcard and
exact matches on columns in the mysql.ndb_replication
table
</b>
</p>
<div class="table-contents">
<table>
<colgroup>
<col style="width: 25%"/>
<col style="width: 25%"/>
<col style="width: 25%"/>
<col style="width: 25%"/>
</colgroup>
<thead>
<tr>
<th scope="col">
<code class="literal">
db
</code>
</th>
<th scope="col">
<code class="literal">
table_name
</code>
</th>
<th scope="col">
<code class="literal">
server_id
</code>
</th>
<th scope="col">
Quality
</th>
</tr>
</thead>
<tbody>
<tr>
<td scope="row">
W
</td>
<td>
W
</td>
<td>
W
</td>
<td>
1
</td>
</tr>
<tr>
<td scope="row">
W
</td>
<td>
W
</td>
<td>
E
</td>
<td>
2
</td>
</tr>
<tr>
<td scope="row">
W
</td>
<td>
E
</td>
<td>
W
</td>
<td>
3
</td>
</tr>
<tr>
<td scope="row">
W
</td>
<td>
E
</td>
<td>
E
</td>
<td>
4
</td>
</tr>
<tr>
<td scope="row">
E
</td>
<td>
W
</td>
<td>
W
</td>
<td>
5
</td>
</tr>
<tr>
<td scope="row">
E
</td>
<td>
W
</td>
<td>
E
</td>
<td>
6
</td>
</tr>
<tr>
<td scope="row">
E
</td>
<td>
E
</td>
<td>
W
</td>
<td>
7
</td>
</tr>
<tr>
<td scope="row">
E
</td>
<td>
E
</td>
<td>
E
</td>
<td>
8
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>
Thus, an exact match on database name, table name, and server ID
is considered best (strongest), while the weakest (worst) match
is a wildcard match on all three columns. Only the strength of
the match is considered when choosing which rule to apply; the
order in which the rows occur in the table has no effect on this
determination.
</p>
<p>
<a name="ndb-replication-full-or-partial">
</a>
<b>
Logging Full or Partial Rows.
</b>
<a class="indexterm" name="idm46045086213104">
</a>
There are two basic methods of logging rows, as determined by
the setting of the
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-updated-only">
<code class="option">
--ndb-log-updated-only
</code>
</a>
option
for
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Log complete rows (option set to
<code class="literal">
ON
</code>
)
</p>
</li>
<li class="listitem">
<p>
Log only column data that has been updated—that is,
column data whose value has been set, regardless of whether
or not this value was actually changed. This is the default
behavior (option set to
<code class="literal">
OFF
</code>
).
</p>
</li>
</ul>
</div>
<p>
It is usually sufficient—and more efficient—to log
updated columns only; however, if you need to log full rows, you
can do so by setting
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-updated-only">
<code class="option">
--ndb-log-updated-only
</code>
</a>
to
<code class="literal">
0
</code>
or
<code class="literal">
OFF
</code>
.
</p>
<p>
<a name="ndb-replication-changes-as-updates">
</a>
<b>
Logging Changed Data as Updates.
</b>
<a class="indexterm" name="idm46045086201040">
</a>
The setting of the MySQL Server's
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-as-write">
<code class="option">
--ndb-log-update-as-write
</code>
</a>
option determines whether logging is performed with or without
the
<span class="quote">
“
<span class="quote">
before
</span>
”
</span>
image.
</p>
<p>
Because conflict resolution for updates and delete operations is
done in the MySQL Server's update handler, it is necessary
to control the logging performed by the replication source such
that updates are updates and not writes; that is, such that
updates are treated as changes in existing rows rather than the
writing of new rows, even though these replace existing rows.
</p>
<p>
This option is turned on by default; in other words, updates are
treated as writes. That is, updates are by default written as
<code class="literal">
write_row
</code>
events in the binary log, rather
than as
<code class="literal">
update_row
</code>
events.
</p>
<p>
To disable the option, start the source
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
with
<code class="option">
--ndb-log-update-as-write=0
</code>
or
<code class="option">
--ndb-log-update-as-write=OFF
</code>
. You must do this
when replicating from NDB tables to tables using a different
storage engine; see
<a class="xref" href="mysql-cluster-replication-issues.html#mysql-cluster-replication-ndb-to-non-ndb" title="Replication from NDB to other storage engines">
Replication from NDB to other storage engines
</a>
, and
<a class="xref" href="mysql-cluster-replication-issues.html#mysql-cluster-replication-ndb-to-nontransactional" title="Replication from NDB to a nontransactional storage engine">
Replication from NDB to a nontransactional storage engine
</a>
,
for more information.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
For insert conflict resolution using
<code class="literal">
NDB$MAX_INS()
</code>
or
<code class="literal">
NDB$MAX_DEL_WIN_INS()
</code>
, an SQL node (that
is, a
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
process) can record row
updates on the source cluster as
<code class="literal">
WRITE_ROW
</code>
events with the
<a class="link" href="mysql-cluster-options-variables.html#option_mysqld_ndb-log-update-as-write">
<code class="option">
--ndb-log-update-as-write
</code>
</a>
option enabled for idempotency and optimal size. This works
for these algorithms since they both map a
<code class="literal">
WRITE_ROW
</code>
event to an insert or update
depending on whether the row already exists, and the required
metadata (the
<span class="quote">
“
<span class="quote">
after
</span>
”
</span>
image for the timestamp
column) is present in the
<span class="quote">
“
<span class="quote">
WRITE_ROW
</span>
”
</span>
event.
</p>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/regexp.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="regexp">
</a>
14.8.2 Regular Expressions
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045202491536">
</a>
<a class="indexterm" name="idm46045202490464">
</a>
<a class="indexterm" name="idm46045202489392">
</a>
<a class="indexterm" name="idm46045202488304">
</a>
<div class="table">
<a name="idm46045202486816">
</a>
<p class="title">
<b>
Table 14.14 Regular Expression Functions and
Operators
</b>
</p>
<div class="table-contents">
<table frame="box" rules="all" summary="A reference that lists regular expression functions and operators.">
<colgroup>
<col style="width: 28%"/>
<col style="width: 71%"/>
</colgroup>
<thead>
<tr>
<th>
Name
</th>
<th>
Description
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<a class="link" href="regexp.html#operator_not-regexp">
<code class="literal">
NOT REGEXP
</code>
</a>
</td>
<td>
Negation of REGEXP
</td>
</tr>
<tr>
<td>
<a class="link" href="regexp.html#operator_regexp">
<code class="literal">
REGEXP
</code>
</a>
</td>
<td>
Whether string matches regular expression
</td>
</tr>
<tr>
<td>
<a class="link" href="regexp.html#function_regexp-instr">
<code class="literal">
REGEXP_INSTR()
</code>
</a>
</td>
<td>
Starting index of substring matching regular expression
</td>
</tr>
<tr>
<td>
<a class="link" href="regexp.html#function_regexp-like">
<code class="literal">
REGEXP_LIKE()
</code>
</a>
</td>
<td>
Whether string matches regular expression
</td>
</tr>
<tr>
<td>
<a class="link" href="regexp.html#function_regexp-replace">
<code class="literal">
REGEXP_REPLACE()
</code>
</a>
</td>
<td>
Replace substrings matching regular expression
</td>
</tr>
<tr>
<td>
<a class="link" href="regexp.html#function_regexp-substr">
<code class="literal">
REGEXP_SUBSTR()
</code>
</a>
</td>
<td>
Return substring matching regular expression
</td>
</tr>
<tr>
<td>
<a class="link" href="regexp.html#operator_regexp">
<code class="literal">
RLIKE
</code>
</a>
</td>
<td>
Whether string matches regular expression
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>
A regular expression is a powerful way of specifying a pattern
for a complex search. This section discusses the functions and
operators available for regular expression matching and
illustrates, with examples, some of the special characters and
constructs that can be used for regular expression operations.
See also
<a class="xref" href="pattern-matching.html" title="5.3.4.7 Pattern Matching">
Section 5.3.4.7, “Pattern Matching”
</a>
.
</p>
<p>
MySQL implements regular expression support using International
Components for Unicode (ICU), which provides full Unicode
support and is multibyte safe.
</p>
<p>
Use of a binary string with any of the MySQL regular expression
functions is rejected with
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_character_set_mismatch" target="_top">
<code class="literal">
ER_CHARACTER_SET_MISMATCH
</code>
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="regexp.html#regexp-operator-descriptions" title="Regular Expression Function and Operator Descriptions">
Regular Expression Function and Operator Descriptions
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="regexp.html#regexp-syntax" title="Regular Expression Syntax">
Regular Expression Syntax
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="regexp.html#regexp-resource-control" title="Regular Expression Resource Control">
Regular Expression Resource Control
</a>
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="regexp-operator-descriptions">
</a>
Regular Expression Function and Operator Descriptions
</h4>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<a name="operator_not-regexp">
</a>
<p>
<a class="link" href="regexp.html#operator_not-regexp">
<code class="literal">
<em class="replaceable">
<code>
expr
</code>
</em>
NOT REGEXP
<em class="replaceable">
<code>
pat
</code>
</em>
</code>
</a>
,
<a class="link" href="regexp.html#operator_not-regexp">
<code class="literal">
<em class="replaceable">
<code>
expr
</code>
</em>
NOT RLIKE
<em class="replaceable">
<code>
pat
</code>
</em>
</code>
</a>
</p>
<a class="indexterm" name="idm46045202444368">
</a>
<p>
This is the same as
<code class="literal">
NOT
(
<em class="replaceable">
<code>
expr
</code>
</em>
REGEXP
<em class="replaceable">
<code>
pat
</code>
</em>
)
</code>
.
</p>
</li>
<li class="listitem">
<a name="operator_regexp">
</a>
<p>
<a class="link" href="regexp.html#operator_regexp">
<code class="literal">
<em class="replaceable">
<code>
expr
</code>
</em>
REGEXP
<em class="replaceable">
<code>
pat
</code>
</em>
</code>
</a>
,
<a class="link" href="regexp.html#operator_regexp">
<code class="literal">
<em class="replaceable">
<code>
expr
</code>
</em>
RLIKE
<em class="replaceable">
<code>
pat
</code>
</em>
</code>
</a>
</p>
<a class="indexterm" name="idm46045202432976">
</a>
<a class="indexterm" name="idm46045202431904">
</a>
<p>
Returns 1 if the string
<em class="replaceable">
<code>
expr
</code>
</em>
matches the regular expression specified by the pattern
<em class="replaceable">
<code>
pat
</code>
</em>
, 0 otherwise. If
<em class="replaceable">
<code>
expr
</code>
</em>
or
<em class="replaceable">
<code>
pat
</code>
</em>
is
<code class="literal">
NULL
</code>
,
the return value is
<code class="literal">
NULL
</code>
.
</p>
<p>
<a class="link" href="regexp.html#operator_regexp">
<code class="literal">
REGEXP
</code>
</a>
and
<a class="link" href="regexp.html#operator_regexp">
<code class="literal">
RLIKE
</code>
</a>
are
synonyms for
<a class="link" href="regexp.html#function_regexp-like">
<code class="literal">
REGEXP_LIKE()
</code>
</a>
.
</p>
<p>
For additional information about how matching occurs, see
the description for
<a class="link" href="regexp.html#function_regexp-like">
<code class="literal">
REGEXP_LIKE()
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51708473"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token string">'Michael!'</span> <span class="token operator">REGEXP</span> <span class="token string">'.*'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 'Michael!' REGEXP '.*' <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token string">'new*\n*line'</span> <span class="token operator">REGEXP</span> <span class="token string">'new\\*.\\*line'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 'new*\n*line' REGEXP 'new\\*.\\*line' <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token string">'a'</span> <span class="token operator">REGEXP</span> <span class="token string">'^[a-d]'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 'a' REGEXP '^[a<span class="token punctuation">-</span>d]' <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_regexp-instr">
</a>
<p>
<a class="link" href="regexp.html#function_regexp-instr">
<code class="literal">
REGEXP_INSTR(
<em class="replaceable">
<code>
expr
</code>
</em>
,
<em class="replaceable">
<code>
pat
</code>
</em>
[,
<em class="replaceable">
<code>
pos
</code>
</em>
[,
<em class="replaceable">
<code>
occurrence
</code>
</em>
[,
<em class="replaceable">
<code>
return_option
</code>
</em>
[,
<em class="replaceable">
<code>
match_type
</code>
</em>
]]]])
</code>
</a>
</p>
<a class="indexterm" name="idm46045202408144">
</a>
<p>
Returns the starting index of the substring of the string
<em class="replaceable">
<code>
expr
</code>
</em>
that matches the regular
expression specified by the pattern
<em class="replaceable">
<code>
pat
</code>
</em>
, 0 if there is no match. If
<em class="replaceable">
<code>
expr
</code>
</em>
or
<em class="replaceable">
<code>
pat
</code>
</em>
is
<code class="literal">
NULL
</code>
,
the return value is
<code class="literal">
NULL
</code>
. Character
indexes begin at 1.
</p>
<p>
<a class="link" href="regexp.html#function_regexp-instr">
<code class="literal">
REGEXP_INSTR()
</code>
</a>
takes these
optional arguments:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<em class="replaceable">
<code>
pos
</code>
</em>
: The position in
<em class="replaceable">
<code>
expr
</code>
</em>
at which to start the
search. If omitted, the default is 1.
</p>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
occurrence
</code>
</em>
: Which
occurrence of a match to search for. If omitted, the
default is 1.
</p>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
return_option
</code>
</em>
: Which type
of position to return. If this value is 0,
<a class="link" href="regexp.html#function_regexp-instr">
<code class="literal">
REGEXP_INSTR()
</code>
</a>
returns
the position of the matched substring's first
character. If this value is 1,
<a class="link" href="regexp.html#function_regexp-instr">
<code class="literal">
REGEXP_INSTR()
</code>
</a>
returns
the position following the matched substring. If
omitted, the default is 0.
</p>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
match_type
</code>
</em>
: A string that
specifies how to perform matching. The meaning is as
described for
<a class="link" href="regexp.html#function_regexp-like">
<code class="literal">
REGEXP_LIKE()
</code>
</a>
.
</p>
</li>
</ul>
</div>
<p>
For additional information about how matching occurs, see
the description for
<a class="link" href="regexp.html#function_regexp-like">
<code class="literal">
REGEXP_LIKE()
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa46406074"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_INSTR</span><span class="token punctuation">(</span><span class="token string">'dog cat dog'</span><span class="token punctuation">,</span> <span class="token string">'dog'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_INSTR('dog cat dog', 'dog') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_INSTR</span><span class="token punctuation">(</span><span class="token string">'dog cat dog'</span><span class="token punctuation">,</span> <span class="token string">'dog'</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_INSTR('dog cat dog', 'dog', 2) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 9 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_INSTR</span><span class="token punctuation">(</span><span class="token string">'aa aaa aaaa'</span><span class="token punctuation">,</span> <span class="token string">'a{2}'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_INSTR('aa aaa aaaa', 'a{2}') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_INSTR</span><span class="token punctuation">(</span><span class="token string">'aa aaa aaaa'</span><span class="token punctuation">,</span> <span class="token string">'a{4}'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_INSTR('aa aaa aaaa', 'a{4}') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 8 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_regexp-like">
</a>
<p>
<a class="link" href="regexp.html#function_regexp-like">
<code class="literal">
REGEXP_LIKE(
<em class="replaceable">
<code>
expr
</code>
</em>
,
<em class="replaceable">
<code>
pat
</code>
</em>
[,
<em class="replaceable">
<code>
match_type
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045202377232">
</a>
<p>
Returns 1 if the string
<em class="replaceable">
<code>
expr
</code>
</em>
matches the regular expression specified by the pattern
<em class="replaceable">
<code>
pat
</code>
</em>
, 0 otherwise. If
<em class="replaceable">
<code>
expr
</code>
</em>
or
<em class="replaceable">
<code>
pat
</code>
</em>
is
<code class="literal">
NULL
</code>
,
the return value is
<code class="literal">
NULL
</code>
.
</p>
<p>
The pattern can be an extended regular expression, the
syntax for which is discussed in
<a class="xref" href="regexp.html#regexp-syntax" title="Regular Expression Syntax">
Regular Expression Syntax
</a>
. The pattern need not be a
literal string. For example, it can be specified as a
string expression or table column.
</p>
<p>
The optional
<em class="replaceable">
<code>
match_type
</code>
</em>
argument is a string that may contain any or all the
following characters specifying how to perform matching:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
c
</code>
: Case-sensitive matching.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
i
</code>
: Case-insensitive matching.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
m
</code>
: Multiple-line mode. Recognize
line terminators within the string. The default
behavior is to match line terminators only at the
start and end of the string expression.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
n
</code>
: The
<code class="literal">
.
</code>
character matches line terminators. The default is for
<code class="literal">
.
</code>
matching to stop at the end of a
line.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
u
</code>
: Unix-only line endings. Only the
newline character is recognized as a line ending by
the
<code class="literal">
.
</code>
,
<code class="literal">
^
</code>
, and
<code class="literal">
$
</code>
match operators.
</p>
</li>
</ul>
</div>
<p>
If characters specifying contradictory options are
specified within
<em class="replaceable">
<code>
match_type
</code>
</em>
,
the rightmost one takes precedence.
</p>
<p>
By default, regular expression operations use the
character set and collation of the
<em class="replaceable">
<code>
expr
</code>
</em>
and
<em class="replaceable">
<code>
pat
</code>
</em>
arguments when deciding the
type of a character and performing the comparison. If the
arguments have different character sets or collations,
coercibility rules apply as described in
<a class="xref" href="charset-collation-coercibility.html" title="12.8.4 Collation Coercibility in Expressions">
Section 12.8.4, “Collation Coercibility in Expressions”
</a>
.
Arguments may be specified with explicit collation
indicators to change comparison behavior.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa6957101"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'CamelCase'</span><span class="token punctuation">,</span> <span class="token string">'CAMELCASE'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_LIKE('CamelCase', 'CAMELCASE') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'CamelCase'</span><span class="token punctuation">,</span> <span class="token string">'CAMELCASE'</span> <span class="token keyword">COLLATE</span> utf8mb4_0900_as_cs<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_LIKE('CamelCase', 'CAMELCASE' COLLATE utf8mb4_0900_as_cs) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
<em class="replaceable">
<code>
match_type
</code>
</em>
may be specified
with the
<code class="literal">
c
</code>
or
<code class="literal">
i
</code>
characters to override the default case sensitivity.
Exception: If either argument is a binary string, the
arguments are handled in case-sensitive fashion as binary
strings, even if
<em class="replaceable">
<code>
match_type
</code>
</em>
contains the
<code class="literal">
i
</code>
character.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
MySQL uses C escape syntax in strings (for example,
<code class="literal">
\n
</code>
to represent the newline
character). If you want your
<em class="replaceable">
<code>
expr
</code>
</em>
or
<em class="replaceable">
<code>
pat
</code>
</em>
argument to contain a
literal
<code class="literal">
\
</code>
, you must double it.
(Unless the
<a class="link" href="sql-mode.html#sqlmode_no_backslash_escapes">
<code class="literal">
NO_BACKSLASH_ESCAPES
</code>
</a>
SQL mode is enabled, in which case no escape character
is used.)
</p>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99587389"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'Michael!'</span><span class="token punctuation">,</span> <span class="token string">'.*'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_LIKE('Michael!', '.*') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'new*\n*line'</span><span class="token punctuation">,</span> <span class="token string">'new\\*.\\*line'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_LIKE('new*\n*line', 'new\\*.\\*line') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'a'</span><span class="token punctuation">,</span> <span class="token string">'^[a-d]'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_LIKE('a', '^[a<span class="token punctuation">-</span>d]') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa47306581"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'abc'</span><span class="token punctuation">,</span> <span class="token string">'ABC'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_LIKE('abc', 'ABC') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'abc'</span><span class="token punctuation">,</span> <span class="token string">'ABC'</span><span class="token punctuation">,</span> <span class="token string">'c'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_LIKE('abc', 'ABC', 'c') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_regexp-replace">
</a>
<p>
<a class="link" href="regexp.html#function_regexp-replace">
<code class="literal">
REGEXP_REPLACE(
<em class="replaceable">
<code>
expr
</code>
</em>
,
<em class="replaceable">
<code>
pat
</code>
</em>
,
<em class="replaceable">
<code>
repl
</code>
</em>
[,
<em class="replaceable">
<code>
pos
</code>
</em>
[,
<em class="replaceable">
<code>
occurrence
</code>
</em>
[,
<em class="replaceable">
<code>
match_type
</code>
</em>
]]])
</code>
</a>
</p>
<a class="indexterm" name="idm46045202327888">
</a>
<p>
Replaces occurrences in the string
<em class="replaceable">
<code>
expr
</code>
</em>
that match the regular
expression specified by the pattern
<em class="replaceable">
<code>
pat
</code>
</em>
with the replacement string
<em class="replaceable">
<code>
repl
</code>
</em>
, and returns the resulting
string. If
<em class="replaceable">
<code>
expr
</code>
</em>
,
<em class="replaceable">
<code>
pat
</code>
</em>
, or
<em class="replaceable">
<code>
repl
</code>
</em>
is
<code class="literal">
NULL
</code>
, the return value is
<code class="literal">
NULL
</code>
.
</p>
<p>
<a class="link" href="regexp.html#function_regexp-replace">
<code class="literal">
REGEXP_REPLACE()
</code>
</a>
takes
these optional arguments:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<em class="replaceable">
<code>
pos
</code>
</em>
: The position in
<em class="replaceable">
<code>
expr
</code>
</em>
at which to start the
search. If omitted, the default is 1.
</p>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
occurrence
</code>
</em>
: Which
occurrence of a match to replace. If omitted, the
default is 0 (which means
<span class="quote">
“
<span class="quote">
replace all
occurrences
</span>
”
</span>
).
</p>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
match_type
</code>
</em>
: A string that
specifies how to perform matching. The meaning is as
described for
<a class="link" href="regexp.html#function_regexp-like">
<code class="literal">
REGEXP_LIKE()
</code>
</a>
.
</p>
</li>
</ul>
</div>
<p>
The result returned by this function uses the character
set and collation of the expression searched for matches.
</p>
<p>
For additional information about how matching occurs, see
the description for
<a class="link" href="regexp.html#function_regexp-like">
<code class="literal">
REGEXP_LIKE()
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60205605"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_REPLACE</span><span class="token punctuation">(</span><span class="token string">'a b c'</span><span class="token punctuation">,</span> <span class="token string">'b'</span><span class="token punctuation">,</span> <span class="token string">'X'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_REPLACE('a b c', 'b', 'X') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> a X c <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_REPLACE</span><span class="token punctuation">(</span><span class="token string">'abc def ghi'</span><span class="token punctuation">,</span> <span class="token string">'[a-z]+'</span><span class="token punctuation">,</span> <span class="token string">'X'</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_REPLACE('abc def ghi', '[a<span class="token punctuation">-</span>z]<span class="token punctuation">+</span>', 'X', 1, 3) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> abc def X <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_regexp-substr">
</a>
<p>
<a class="link" href="regexp.html#function_regexp-substr">
<code class="literal">
REGEXP_SUBSTR(
<em class="replaceable">
<code>
expr
</code>
</em>
,
<em class="replaceable">
<code>
pat
</code>
</em>
[,
<em class="replaceable">
<code>
pos
</code>
</em>
[,
<em class="replaceable">
<code>
occurrence
</code>
</em>
[,
<em class="replaceable">
<code>
match_type
</code>
</em>
]]])
</code>
</a>
</p>
<a class="indexterm" name="idm46045202300352">
</a>
<p>
Returns the substring of the string
<em class="replaceable">
<code>
expr
</code>
</em>
that matches the regular
expression specified by the pattern
<em class="replaceable">
<code>
pat
</code>
</em>
,
<code class="literal">
NULL
</code>
if
there is no match. If
<em class="replaceable">
<code>
expr
</code>
</em>
or
<em class="replaceable">
<code>
pat
</code>
</em>
is
<code class="literal">
NULL
</code>
,
the return value is
<code class="literal">
NULL
</code>
.
</p>
<p>
<a class="link" href="regexp.html#function_regexp-substr">
<code class="literal">
REGEXP_SUBSTR()
</code>
</a>
takes these
optional arguments:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<em class="replaceable">
<code>
pos
</code>
</em>
: The position in
<em class="replaceable">
<code>
expr
</code>
</em>
at which to start the
search. If omitted, the default is 1.
</p>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
occurrence
</code>
</em>
: Which
occurrence of a match to search for. If omitted, the
default is 1.
</p>
</li>
<li class="listitem">
<p>
<em class="replaceable">
<code>
match_type
</code>
</em>
: A string that
specifies how to perform matching. The meaning is as
described for
<a class="link" href="regexp.html#function_regexp-like">
<code class="literal">
REGEXP_LIKE()
</code>
</a>
.
</p>
</li>
</ul>
</div>
<p>
The result returned by this function uses the character
set and collation of the expression searched for matches.
</p>
<p>
For additional information about how matching occurs, see
the description for
<a class="link" href="regexp.html#function_regexp-like">
<code class="literal">
REGEXP_LIKE()
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa40903981"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_SUBSTR</span><span class="token punctuation">(</span><span class="token string">'abc def ghi'</span><span class="token punctuation">,</span> <span class="token string">'[a-z]+'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_SUBSTR('abc def ghi', '[a<span class="token punctuation">-</span>z]<span class="token punctuation">+</span>') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> abc <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_SUBSTR</span><span class="token punctuation">(</span><span class="token string">'abc def ghi'</span><span class="token punctuation">,</span> <span class="token string">'[a-z]+'</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> REGEXP_SUBSTR('abc def ghi', '[a<span class="token punctuation">-</span>z]<span class="token punctuation">+</span>', 1, 3) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ghi <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="regexp-syntax">
</a>
Regular Expression Syntax
</h4>
</div>
</div>
</div>
<p>
A regular expression describes a set of strings. The simplest
regular expression is one that has no special characters in
it. For example, the regular expression
<code class="literal">
hello
</code>
matches
<code class="literal">
hello
</code>
and
nothing else.
</p>
<p>
Nontrivial regular expressions use certain special constructs
so that they can match more than one string. For example, the
regular expression
<code class="literal">
hello|world
</code>
contains the
<code class="literal">
|
</code>
alternation operator and matches either
the
<code class="literal">
hello
</code>
or
<code class="literal">
world
</code>
.
</p>
<p>
As a more complex example, the regular expression
<code class="literal">
B[an]*s
</code>
matches any of the strings
<code class="literal">
Bananas
</code>
,
<code class="literal">
Baaaaas
</code>
,
<code class="literal">
Bs
</code>
, and any other string starting with a
<code class="literal">
B
</code>
, ending with an
<code class="literal">
s
</code>
, and
containing any number of
<code class="literal">
a
</code>
or
<code class="literal">
n
</code>
characters in between.
</p>
<p>
The following list covers some of the basic special characters
and constructs that can be used in regular expressions. For
information about the full regular expression syntax supported
by the ICU library used to implement regular expression
support, visit the
<a class="ulink" href="https://unicode-org.github.io/icu/userguide/" target="_blank">
International Components for Unicode web site
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
^
</code>
</p>
<p>
Match the beginning of a string.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa11036312"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'fo\nfo'</span><span class="token punctuation">,</span> <span class="token string">'^fo$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'fofo'</span><span class="token punctuation">,</span> <span class="token string">'^fo'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
$
</code>
</p>
<p>
Match the end of a string.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa91304811"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'fo\no'</span><span class="token punctuation">,</span> <span class="token string">'^fo\no$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'fo\no'</span><span class="token punctuation">,</span> <span class="token string">'^fo$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
.
</code>
</p>
<p>
Match any character (including carriage return and
newline, although to match these in the middle of a
string, the
<code class="literal">
m
</code>
(multiple line)
match-control character or the
<code class="literal">
(?m)
</code>
within-pattern modifier must be given).
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa84742501"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'fofo'</span><span class="token punctuation">,</span> <span class="token string">'^f.*$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'fo\r\nfo'</span><span class="token punctuation">,</span> <span class="token string">'^f.*$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'fo\r\nfo'</span><span class="token punctuation">,</span> <span class="token string">'^f.*$'</span><span class="token punctuation">,</span> <span class="token string">'m'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'fo\r\nfo'</span><span class="token punctuation">,</span> <span class="token string">'(?m)^f.*$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
a*
</code>
</p>
<p>
Match any sequence of zero or more
<code class="literal">
a
</code>
characters.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa70442481"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'Ban'</span><span class="token punctuation">,</span> <span class="token string">'^Ba*n'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'Baaan'</span><span class="token punctuation">,</span> <span class="token string">'^Ba*n'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'Bn'</span><span class="token punctuation">,</span> <span class="token string">'^Ba*n'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
a+
</code>
</p>
<p>
Match any sequence of one or more
<code class="literal">
a
</code>
characters.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa69446014"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'Ban'</span><span class="token punctuation">,</span> <span class="token string">'^Ba+n'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'Bn'</span><span class="token punctuation">,</span> <span class="token string">'^Ba+n'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
a?
</code>
</p>
<p>
Match either zero or one
<code class="literal">
a
</code>
character.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa38834136"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'Bn'</span><span class="token punctuation">,</span> <span class="token string">'^Ba?n'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'Ban'</span><span class="token punctuation">,</span> <span class="token string">'^Ba?n'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'Baan'</span><span class="token punctuation">,</span> <span class="token string">'^Ba?n'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
de|abc
</code>
</p>
<p>
Alternation; match either of the sequences
<code class="literal">
de
</code>
or
<code class="literal">
abc
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa46986600"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'pi'</span><span class="token punctuation">,</span> <span class="token string">'pi|apa'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'axe'</span><span class="token punctuation">,</span> <span class="token string">'pi|apa'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'apa'</span><span class="token punctuation">,</span> <span class="token string">'pi|apa'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'apa'</span><span class="token punctuation">,</span> <span class="token string">'^(pi|apa)$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'pi'</span><span class="token punctuation">,</span> <span class="token string">'^(pi|apa)$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'pix'</span><span class="token punctuation">,</span> <span class="token string">'^(pi|apa)$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
(abc)*
</code>
</p>
<p>
Match zero or more instances of the sequence
<code class="literal">
abc
</code>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa17589560"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'pi'</span><span class="token punctuation">,</span> <span class="token string">'^(pi)*$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'pip'</span><span class="token punctuation">,</span> <span class="token string">'^(pi)*$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'pipi'</span><span class="token punctuation">,</span> <span class="token string">'^(pi)*$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
{1}
</code>
,
<code class="literal">
{2,3}
</code>
</p>
<p>
Repetition;
<code class="literal">
{
<em class="replaceable">
<code>
n
</code>
</em>
}
</code>
and
<code class="literal">
{
<em class="replaceable">
<code>
m
</code>
</em>
,
<em class="replaceable">
<code>
n
</code>
</em>
}
</code>
notation provide a more general way of writing regular
expressions that match many occurrences of the previous
atom (or
<span class="quote">
“
<span class="quote">
piece
</span>
”
</span>
) of the pattern.
<em class="replaceable">
<code>
m
</code>
</em>
and
<em class="replaceable">
<code>
n
</code>
</em>
are integers.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
a*
</code>
</p>
<p>
Can be written as
<code class="literal">
a{0,}
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
a+
</code>
</p>
<p>
Can be written as
<code class="literal">
a{1,}
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
a?
</code>
</p>
<p>
Can be written as
<code class="literal">
a{0,1}
</code>
.
</p>
</li>
</ul>
</div>
<p>
To be more precise,
<code class="literal">
a{
<em class="replaceable">
<code>
n
</code>
</em>
}
</code>
matches
exactly
<em class="replaceable">
<code>
n
</code>
</em>
instances of
<code class="literal">
a
</code>
.
<code class="literal">
a{
<em class="replaceable">
<code>
n
</code>
</em>
,}
</code>
matches
<em class="replaceable">
<code>
n
</code>
</em>
or more instances of
<code class="literal">
a
</code>
.
<code class="literal">
a{
<em class="replaceable">
<code>
m
</code>
</em>
,
<em class="replaceable">
<code>
n
</code>
</em>
}
</code>
matches
<em class="replaceable">
<code>
m
</code>
</em>
through
<em class="replaceable">
<code>
n
</code>
</em>
instances of
<code class="literal">
a
</code>
, inclusive. If both
<em class="replaceable">
<code>
m
</code>
</em>
and
<em class="replaceable">
<code>
n
</code>
</em>
are given,
<em class="replaceable">
<code>
m
</code>
</em>
must be less than or equal to
<em class="replaceable">
<code>
n
</code>
</em>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa30274226"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'abcde'</span><span class="token punctuation">,</span> <span class="token string">'a[bcd]{2}e'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'abcde'</span><span class="token punctuation">,</span> <span class="token string">'a[bcd]{3}e'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'abcde'</span><span class="token punctuation">,</span> <span class="token string">'a[bcd]{1,10}e'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
[a-dX]
</code>
,
<code class="literal">
[^a-dX]
</code>
</p>
<p>
Matches any character that is (or is not, if
<code class="literal">
^
</code>
is used) either
<code class="literal">
a
</code>
,
<code class="literal">
b
</code>
,
<code class="literal">
c
</code>
,
<code class="literal">
d
</code>
or
<code class="literal">
X
</code>
. A
<code class="literal">
-
</code>
character between two other
characters forms a range that matches all characters from
the first character to the second. For example,
<code class="literal">
[0-9]
</code>
matches any decimal digit. To
include a literal
<code class="literal">
]
</code>
character, it must
immediately follow the opening bracket
<code class="literal">
[
</code>
. To include a literal
<code class="literal">
-
</code>
character, it must be written first
or last. Any character that does not have a defined
special meaning inside a
<code class="literal">
[]
</code>
pair
matches only itself.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa37885166"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'aXbc'</span><span class="token punctuation">,</span> <span class="token string">'[a-dXYZ]'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'aXbc'</span><span class="token punctuation">,</span> <span class="token string">'^[a-dXYZ]$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'aXbc'</span><span class="token punctuation">,</span> <span class="token string">'^[a-dXYZ]+$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'aXbc'</span><span class="token punctuation">,</span> <span class="token string">'^[^a-dXYZ]+$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'gheis'</span><span class="token punctuation">,</span> <span class="token string">'^[^a-dXYZ]+$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'gheisa'</span><span class="token punctuation">,</span> <span class="token string">'^[^a-dXYZ]+$'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
[=character_class=]
</code>
</p>
<p>
Within a bracket expression (written using
<code class="literal">
[
</code>
and
<code class="literal">
]
</code>
),
<code class="literal">
[=character_class=]
</code>
represents an
equivalence class. It matches all characters with the same
collation value, including itself. For example, if
<code class="literal">
o
</code>
and
<code class="literal">
(+)
</code>
are the
members of an equivalence class,
<code class="literal">
[[=o=]]
</code>
,
<code class="literal">
[[=(+)=]]
</code>
,
and
<code class="literal">
[o(+)]
</code>
are all synonymous. An
equivalence class may not be used as an endpoint of a
range.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
[:character_class:]
</code>
</p>
<p>
Within a bracket expression (written using
<code class="literal">
[
</code>
and
<code class="literal">
]
</code>
),
<code class="literal">
[:character_class:]
</code>
represents a
character class that matches all characters belonging to
that class. The following table lists the standard class
names. These names stand for the character classes defined
in the
<code class="literal">
ctype(3)
</code>
manual page. A
particular locale may provide other class names. A
character class may not be used as an endpoint of a range.
</p>
<div class="informaltable">
<table summary="Character class names and the meaning of each class.">
<colgroup>
<col style="width: 20%"/>
<col style="width: 80%"/>
</colgroup>
<thead>
<tr>
<th>
Character Class Name
</th>
<th>
Meaning
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<code class="literal">
alnum
</code>
</td>
<td>
Alphanumeric characters
</td>
</tr>
<tr>
<td>
<code class="literal">
alpha
</code>
</td>
<td>
Alphabetic characters
</td>
</tr>
<tr>
<td>
<code class="literal">
blank
</code>
</td>
<td>
Whitespace characters
</td>
</tr>
<tr>
<td>
<code class="literal">
cntrl
</code>
</td>
<td>
Control characters
</td>
</tr>
<tr>
<td>
<code class="literal">
digit
</code>
</td>
<td>
Digit characters
</td>
</tr>
<tr>
<td>
<code class="literal">
graph
</code>
</td>
<td>
Graphic characters
</td>
</tr>
<tr>
<td>
<code class="literal">
lower
</code>
</td>
<td>
Lowercase alphabetic characters
</td>
</tr>
<tr>
<td>
<code class="literal">
print
</code>
</td>
<td>
Graphic or space characters
</td>
</tr>
<tr>
<td>
<code class="literal">
punct
</code>
</td>
<td>
Punctuation characters
</td>
</tr>
<tr>
<td>
<code class="literal">
space
</code>
</td>
<td>
Space, tab, newline, and carriage return
</td>
</tr>
<tr>
<td>
<code class="literal">
upper
</code>
</td>
<td>
Uppercase alphabetic characters
</td>
</tr>
<tr>
<td>
<code class="literal">
xdigit
</code>
</td>
<td>
Hexadecimal digit characters
</td>
</tr>
</tbody>
</table>
</div>
<div class="informaltable">
<table cellpadding="0" cellspacing="0" style="position: fixed; top: 0px; display: none; left: 431px; width: 709px;">
<thead>
<tr>
<th style="width: 141.594px;">
Character Class Name
</th>
<th style="width: 566.406px;">
Meaning
</th>
</tr>
</thead>
</table>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa59116385"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'justalnums'</span><span class="token punctuation">,</span> <span class="token string">'[[:alnum:]]+'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'!!'</span><span class="token punctuation">,</span> <span class="token string">'[[:alnum:]]+'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
To use a literal instance of a special character in a regular
expression, precede it by two backslash (\) characters. The
MySQL parser interprets one of the backslashes, and the
regular expression library interprets the other. For example,
to match the string
<code class="literal">
1+2
</code>
that contains the
special
<code class="literal">
+
</code>
character, only the last of the
following regular expressions is the correct one:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa94567478"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'1+2'</span><span class="token punctuation">,</span> <span class="token string">'1+2'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'1+2'</span><span class="token punctuation">,</span> <span class="token string">'1\+2'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">REGEXP_LIKE</span><span class="token punctuation">(</span><span class="token string">'1+2'</span><span class="token punctuation">,</span> <span class="token string">'1\\+2'</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token operator">-</span><span class="token operator">></span> <span class="token number">1</span></code></pre>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="regexp-resource-control">
</a>
Regular Expression Resource Control
</h4>
</div>
</div>
</div>
<p>
<a class="link" href="regexp.html#function_regexp-like">
<code class="literal">
REGEXP_LIKE()
</code>
</a>
and similar
functions use resources that can be controlled by setting
system variables:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The match engine uses memory for its internal stack. To
control the maximum available memory for the stack in
bytes, set the
<a class="link" href="server-system-variables.html#sysvar_regexp_stack_limit">
<code class="literal">
regexp_stack_limit
</code>
</a>
system
variable.
</p>
</li>
<li class="listitem">
<p>
The match engine operates in steps. To control the maximum
number of steps performed by the engine (and thus
indirectly the execution time), set the
<a class="link" href="server-system-variables.html#sysvar_regexp_time_limit">
<code class="literal">
regexp_time_limit
</code>
</a>
system
variable. Because this limit is expressed as number of
steps, it affects execution time only indirectly.
Typically, it is on the order of milliseconds.
</p>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/component-statements.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="component-statements">
</a>
15.7.4 Component, Plugin, and Loadable Function Statements
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="create-function-loadable.html">
15.7.4.1 CREATE FUNCTION Statement for Loadable Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="drop-function-loadable.html">
15.7.4.2 DROP FUNCTION Statement for Loadable Functions
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="install-component.html">
15.7.4.3 INSTALL COMPONENT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="install-plugin.html">
15.7.4.4 INSTALL PLUGIN Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="uninstall-component.html">
15.7.4.5 UNINSTALL COMPONENT Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="uninstall-plugin.html">
15.7.4.6 UNINSTALL PLUGIN Statement
</a>
</span>
</dt>
</dl>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/privilege-changes.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="privilege-changes">
</a>
8.2.13 When Privilege Changes Take Effect
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045248776432">
</a>
<a class="indexterm" name="idm46045248774976">
</a>
<p>
If the
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
server is started without the
<a class="link" href="server-options.html#option_mysqld_skip-grant-tables">
<code class="option">
--skip-grant-tables
</code>
</a>
option, it
reads all grant table contents into memory during its startup
sequence. The in-memory tables become effective for access control
at that point.
</p>
<p>
If you modify the grant tables indirectly using an
account-management statement, the server notices these changes and
loads the grant tables into memory again immediately.
Account-management statements are described in
<a class="xref" href="account-management-statements.html" title="15.7.1 Account Management Statements">
Section 15.7.1, “Account Management Statements”
</a>
. Examples include
<a class="link" href="grant.html" title="15.7.1.6 GRANT Statement">
<code class="literal">
GRANT
</code>
</a>
,
<a class="link" href="revoke.html" title="15.7.1.8 REVOKE Statement">
<code class="literal">
REVOKE
</code>
</a>
,
<a class="link" href="set-password.html" title="15.7.1.10 SET PASSWORD Statement">
<code class="literal">
SET
PASSWORD
</code>
</a>
, and
<a class="link" href="rename-user.html" title="15.7.1.7 RENAME USER Statement">
<code class="literal">
RENAME
USER
</code>
</a>
.
</p>
<p>
If you modify the grant tables directly using statements such as
<a class="link" href="insert.html" title="15.2.7 INSERT Statement">
<code class="literal">
INSERT
</code>
</a>
,
<a class="link" href="update.html" title="15.2.17 UPDATE Statement">
<code class="literal">
UPDATE
</code>
</a>
, or
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
(which is not recommended),
the changes have no effect on privilege checking until you either
tell the server to reload the tables or restart it. Thus, if you
change the grant tables directly but forget to reload them, the
changes have
<span class="emphasis">
<em>
no effect
</em>
</span>
until you restart the
server. This may leave you wondering why your changes seem to make
no difference!
</p>
<p>
To tell the server to reload the grant tables, perform a
flush-privileges operation. This can be done by issuing a
<a class="link" href="flush.html#flush-privileges">
<code class="literal">
FLUSH PRIVILEGES
</code>
</a>
statement or by
executing a
<a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program">
<span class="command">
<strong>
mysqladmin flush-privileges
</strong>
</span>
</a>
or
<a class="link" href="mysqladmin.html" title="6.5.2 mysqladmin — A MySQL Server Administration Program">
<span class="command">
<strong>
mysqladmin reload
</strong>
</span>
</a>
command.
</p>
<p>
A grant table reload affects privileges for each existing client
session as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Table and column privilege changes take effect with the
client's next request.
</p>
</li>
<li class="listitem">
<p>
Database privilege changes take effect the next time the
client executes a
<code class="literal">
USE
<em class="replaceable">
<code>
db_name
</code>
</em>
</code>
statement.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Client applications may cache the database name; thus, this
effect may not be visible to them without actually changing
to a different database.
</p>
</div>
</li>
<li class="listitem">
<p>
Static global privileges and passwords are unaffected for a
connected client. These changes take effect only in sessions
for subsequent connections. Changes to dynamic global
privileges apply immediately. For information about the
differences between static and dynamic privileges, see
<a class="xref" href="privileges-provided.html#static-dynamic-privileges" title="Static Versus Dynamic Privileges">
Static Versus Dynamic Privileges
</a>
.)
</p>
</li>
</ul>
</div>
<p>
Changes to the set of active roles within a session take effect
immediately, for that session only. The
<a class="link" href="set-role.html" title="15.7.1.11 SET ROLE Statement">
<code class="literal">
SET
ROLE
</code>
</a>
statement performs session role activation and
deactivation (see
<a class="xref" href="set-role.html" title="15.7.1.11 SET ROLE Statement">
Section 15.7.1.11, “SET ROLE Statement”
</a>
).
</p>
<p>
If the server is started with the
<a class="link" href="server-options.html#option_mysqld_skip-grant-tables">
<code class="option">
--skip-grant-tables
</code>
</a>
option, it does
not read the grant tables or implement any access control. Any
user can connect and perform any operation,
<span class="emphasis">
<em>
which is
insecure.
</em>
</span>
To cause a server thus started to read the
tables and enable access checking, flush the privileges.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/deleting-from-related-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="deleting-from-related-tables">
</a>
B.3.4.6 Deleting Rows from Related Tables
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045053488688">
</a>
<a class="indexterm" name="idm46045053487232">
</a>
<a class="indexterm" name="idm46045053485744">
</a>
<p>
If the total length of the
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
statement for
<code class="literal">
related_table
</code>
is more than the default
value of the
<a class="link" href="server-system-variables.html#sysvar_max_allowed_packet">
<code class="literal">
max_allowed_packet
</code>
</a>
system
variable, you should split it into smaller parts and execute
multiple
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
statements. You
probably get the fastest
<a class="link" href="delete.html" title="15.2.2 DELETE Statement">
<code class="literal">
DELETE
</code>
</a>
by specifying only 100 to 1,000
<code class="literal">
related_column
</code>
values per statement if the
<code class="literal">
related_column
</code>
is indexed. If the
<code class="literal">
related_column
</code>
is not indexed, the speed is
independent of the number of arguments in the
<code class="literal">
IN
</code>
clause.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-tp-thread-group-state-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-tp-thread-group-state-table">
</a>
29.12.16.2 The tp_thread_group_state Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045069841152">
</a>
<a class="indexterm" name="idm46045069839648">
</a>
<p>
The
<a class="link" href="performance-schema-tp-thread-group-state-table.html" title="29.12.16.2 The tp_thread_group_state Table">
<code class="literal">
tp_thread_group_state
</code>
</a>
table
has one row per thread group in the thread pool. Each row
provides information about the current state of a group.
</p>
<p>
The
<a class="link" href="performance-schema-tp-thread-group-state-table.html" title="29.12.16.2 The tp_thread_group_state Table">
<code class="literal">
tp_thread_group_state
</code>
</a>
table
has these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
TP_GROUP_ID
</code>
</p>
<p>
The thread group ID. This is a unique key within the
table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CONSUMER THREADS
</code>
</p>
<p>
The number of consumer threads. There is at most one
thread ready to start executing if the active threads
become stalled or blocked.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
RESERVE_THREADS
</code>
</p>
<p>
The number of threads in the reserved state. This means
that they are not started until there is a need to wake a
new thread and there is no consumer thread. This is where
most threads end up when the thread group has created more
threads than needed for normal operation. Often a thread
group needs additional threads for a short while and then
does not need them again for a while. In this case, they
go into the reserved state and remain until needed again.
They take up some extra memory resources, but no extra
computing resources.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CONNECT_THREAD_COUNT
</code>
</p>
<p>
The number of threads that are processing or waiting to
process connection initialization and authentication.
There can be a maximum of four connection threads per
thread group; these threads expire after a period of
inactivity.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CONNECTION_COUNT
</code>
</p>
<p>
The number of connections using this thread group.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
QUEUED_QUERIES
</code>
</p>
<p>
The number of statements waiting in the high-priority
queue.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
QUEUED_TRANSACTIONS
</code>
</p>
<p>
The number of statements waiting in the low-priority
queue. These are the initial statements for transactions
that have not started, so they also represent queued
transactions.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
STALL_LIMIT
</code>
</p>
<p>
The value of the
<a class="link" href="server-system-variables.html#sysvar_thread_pool_stall_limit">
<code class="literal">
thread_pool_stall_limit
</code>
</a>
system variable for the thread group. This is the same
value for all thread groups.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
PRIO_KICKUP_TIMER
</code>
</p>
<p>
The value of the
<a class="link" href="server-system-variables.html#sysvar_thread_pool_prio_kickup_timer">
<code class="literal">
thread_pool_prio_kickup_timer
</code>
</a>
system variable for the thread group. This is the same
value for all thread groups.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ALGORITHM
</code>
</p>
<p>
The value of the
<a class="link" href="server-system-variables.html#sysvar_thread_pool_algorithm">
<code class="literal">
thread_pool_algorithm
</code>
</a>
system variable for the thread group. This is the same
value for all thread groups.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
THREAD_COUNT
</code>
</p>
<p>
The number of threads started in the thread pool as part
of this thread group.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ACTIVE_THREAD_COUNT
</code>
</p>
<p>
The number of threads active in executing statements.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
STALLED_THREAD_COUNT
</code>
</p>
<p>
The number of stalled statements in the thread group. A
stalled statement could be executing, but from a thread
pool perspective it is stalled and making no progress. A
long-running statement quickly ends up in this category.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
WAITING_THREAD_NUMBER
</code>
</p>
<p>
If there is a thread handling the polling of statements in
the thread group, this specifies the thread number within
this thread group. It is possible that this thread could
be executing a statement.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OLDEST_QUEUED
</code>
</p>
<p>
How long in milliseconds the oldest queued statement has
been waiting for execution.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MAX_THREAD_IDS_IN_GROUP
</code>
</p>
<p>
The maximum thread ID of the threads in the group. This is
the same as
<a class="link" href="aggregate-functions.html#function_max">
<code class="literal">
MAX(TP_THREAD_NUMBER)
</code>
</a>
for
the threads when selected from the
<a class="link" href="performance-schema-tp-thread-state-table.html" title="29.12.16.4 The tp_thread_state Table">
<code class="literal">
tp_thread_state
</code>
</a>
table. That
is, these two queries are equivalent:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa20801702"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> TP_GROUP_ID<span class="token punctuation">,</span> MAX_THREAD_IDS_IN_GROUP
<span class="token keyword">FROM</span> tp_thread_group_state<span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> TP_GROUP_ID<span class="token punctuation">,</span> <span class="token function">MAX</span><span class="token punctuation">(</span>TP_THREAD_NUMBER<span class="token punctuation">)</span>
<span class="token keyword">FROM</span> tp_thread_state <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> TP_GROUP_ID<span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
EFFECTIVE_MAX_TRANSACTIONS_LIMIT
</code>
</p>
<p>
The effective
<code class="literal">
max_transactions_limit_per_tg
</code>
value for
the group.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
NUM_QUERY_THREADS
</code>
</p>
<p>
The number of worker threads in the group.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TIME_OF_LAST_THREAD_CREATION
</code>
</p>
<p>
The point in time when the thread was last created.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
NUM_CONNECT_HANDLER_THREAD_IN_SLEEP
</code>
</p>
<p>
The number of inactive connection handler threads.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
THREADS_BOUND_TO_TRANSACTION
</code>
</p>
<p>
The number of threads in an active transaction, which must
be less than
<code class="literal">
thread_pool_max_transactions_limit
</code>
;
this is set only when
<code class="literal">
thread_pool_max_transactions_limit
</code>
is
not
<code class="literal">
0
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
QUERY_THREADS_COUNT
</code>
</p>
<p>
same as num_query_threads, but used for different
purposes?
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TIME_OF_EARLIEST_CON_EXPIRE
</code>
</p>
<p>
A timestamp showing the earliest point in time when a
connection is expected to expire.
</p>
</li>
</ul>
</div>
<p>
The
<a class="link" href="performance-schema-tp-thread-group-state-table.html" title="29.12.16.2 The tp_thread_group_state Table">
<code class="literal">
tp_thread_group_state
</code>
</a>
table
has one index; this is a unique index on the
<code class="literal">
TP_GROUP_ID
</code>
column.
</p>
<p>
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
is not permitted
for the
<a class="link" href="performance-schema-tp-thread-group-state-table.html" title="29.12.16.2 The tp_thread_group_state Table">
<code class="literal">
tp_thread_group_state
</code>
</a>
table.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-enterprise-backup.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="mysql-enterprise-backup">
</a>
32.1 MySQL Enterprise Backup Overview
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045060255056">
</a>
<a class="indexterm" name="idm46045060254016">
</a>
<a class="indexterm" name="idm46045060252944">
</a>
<p>
MySQL Enterprise Backup performs hot backup operations for MySQL databases. The
product is architected for efficient and reliable backups of
tables created by the InnoDB storage engine. For completeness, it
can also back up tables from MyISAM and other storage engines.
</p>
<p>
The following discussion briefly summarizes MySQL Enterprise Backup. For more
information, see the MySQL Enterprise Backup manual, available at
<a class="ulink" href="/doc/mysql-enterprise-backup/en/" target="_top">
https://dev.mysql.com/doc/mysql-enterprise-backup/en/
</a>
.
</p>
<p>
Hot backups are performed while the database is running and
applications are reading and writing to it. This type of backup
does not block normal database operations, and it captures even
changes that occur while the backup is happening. For these
reasons, hot backups are desirable when your database
<span class="quote">
“
<span class="quote">
grows
up
</span>
”
</span>
-- when the data is large enough that the backup takes
significant time, and when your data is important enough to your
business that you must capture every last change, without taking
your application, website, or web service offline.
</p>
<p>
MySQL Enterprise Backup does a hot backup of all tables that use the InnoDB storage
engine. For tables using MyISAM or other non-InnoDB storage
engines, it does a
<span class="quote">
“
<span class="quote">
warm
</span>
”
</span>
backup, where the database
continues to run, but those tables cannot be modified while being
backed up. For efficient backup operations, you can designate
InnoDB as the default storage engine for new tables, or convert
existing tables to use the InnoDB storage engine.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/json-table-functions.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="json-table-functions">
</a>
14.17.6 JSON Table Functions
</h3>
</div>
</div>
</div>
<p>
This section contains information about JSON functions that
convert JSON data to tabular data. MySQL 8.4 supports
one such function,
<code class="literal">
JSON_TABLE()
</code>
.
</p>
<p>
<a name="function_json-table">
</a>
<a class="link" href="json-table-functions.html#function_json-table">
<code class="literal">
JSON_TABLE(
<em class="replaceable">
<code>
expr
</code>
</em>
,
<em class="replaceable">
<code>
path
</code>
</em>
COLUMNS
(
<em class="replaceable">
<code>
column_list
</code>
</em>
) [AS]
<em class="replaceable">
<code>
alias
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045194660016">
</a>
<p>
Extracts data from a JSON document and returns it as a relational
table having the specified columns. The complete syntax for this
function is shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-clike"><div class="docs-select-all right" id="sa8508545"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-clike"><span class="token function">JSON_TABLE</span><span class="token punctuation">(</span>
<em class="replaceable">expr</em><span class="token punctuation">,</span>
<em class="replaceable">path</em> COLUMNS <span class="token punctuation">(</span><em class="replaceable">column_list</em><span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token punctuation">[</span>AS<span class="token punctuation">]</span> <em class="replaceable">alias</em>
<em class="replaceable">column_list</em><span class="token punctuation">:</span>
<em class="replaceable">column</em><span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">column</em><span class="token punctuation">]</span><span class="token punctuation">[</span><span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">]</span>
<em class="replaceable">column</em><span class="token punctuation">:</span>
<em class="replaceable">name</em> FOR ORDINALITY
<span class="token operator">|</span> <em class="replaceable">name</em> <em class="replaceable">type</em> PATH <em class="replaceable">string path</em> <span class="token punctuation">[</span><em class="replaceable">on_empty</em><span class="token punctuation">]</span> <span class="token punctuation">[</span><em class="replaceable">on_error</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <em class="replaceable">name</em> <em class="replaceable">type</em> EXISTS PATH <em class="replaceable">string path</em>
<span class="token operator">|</span> NESTED <span class="token punctuation">[</span>PATH<span class="token punctuation">]</span> <em class="replaceable">path</em> COLUMNS <span class="token punctuation">(</span><em class="replaceable">column_list</em><span class="token punctuation">)</span>
<em class="replaceable">on_empty</em><span class="token punctuation">:</span>
<span class="token punctuation">{</span>NULL <span class="token operator">|</span> DEFAULT <em class="replaceable">json_string</em> <span class="token operator">|</span> ERROR<span class="token punctuation">}</span> ON EMPTY
<em class="replaceable">on_error</em><span class="token punctuation">:</span>
<span class="token punctuation">{</span>NULL <span class="token operator">|</span> DEFAULT <em class="replaceable">json_string</em> <span class="token operator">|</span> ERROR<span class="token punctuation">}</span> ON ERROR</code></pre>
</div>
<p>
<em class="replaceable">
<code>
expr
</code>
</em>
: This is an expression that
returns JSON data. This can be a constant
(
<code class="literal">
'{"a":1}'
</code>
), a column
(
<code class="literal">
t1.json_data
</code>
, given table
<code class="literal">
t1
</code>
specified prior to
<code class="literal">
JSON_TABLE()
</code>
in the
<code class="literal">
FROM
</code>
clause), or a function call
(
<code class="literal">
JSON_EXTRACT(t1.json_data,'$.post.comments')
</code>
).
</p>
<p>
<em class="replaceable">
<code>
path
</code>
</em>
: A JSON path expression, which is
applied to the data source. We refer to the JSON value matching
the path as the
<span class="emphasis">
<em>
row source
</em>
</span>
; this is used to
generate a row of relational data. The
<code class="literal">
COLUMNS
</code>
clause evaluates the row source, finds specific JSON values within
the row source, and returns those JSON values as SQL values in
individual columns of a row of relational data.
</p>
<p>
The
<em class="replaceable">
<code>
alias
</code>
</em>
is required. The usual rules
for table aliases apply (see
<a class="xref" href="identifiers.html" title="11.2 Schema Object Names">
Section 11.2, “Schema Object Names”
</a>
).
</p>
<p>
This function compares column names in case-insensitive fashion.
</p>
<p>
<code class="literal">
JSON_TABLE()
</code>
supports four types of columns,
described in the following list:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
<code class="literal">
<em class="replaceable">
<code>
name
</code>
</em>
FOR
ORDINALITY
</code>
: This type enumerates rows in the
<code class="literal">
COLUMNS
</code>
clause; the column named
<em class="replaceable">
<code>
name
</code>
</em>
is a counter whose type is
<code class="literal">
UNSIGNED INT
</code>
, and whose initial value is 1.
This is equivalent to specifying a column as
<code class="literal">
AUTO_INCREMENT
</code>
in a
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
statement, and can
be used to distinguish parent rows with the same value for
multiple rows generated by a
<code class="literal">
NESTED [PATH]
</code>
clause.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<em class="replaceable">
<code>
name
</code>
</em>
<em class="replaceable">
<code>
type
</code>
</em>
PATH
<em class="replaceable">
<code>
string_path
</code>
</em>
[
<em class="replaceable">
<code>
on_empty
</code>
</em>
]
[
<em class="replaceable">
<code>
on_error
</code>
</em>
]
</code>
: Columns of
this type are used to extract values specified by
<em class="replaceable">
<code>
string_path
</code>
</em>
.
<em class="replaceable">
<code>
type
</code>
</em>
is a MySQL scalar data type
(that is, it cannot be an object or array).
<code class="literal">
JSON_TABLE()
</code>
extracts data as JSON then
coerces it to the column type, using the regular automatic
type conversion applying to JSON data in MySQL. A missing
value triggers the
<em class="replaceable">
<code>
on_empty
</code>
</em>
clause.
Saving an object or array triggers the optional
<em class="replaceable">
<code>
on error
</code>
</em>
clause; this also occurs
when an error takes place during coercion from the value saved
as JSON to the table column, such as trying to save the string
<code class="literal">
'asd'
</code>
to an integer column.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
<em class="replaceable">
<code>
name
</code>
</em>
<em class="replaceable">
<code>
type
</code>
</em>
EXISTS PATH
<em class="replaceable">
<code>
path
</code>
</em>
</code>
: This column returns
1 if any data is present at the location specified by
<em class="replaceable">
<code>
path
</code>
</em>
, and 0 otherwise.
<em class="replaceable">
<code>
type
</code>
</em>
can be any valid MySQL data
type, but should normally be specified as some variety of
<a class="link" href="integer-types.html" title="13.1.2 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT">
<code class="literal">
INT
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
NESTED [PATH]
<em class="replaceable">
<code>
path
</code>
</em>
COLUMNS
(
<em class="replaceable">
<code>
column_list
</code>
</em>
)
</code>
: This
flattens nested objects or arrays in JSON data into a single
row along with the JSON values from the parent object or
array. Using multiple
<code class="literal">
PATH
</code>
options allows
projection of JSON values from multiple levels of nesting into
a single row.
</p>
<p>
The
<em class="replaceable">
<code>
path
</code>
</em>
is relative to the parent
path row path of
<code class="literal">
JSON_TABLE()
</code>
, or the path
of the parent
<code class="literal">
NESTED [PATH]
</code>
clause in the
event of nested paths.
</p>
</li>
</ol>
</div>
<p>
<em class="replaceable">
<code>
on empty
</code>
</em>
, if specified, determines what
<code class="literal">
JSON_TABLE()
</code>
does in the event that data is
missing (depending on type). This clause is also triggered on a
column in a
<code class="literal">
NESTED PATH
</code>
clause when the latter
has no match and a
<code class="literal">
NULL
</code>
complemented row is
produced for it.
<em class="replaceable">
<code>
on empty
</code>
</em>
takes one of
the following values:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
NULL ON EMPTY
</code>
: The column is set to
<code class="literal">
NULL
</code>
; this is the default behavior.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
DEFAULT
<em class="replaceable">
<code>
json_string
</code>
</em>
ON
EMPTY
</code>
: the provided
<em class="replaceable">
<code>
json_string
</code>
</em>
is parsed as JSON, as
long as it is valid, and stored instead of the missing value.
Column type rules also apply to the default value.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ERROR ON EMPTY
</code>
: An error is thrown.
</p>
</li>
</ul>
</div>
<p>
If used,
<em class="replaceable">
<code>
on_error
</code>
</em>
takes one of the
following values with the corresponding result as shown here:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
NULL ON ERROR
</code>
: The column is set to
<code class="literal">
NULL
</code>
; this is the default behavior.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
DEFAULT
<em class="replaceable">
<code>
json string
</code>
</em>
ON
ERROR
</code>
: The
<em class="replaceable">
<code>
json_string
</code>
</em>
is
parsed as JSON (provided that it is valid) and stored instead
of the object or array.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ERROR ON ERROR
</code>
: An error is thrown.
</p>
</li>
</ul>
</div>
<p>
Specifying
<code class="literal">
ON ERROR
</code>
before
<code class="literal">
ON
EMPTY
</code>
is nonstandard and deprecated in MySQL; trying to
do so causes the server to issue a warning. Expect support for the
nonstandard syntax to be removed in a future version of MySQL.
</p>
<p>
When a value saved to a column is truncated, such as saving
3.14159 in a
<a class="link" href="fixed-point-types.html" title="13.1.3 Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC">
<code class="literal">
DECIMAL(10,1)
</code>
</a>
column,
a warning is issued independently of any
<code class="literal">
ON
ERROR
</code>
option. When multiple values are truncated in a
single statement, the warning is issued only once.
</p>
<p>
When the expression and path passed to this function resolve to
JSON null,
<code class="literal">
JSON_TABLE()
</code>
returns SQL
<code class="literal">
NULL
</code>
, in accordance with the SQL standard, as
shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa59487310"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span>
<span class="token prompt"> -></span> <span class="token keyword">FROM</span>
<span class="token prompt"> -></span> <span class="token keyword">JSON_TABLE</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> <span class="token string">'[ {"c1": null} ]'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token string">'$[*]'</span> <span class="token keyword">COLUMNS</span><span class="token punctuation">(</span> c1 <span class="token datatype">INT</span> <span class="token keyword">PATH</span> <span class="token string">'$.c1'</span> <span class="token keyword">ERROR</span> <span class="token keyword">ON</span> <span class="token keyword">ERROR</span> <span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span> <span class="token keyword">as</span> jt<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> c1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> NULL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
The following query demonstrates the use of
<code class="literal">
ON
EMPTY
</code>
and
<code class="literal">
ON ERROR
</code>
. The row
corresponding to
<code class="literal">
{"b":1}
</code>
is empty for the path
<code class="literal">
"$.a"
</code>
, and attempting to save
<code class="literal">
[1,2]
</code>
as a scalar produces an error; these rows
are highlighted in the output shown.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa15697702"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span>
<span class="token prompt"> -></span> <span class="token keyword">FROM</span>
<span class="token prompt"> -></span> <span class="token keyword">JSON_TABLE</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> <span class="token string">'[{"a":"3"},{"a":2},{"b":1},{"a":0},{"a":[1,2]}]'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token string">"$[*]"</span>
<span class="token prompt"> -></span> <span class="token keyword">COLUMNS</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> rowid <span class="token keyword">FOR</span> <span class="token keyword">ORDINALITY</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> ac <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token punctuation">)</span> <span class="token keyword">PATH</span> <span class="token string">"$.a"</span> <span class="token keyword">DEFAULT</span> <span class="token string">'111'</span> <span class="token keyword">ON</span> <span class="token keyword">EMPTY</span> <span class="token keyword">DEFAULT</span> <span class="token string">'999'</span> <span class="token keyword">ON</span> <span class="token keyword">ERROR</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> aj <span class="token datatype">JSON</span> <span class="token keyword">PATH</span> <span class="token string">"$.a"</span> <span class="token keyword">DEFAULT</span> <span class="token string">'{"x": 333}'</span> <span class="token keyword">ON</span> <span class="token keyword">EMPTY</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> bx <span class="token datatype">INT</span> <span class="token keyword">EXISTS</span> <span class="token keyword">PATH</span> <span class="token string">"$.b"</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span> <span class="token keyword">AS</span> tt<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> rowid <span class="token punctuation">|</span> ac <span class="token punctuation">|</span> aj <span class="token punctuation">|</span> bx <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> "3" <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation"></span><em><span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 111 <span class="token punctuation">|</span> {"x": 333} <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></em><span class="token punctuation"></span></span>
<span class="token output"><span class="token punctuation">|</span> 4 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation"></span><em><span class="token punctuation">|</span> 5 <span class="token punctuation">|</span> 999 <span class="token punctuation">|</span> [1, 2] <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></em><span class="token punctuation"></span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">5 rows in set (0.00 sec)</span></code></pre>
</div>
<p>
Column names are subject to the usual rules and limitations
governing table column names. See
<a class="xref" href="identifiers.html" title="11.2 Schema Object Names">
Section 11.2, “Schema Object Names”
</a>
.
</p>
<p>
All JSON and JSON path expressions are checked for validity; an
invalid expression of either type causes an error.
</p>
<p>
Each match for the
<em class="replaceable">
<code>
path
</code>
</em>
preceding the
<code class="literal">
COLUMNS
</code>
keyword maps to an individual row in
the result table. For example, the following query gives the
result shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa84892648"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span>
<span class="token prompt"> -></span> <span class="token keyword">FROM</span>
<span class="token prompt"> -></span> <span class="token keyword">JSON_TABLE</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> <span class="token string">'[{"x":2,"y":"8"},{"x":"3","y":"7"},{"x":"4","y":6}]'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token string">"$[*]"</span> <span class="token keyword">COLUMNS</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> xval <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token punctuation">)</span> <span class="token keyword">PATH</span> <span class="token string">"$.x"</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> yval <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token punctuation">)</span> <span class="token keyword">PATH</span> <span class="token string">"$.y"</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span> <span class="token keyword">AS</span> jt1<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> xval <span class="token punctuation">|</span> yval <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 8 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 7 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 4 <span class="token punctuation">|</span> 6 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
The expression
<code class="literal">
"$[*]"
</code>
matches each element of
the array. You can filter the rows in the result by modifying the
path. For example, using
<code class="literal">
"$[1]"
</code>
limits
extraction to the second element of the JSON array used as the
source, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa75478032"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span>
<span class="token prompt"> -></span> <span class="token keyword">FROM</span>
<span class="token prompt"> -></span> <span class="token keyword">JSON_TABLE</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> <span class="token string">'[{"x":2,"y":"8"},{"x":"3","y":"7"},{"x":"4","y":6}]'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token string">"$[1]"</span> <span class="token keyword">COLUMNS</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> xval <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token punctuation">)</span> <span class="token keyword">PATH</span> <span class="token string">"$.x"</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> yval <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">100</span><span class="token punctuation">)</span> <span class="token keyword">PATH</span> <span class="token string">"$.y"</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span> <span class="token keyword">AS</span> jt1<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> xval <span class="token punctuation">|</span> yval <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 7 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Within a column definition,
<code class="literal">
"$"
</code>
passes the
entire match to the column;
<code class="literal">
"$.x"
</code>
and
<code class="literal">
"$.y"
</code>
pass only the values corresponding to the
keys
<code class="literal">
x
</code>
and
<code class="literal">
y
</code>
, respectively,
within that match. For more information, see
<a class="xref" href="json.html#json-path-syntax" title="JSON Path Syntax">
JSON Path Syntax
</a>
.
</p>
<p>
<code class="literal">
NESTED PATH
</code>
(or simply
<code class="literal">
NESTED
</code>
;
<code class="literal">
PATH
</code>
is optional)
produces a set of records for each match in the
<code class="literal">
COLUMNS
</code>
clause to which it belongs. If there is
no match, all columns of the nested path are set to
<code class="literal">
NULL
</code>
. This implements an outer join between the
topmost clause and
<code class="literal">
NESTED [PATH]
</code>
. An inner join
can be emulated by applying a suitable condition in the
<code class="literal">
WHERE
</code>
clause, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa40620500"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span>
<span class="token prompt"> -></span> <span class="token keyword">FROM</span>
<span class="token prompt"> -></span> <span class="token keyword">JSON_TABLE</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> <span class="token string">'[ {"a": 1, "b": [11,111]}, {"a": 2, "b": [22,222]}, {"a":3}]'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token string">'$[*]'</span> <span class="token keyword">COLUMNS</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> a <span class="token datatype">INT</span> <span class="token keyword">PATH</span> <span class="token string">'$.a'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">NESTED</span> <span class="token keyword">PATH</span> <span class="token string">'$.b[*]'</span> <span class="token keyword">COLUMNS</span> <span class="token punctuation">(</span>b <span class="token datatype">INT</span> <span class="token keyword">PATH</span> <span class="token string">'$'</span><span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span> <span class="token keyword">AS</span> jt
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> b <span class="token operator">IS</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> a <span class="token punctuation">|</span> b <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 11 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 111 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 22 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 222 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Sibling nested paths—that is, two or more instances of
<code class="literal">
NESTED [PATH]
</code>
in the same
<code class="literal">
COLUMNS
</code>
clause—are processed one after
another, one at a time. While one nested path is producing
records, columns of any sibling nested path expressions are set to
<code class="literal">
NULL
</code>
. This means that the total number of
records for a single match within a single containing
<code class="literal">
COLUMNS
</code>
clause is the sum and not the product
of all records produced by
<code class="literal">
NESTED [PATH]
</code>
modifiers, as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa55342212"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span>
<span class="token prompt"> -></span> <span class="token keyword">FROM</span>
<span class="token prompt"> -></span> <span class="token keyword">JSON_TABLE</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> <span class="token string">'[{"a": 1, "b": [11,111]}, {"a": 2, "b": [22,222]}]'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token string">'$[*]'</span> <span class="token keyword">COLUMNS</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> a <span class="token datatype">INT</span> <span class="token keyword">PATH</span> <span class="token string">'$.a'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">NESTED</span> <span class="token keyword">PATH</span> <span class="token string">'$.b[*]'</span> <span class="token keyword">COLUMNS</span> <span class="token punctuation">(</span>b1 <span class="token datatype">INT</span> <span class="token keyword">PATH</span> <span class="token string">'$'</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">NESTED</span> <span class="token keyword">PATH</span> <span class="token string">'$.b[*]'</span> <span class="token keyword">COLUMNS</span> <span class="token punctuation">(</span>b2 <span class="token datatype">INT</span> <span class="token keyword">PATH</span> <span class="token string">'$'</span><span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span> <span class="token keyword">AS</span> jt<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> a <span class="token punctuation">|</span> b1 <span class="token punctuation">|</span> b2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 11 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 111 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 11 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 111 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 22 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 222 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 22 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span> 222 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
A
<code class="literal">
FOR ORDINALITY
</code>
column enumerates records
produced by the
<code class="literal">
COLUMNS
</code>
clause, and can be used
to distinguish parent records of a nested path, especially if
values in parent records are the same, as can be seen here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa71578329"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span>
<span class="token prompt"> -></span> <span class="token keyword">FROM</span>
<span class="token prompt"> -></span> <span class="token keyword">JSON_TABLE</span><span class="token punctuation">(</span>
<span class="token prompt"> -></span> <span class="token string">'[{"a": "a_val",
'</span><span class="token operator">></span> <span class="token string">"b"</span>: <span class="token punctuation">[</span>{<span class="token string">"c"</span>: <span class="token string">"c_val"</span><span class="token punctuation">,</span> <span class="token string">"l"</span>: <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">]</span>}<span class="token punctuation">]</span>}<span class="token punctuation">,</span>
<span class="token string">'> {"a": "a_val",
'</span><span class="token operator">></span> <span class="token string">"b"</span>: <span class="token punctuation">[</span>{<span class="token string">"c"</span>: <span class="token string">"c_val"</span><span class="token punctuation">,</span><span class="token string">"l"</span>: <span class="token punctuation">[</span><span class="token number">11</span><span class="token punctuation">]</span>}<span class="token punctuation">,</span> {<span class="token string">"c"</span>: <span class="token string">"c_val"</span><span class="token punctuation">,</span> <span class="token string">"l"</span>: <span class="token punctuation">[</span><span class="token number">22</span><span class="token punctuation">]</span>}<span class="token punctuation">]</span>}<span class="token punctuation">]</span><span class="token string">',
-> '</span>$<span class="token punctuation">[</span><span class="token operator">*</span><span class="token punctuation">]</span><span class="token string">' COLUMNS(
-> top_ord FOR ORDINALITY,
-> apath VARCHAR(10) PATH '</span>$<span class="token punctuation">.</span>a<span class="token string">',
-> NESTED PATH '</span>$<span class="token punctuation">.</span>b<span class="token punctuation">[</span><span class="token operator">*</span><span class="token punctuation">]</span><span class="token string">' COLUMNS (
-> bpath VARCHAR(10) PATH '</span>$<span class="token punctuation">.</span>c<span class="token string">',
-> ord FOR ORDINALITY,
-> NESTED PATH '</span>$<span class="token punctuation">.</span>l<span class="token punctuation">[</span><span class="token operator">*</span><span class="token punctuation">]</span><span class="token string">' COLUMNS (lpath varchar(10) PATH '</span>$'<span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token punctuation">)</span> <span class="token keyword">as</span> jt<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> top_ord <span class="token punctuation">|</span> apath <span class="token punctuation">|</span> bpath <span class="token punctuation">|</span> ord <span class="token punctuation">|</span> lpath <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> a_val <span class="token punctuation">|</span> c_val <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> a_val <span class="token punctuation">|</span> c_val <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> a_val <span class="token punctuation">|</span> c_val <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 11 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> a_val <span class="token punctuation">|</span> c_val <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 22 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
The source document contains an array of two elements; each of
these elements produces two rows. The values of
<code class="literal">
apath
</code>
and
<code class="literal">
bpath
</code>
are the same
over the entire result set; this means that they cannot be used to
determine whether
<code class="literal">
lpath
</code>
values came from the
same or different parents. The value of the
<code class="literal">
ord
</code>
column remains the same as the set of records having
<code class="literal">
top_ord
</code>
equal to 1, so these two values are
from a single object. The remaining two values are from different
objects, since they have different values in the
<code class="literal">
ord
</code>
column.
</p>
<p>
Normally, you cannot join a derived table which depends on columns
of preceding tables in the same
<code class="literal">
FROM
</code>
clause.
MySQL, per the SQL standard, makes an exception for table
functions; these are considered lateral derived tables. This is
implicit, and for this reason is not allowed before
<code class="literal">
JSON_TABLE()
</code>
, also according to the standard.
</p>
<p>
Suppose you have a table
<code class="literal">
t1
</code>
created and
populated using the statements shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa69359500"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span>c1 <span class="token datatype">INT</span><span class="token punctuation">,</span> c2 <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">,</span> c3 <span class="token datatype">JSON</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">VALUES</span>
<span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">'z'</span><span class="token punctuation">,</span> <span class="token function">JSON_OBJECT</span><span class="token punctuation">(</span><span class="token string">'a'</span><span class="token punctuation">,</span> <span class="token number">23</span><span class="token punctuation">,</span> <span class="token string">'b'</span><span class="token punctuation">,</span> <span class="token number">27</span><span class="token punctuation">,</span> <span class="token string">'c'</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">'y'</span><span class="token punctuation">,</span> <span class="token function">JSON_OBJECT</span><span class="token punctuation">(</span><span class="token string">'a'</span><span class="token punctuation">,</span> <span class="token number">44</span><span class="token punctuation">,</span> <span class="token string">'b'</span><span class="token punctuation">,</span> <span class="token number">22</span><span class="token punctuation">,</span> <span class="token string">'c'</span><span class="token punctuation">,</span> <span class="token number">11</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token string">'x'</span><span class="token punctuation">,</span> <span class="token function">JSON_OBJECT</span><span class="token punctuation">(</span><span class="token string">'b'</span><span class="token punctuation">,</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token string">'c'</span><span class="token punctuation">,</span> <span class="token number">15</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">3</span><span class="token punctuation">,</span> <span class="token string">'w'</span><span class="token punctuation">,</span> <span class="token function">JSON_OBJECT</span><span class="token punctuation">(</span><span class="token string">'a'</span><span class="token punctuation">,</span> <span class="token number">5</span><span class="token punctuation">,</span> <span class="token string">'b'</span><span class="token punctuation">,</span> <span class="token number">6</span><span class="token punctuation">,</span> <span class="token string">'c'</span><span class="token punctuation">,</span> <span class="token number">7</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">,</span>
<span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">,</span> <span class="token string">'v'</span><span class="token punctuation">,</span> <span class="token function">JSON_OBJECT</span><span class="token punctuation">(</span><span class="token string">'a'</span><span class="token punctuation">,</span> <span class="token number">123</span><span class="token punctuation">,</span> <span class="token string">'c'</span><span class="token punctuation">,</span> <span class="token number">1111</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token punctuation">;</span></code></pre>
</div>
<p>
You can then execute joins, such as this one, in which
<code class="literal">
JSON_TABLE()
</code>
acts as a derived table while at
the same time it refers to a column in a previously referenced
table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa52439386"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">,</span> <span class="token function">JSON_EXTRACT</span><span class="token punctuation">(</span>c3<span class="token punctuation">,</span> <span class="token string">'$.*'</span><span class="token punctuation">)</span>
<span class="token keyword">FROM</span> t1 <span class="token keyword">AS</span> m
<span class="token keyword">JOIN</span>
<span class="token keyword">JSON_TABLE</span><span class="token punctuation">(</span>
m<span class="token punctuation">.</span>c3<span class="token punctuation">,</span>
<span class="token string">'$.*'</span>
<span class="token keyword">COLUMNS</span><span class="token punctuation">(</span>
<span class="token keyword">at</span> <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">PATH</span> <span class="token string">'$.a'</span> <span class="token keyword">DEFAULT</span> <span class="token string">'1'</span> <span class="token keyword">ON</span> <span class="token keyword">EMPTY</span><span class="token punctuation">,</span>
bt <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">PATH</span> <span class="token string">'$.b'</span> <span class="token keyword">DEFAULT</span> <span class="token string">'2'</span> <span class="token keyword">ON</span> <span class="token keyword">EMPTY</span><span class="token punctuation">,</span>
ct <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">PATH</span> <span class="token string">'$.c'</span> <span class="token keyword">DEFAULT</span> <span class="token string">'3'</span> <span class="token keyword">ON</span> <span class="token keyword">EMPTY</span>
<span class="token punctuation">)</span>
<span class="token punctuation">)</span> <span class="token keyword">AS</span> tt
<span class="token keyword">ON</span> m<span class="token punctuation">.</span>c1 <span class="token operator">></span> tt<span class="token punctuation">.</span><span class="token keyword">at</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Attempting to use the
<code class="literal">
LATERAL
</code>
keyword with this
query raises
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_parse_error" target="_top">
<code class="literal">
ER_PARSE_ERROR
</code>
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-performance-ro-txn.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="innodb-performance-ro-txn">
</a>
10.5.3 Optimizing InnoDB Read-Only Transactions
</h3>
</div>
</div>
</div>
<p>
<code class="literal">
InnoDB
</code>
can avoid the overhead associated with
setting up the
<a class="link" href="glossary.html#glos_transaction_id" title="transaction ID">
transaction
ID
</a>
(
<code class="literal">
TRX_ID
</code>
field) for transactions
that are known to be read-only. A transaction ID is only needed
for a
<a class="link" href="glossary.html#glos_transaction" title="transaction">
transaction
</a>
that
might perform write operations or
<a class="link" href="glossary.html#glos_locking_read" title="locking read">
locking reads
</a>
such as
<code class="literal">
SELECT ... FOR UPDATE
</code>
. Eliminating
unnecessary transaction IDs reduces the size of internal data
structures that are consulted each time a query or data change
statement constructs a
<a class="link" href="glossary.html#glos_read_view" title="read view">
read
view
</a>
.
</p>
<p>
<code class="literal">
InnoDB
</code>
detects read-only transactions when:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The transaction is started with the
<a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
<code class="literal">
START TRANSACTION
READ ONLY
</code>
</a>
statement. In this case, attempting to
make changes to the database (for
<code class="literal">
InnoDB
</code>
,
<code class="literal">
MyISAM
</code>
, or other types of tables) causes
an error, and the transaction continues in read-only state:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-none"><div class="docs-select-all right" id="sa37476308"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">ERROR 1792 (25006): Cannot execute statement in a READ ONLY transaction.</code></pre>
</div>
<p>
You can still make changes to session-specific temporary
tables in a read-only transaction, or issue locking queries
for them, because those changes and locks are not visible to
any other transaction.
</p>
</li>
<li class="listitem">
<p>
The
<a class="link" href="server-system-variables.html#sysvar_autocommit">
<code class="literal">
autocommit
</code>
</a>
setting is
turned on, so that the transaction is guaranteed to be a
single statement, and the single statement making up the
transaction is a
<span class="quote">
“
<span class="quote">
non-locking
</span>
”
</span>
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statement. That is, a
<code class="literal">
SELECT
</code>
that does not use a
<code class="literal">
FOR
UPDATE
</code>
or
<code class="literal">
LOCK IN SHARED MODE
</code>
clause.
</p>
</li>
<li class="listitem">
<p>
The transaction is started without the
<code class="literal">
READ
ONLY
</code>
option, but no updates or statements that
explicitly lock rows have been executed yet. Until updates
or explicit locks are required, a transaction stays in
read-only mode.
</p>
</li>
</ul>
</div>
<p>
Thus, for a read-intensive application such as a report
generator, you can tune a sequence of
<code class="literal">
InnoDB
</code>
queries by grouping them inside
<a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
<code class="literal">
START TRANSACTION READ
ONLY
</code>
</a>
and
<a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
<code class="literal">
COMMIT
</code>
</a>
, or by
turning on the
<a class="link" href="server-system-variables.html#sysvar_autocommit">
<code class="literal">
autocommit
</code>
</a>
setting before running the
<code class="literal">
SELECT
</code>
statements,
or simply by avoiding any data change statements interspersed
with the queries.
</p>
<p>
For information about
<a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
<code class="literal">
START
TRANSACTION
</code>
</a>
and
<a class="link" href="server-system-variables.html#sysvar_autocommit">
<code class="literal">
autocommit
</code>
</a>
, see
<a class="xref" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
Section 15.3.1, “START TRANSACTION, COMMIT, and ROLLBACK Statements”
</a>
.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Transactions that qualify as auto-commit, non-locking, and
read-only (AC-NL-RO) are kept out of certain internal
<code class="literal">
InnoDB
</code>
data structures and are therefore
not listed in
<a class="link" href="show-engine.html" title="15.7.7.16 SHOW ENGINE Statement">
<code class="literal">
SHOW ENGINE
INNODB STATUS
</code>
</a>
output.
</p>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/information-schema-files-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="information-schema-files-table">
</a>
28.3.15 The INFORMATION_SCHEMA FILES Table
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045079850704">
</a>
<a class="indexterm" name="idm46045079849200">
</a>
<p>
The
<code class="literal">
FILES
</code>
table provides information about the
files in which MySQL tablespace data is stored.
</p>
<p>
The
<code class="literal">
FILES
</code>
table provides information about
<code class="literal">
InnoDB
</code>
data files. In NDB Cluster, this table
also provides information about the files in which NDB Cluster
Disk Data tables are stored. For additional information specific
to
<code class="literal">
InnoDB
</code>
, see
<a class="xref" href="information-schema-files-table.html#files-table-innodb-notes" title="InnoDB Notes">
InnoDB Notes
</a>
, later in this section;
for additional information specific to NDB Cluster, see
<a class="xref" href="information-schema-files-table.html#files-table-ndb-notes" title="NDB Notes">
NDB Notes
</a>
.
</p>
<p>
The
<code class="literal">
FILES
</code>
table has these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
FILE_ID
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: The tablespace ID, also
referred to as the
<code class="literal">
space_id
</code>
or
<code class="literal">
fil_space_t::id
</code>
.
</p>
<p>
For
<code class="literal">
NDB
</code>
: A file identifier.
<code class="literal">
FILE_ID
</code>
column values are auto-generated.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
FILE_NAME
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: The name of the data file.
File-per-table and general tablespaces have an
<code class="filename">
.ibd
</code>
file name extension. Undo
tablespaces are prefixed by
<code class="literal">
undo
</code>
. The
system tablespace is prefixed by
<code class="literal">
ibdata
</code>
.
The global temporary tablespace is prefixed by
<code class="literal">
ibtmp
</code>
. The file name includes the file
path, which may be relative to the MySQL data directory (the
value of the
<a class="link" href="server-system-variables.html#sysvar_datadir">
<code class="literal">
datadir
</code>
</a>
system
variable).
</p>
<p>
For
<code class="literal">
NDB
</code>
: The name of an undo log file
created by
<a class="link" href="create-logfile-group.html" title="15.1.16 CREATE LOGFILE GROUP Statement">
<code class="literal">
CREATE LOGFILE GROUP
</code>
</a>
or
<a class="link" href="alter-logfile-group.html" title="15.1.6 ALTER LOGFILE GROUP Statement">
<code class="literal">
ALTER LOGFILE GROUP
</code>
</a>
, or of a
data file created by
<a class="link" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
<code class="literal">
CREATE
TABLESPACE
</code>
</a>
or
<a class="link" href="alter-tablespace.html" title="15.1.10 ALTER TABLESPACE Statement">
<code class="literal">
ALTER
TABLESPACE
</code>
</a>
. In NDB 8.4, the file name
is shown with a relative path; for an undo log file, this path
is relative to the directory
<code class="filename">
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-datadir">
<code class="literal">
DataDir
</code>
</a>
/ndb_
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-nodeid">
<code class="literal">
NodeId
</code>
</a>
_fs/LG
</code>
;
for a data file, it is relative to the directory
<code class="filename">
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-datadir">
<code class="literal">
DataDir
</code>
</a>
/ndb_
<a class="link" href="mysql-cluster-ndbd-definition.html#ndbparam-ndbd-nodeid">
<code class="literal">
NodeId
</code>
</a>
_fs/TS
</code>
.
This means, for example, that the name of a data file created
with
<code class="literal">
ALTER TABLESPACE ts ADD DATAFILE 'data_2.dat'
INITIAL SIZE 256M
</code>
is shown as
<code class="literal">
./data_2.dat
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
FILE_TYPE
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: The tablespace file type. There
are three possible file types for
<code class="literal">
InnoDB
</code>
files.
<code class="literal">
TABLESPACE
</code>
is the file type for any
system, general, or file-per-table tablespace file that holds
tables, indexes, or other forms of user data.
<code class="literal">
TEMPORARY
</code>
is the file type for temporary
tablespaces.
<code class="literal">
UNDO LOG
</code>
is the file type for
undo tablespaces, which hold undo records.
</p>
<p>
For
<code class="literal">
NDB
</code>
: One of the values
<code class="literal">
UNDO
LOG
</code>
or
<code class="literal">
DATAFILE
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TABLESPACE_NAME
</code>
</p>
<p>
The name of the tablespace with which the file is associated.
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: General tablespace names are as
specified when created. File-per-table tablespace names are
shown in the following format:
<code class="literal">
<em class="replaceable">
<code>
schema_name
</code>
</em>
/
<em class="replaceable">
<code>
table_name
</code>
</em>
</code>
.
The
<code class="literal">
InnoDB
</code>
system tablespace name is
<code class="literal">
innodb_system
</code>
. The global temporary
tablespace name is
<code class="literal">
innodb_temporary
</code>
.
Default undo tablespace names are
<code class="literal">
innodb_undo_001
</code>
and
<code class="literal">
innodb_undo_002
</code>
. User-created undo
tablespace names are as specified when created.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TABLE_CATALOG
</code>
</p>
<p>
This value is always empty.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TABLE_SCHEMA
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TABLE_NAME
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
LOGFILE_GROUP_NAME
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: This is always
<code class="literal">
NULL
</code>
.
</p>
<p>
For
<code class="literal">
NDB
</code>
: The name of the log file group to
which the log file or data file belongs.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
LOGFILE_GROUP_NUMBER
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: This is always
<code class="literal">
NULL
</code>
.
</p>
<p>
For
<code class="literal">
NDB
</code>
: For a Disk Data undo log file, the
auto-generated ID number of the log file group to which the
log file belongs. This is the same as the value shown for the
<code class="literal">
id
</code>
column in the
<a class="link" href="mysql-cluster-ndbinfo-dict-obj-info.html" title="25.6.17.25 The ndbinfo dict_obj_info Table">
<code class="literal">
ndbinfo.dict_obj_info
</code>
</a>
table
and the
<code class="literal">
log_id
</code>
column in the
<a class="link" href="mysql-cluster-ndbinfo-logspaces.html" title="25.6.17.44 The ndbinfo logspaces Table">
<code class="literal">
ndbinfo.logspaces
</code>
</a>
and
<a class="link" href="mysql-cluster-ndbinfo-logspaces.html" title="25.6.17.44 The ndbinfo logspaces Table">
<code class="literal">
ndbinfo.logspaces
</code>
</a>
tables for
this undo log file.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ENGINE
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: This value is always
<code class="literal">
InnoDB
</code>
.
</p>
<p>
For
<code class="literal">
NDB
</code>
: This value is always
<code class="literal">
ndbcluster
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
FULLTEXT_KEYS
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
DELETED_ROWS
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
UPDATE_COUNT
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
FREE_EXTENTS
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: The number of fully free
extents in the current data file.
</p>
<p>
For
<code class="literal">
NDB
</code>
: The number of extents which have
not yet been used by the file.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TOTAL_EXTENTS
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: The number of full extents used
in the current data file. Any partial extent at the end of the
file is not counted.
</p>
<p>
For
<code class="literal">
NDB
</code>
: The total number of extents
allocated to the file.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
EXTENT_SIZE
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: Extent size is 1048576 (1MB)
for files with a 4KB, 8KB, or 16KB page size. Extent size is
2097152 bytes (2MB) for files with a 32KB page size, and
4194304 (4MB) for files with a 64KB page size.
<a class="link" href="information-schema-files-table.html" title="28.3.15 The INFORMATION_SCHEMA FILES Table">
<code class="literal">
FILES
</code>
</a>
does not report
<code class="literal">
InnoDB
</code>
page size. Page size is defined by
the
<a class="link" href="innodb-parameters.html#sysvar_innodb_page_size">
<code class="literal">
innodb_page_size
</code>
</a>
system
variable. Extent size information can also be retrieved from
the
<a class="link" href="information-schema-innodb-tablespaces-table.html" title="28.4.24 The INFORMATION_SCHEMA INNODB_TABLESPACES Table">
<code class="literal">
INNODB_TABLESPACES
</code>
</a>
table
where
<code class="literal">
FILES.FILE_ID =
INNODB_TABLESPACES.SPACE
</code>
.
</p>
<p>
For
<code class="literal">
NDB
</code>
: The size of an extent for the file
in bytes.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
INITIAL_SIZE
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: The initial size of the file in
bytes.
</p>
<p>
For
<code class="literal">
NDB
</code>
: The size of the file in bytes.
This is the same value that was used in the
<code class="literal">
INITIAL_SIZE
</code>
clause of the
<a class="link" href="create-logfile-group.html" title="15.1.16 CREATE LOGFILE GROUP Statement">
<code class="literal">
CREATE LOGFILE GROUP
</code>
</a>
,
<a class="link" href="alter-logfile-group.html" title="15.1.6 ALTER LOGFILE GROUP Statement">
<code class="literal">
ALTER LOGFILE GROUP
</code>
</a>
,
<a class="link" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
<code class="literal">
CREATE TABLESPACE
</code>
</a>
, or
<a class="link" href="alter-tablespace.html" title="15.1.10 ALTER TABLESPACE Statement">
<code class="literal">
ALTER TABLESPACE
</code>
</a>
statement used
to create the file.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MAXIMUM_SIZE
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: The maximum number of bytes
permitted in the file. The value is
<code class="literal">
NULL
</code>
for all data files except for predefined system tablespace
data files. Maximum system tablespace file size is defined by
<a class="link" href="innodb-parameters.html#sysvar_innodb_data_file_path">
<code class="literal">
innodb_data_file_path
</code>
</a>
.
Maximum global temporary tablespace file size is defined by
<a class="link" href="innodb-parameters.html#sysvar_innodb_temp_data_file_path">
<code class="literal">
innodb_temp_data_file_path
</code>
</a>
. A
<code class="literal">
NULL
</code>
value for a predefined system
tablespace data file indicates that a file size limit was not
defined explicitly.
</p>
<p>
For
<code class="literal">
NDB
</code>
: This value is always the same as
the
<code class="literal">
INITIAL_SIZE
</code>
value.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
AUTOEXTEND_SIZE
</code>
</p>
<p>
The auto-extend size of the tablespace. For
<code class="literal">
NDB
</code>
,
<code class="literal">
AUTOEXTEND_SIZE
</code>
is
always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CREATION_TIME
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
LAST_UPDATE_TIME
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
LAST_ACCESS_TIME
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
RECOVER_TIME
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TRANSACTION_COUNTER
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
VERSION
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: This is always
<code class="literal">
NULL
</code>
.
</p>
<p>
For
<code class="literal">
NDB
</code>
: The version number of the file.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ROW_FORMAT
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: This is always
<code class="literal">
NULL
</code>
.
</p>
<p>
For
<code class="literal">
NDB
</code>
: One of
<code class="literal">
FIXED
</code>
or
<code class="literal">
DYNAMIC
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TABLE_ROWS
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
AVG_ROW_LENGTH
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
DATA_LENGTH
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
MAX_DATA_LENGTH
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
INDEX_LENGTH
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
DATA_FREE
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: The total amount of free space
(in bytes) for the entire tablespace. Predefined system
tablespaces, which include the system tablespace and temporary
table tablespaces, may have one or more data files.
</p>
<p>
For
<code class="literal">
NDB
</code>
: This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CREATE_TIME
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
UPDATE_TIME
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CHECK_TIME
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
CHECKSUM
</code>
</p>
<p>
This is always
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
STATUS
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: This value is
<code class="literal">
NORMAL
</code>
by default.
<code class="literal">
InnoDB
</code>
file-per-table tablespaces may
report
<code class="literal">
IMPORTING
</code>
, which indicates that the
tablespace is not yet available.
</p>
<p>
For
<code class="literal">
NDB
</code>
: For NDB Cluster Disk Data files,
this value is always
<code class="literal">
NORMAL
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
EXTRA
</code>
</p>
<p>
For
<code class="literal">
InnoDB
</code>
: This is always
<code class="literal">
NULL
</code>
.
</p>
<p>
For
<code class="literal">
NDB
</code>
: For undo log files, this column
shows the undo log buffer size; for data files, it is always
<span class="emphasis">
<em>
NULL
</em>
</span>
. A more detailed explanation is
provided in the next few paragraphs.
</p>
<p>
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
stores a copy of each data
file and each undo log file on each data node in the cluster.
The
<code class="literal">
FILES
</code>
table contains one row for each
such file. Suppose that you run the following two statements
on an NDB Cluster with four data nodes:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa59001128"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">LOGFILE</span> <span class="token keyword">GROUP</span> mygroup
<span class="token keyword">ADD</span> <span class="token keyword">UNDOFILE</span> <span class="token string">'new_undo.dat'</span>
<span class="token keyword">INITIAL_SIZE</span> 2G
<span class="token keyword">ENGINE</span> <span class="token keyword">NDBCLUSTER</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLESPACE</span> myts
<span class="token keyword">ADD</span> <span class="token keyword">DATAFILE</span> <span class="token string">'data_1.dat'</span>
<span class="token keyword">USE</span> <span class="token keyword">LOGFILE</span> <span class="token keyword">GROUP</span> mygroup
<span class="token keyword">INITIAL_SIZE</span> 256M
<span class="token keyword">ENGINE</span> <span class="token keyword">NDBCLUSTER</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
After running these two statements successfully, you should
see a result similar to the one shown here for this query
against the
<a class="link" href="information-schema-files-table.html" title="28.3.15 The INFORMATION_SCHEMA FILES Table">
<code class="literal">
FILES
</code>
</a>
table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa49308716"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> LOGFILE_GROUP_NAME<span class="token punctuation">,</span> FILE_TYPE<span class="token punctuation">,</span> EXTRA
<span class="token prompt"> -></span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>FILES
<span class="token prompt"> -></span> <span class="token keyword">WHERE</span> <span class="token keyword">ENGINE</span> <span class="token operator">=</span> <span class="token string">'ndbcluster'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> LOGFILE_GROUP_NAME <span class="token punctuation">|</span> FILE_TYPE <span class="token punctuation">|</span> EXTRA <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> mygroup <span class="token punctuation">|</span> UNDO LOG <span class="token punctuation">|</span> UNDO_BUFFER_SIZE=8388608 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> mygroup <span class="token punctuation">|</span> DATAFILE <span class="token punctuation">|</span> NULL <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="files-table-notes">
</a>
Notes
</h4>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="link" href="information-schema-files-table.html" title="28.3.15 The INFORMATION_SCHEMA FILES Table">
<code class="literal">
FILES
</code>
</a>
is a nonstandard
<code class="literal">
INFORMATION_SCHEMA
</code>
table.
</p>
</li>
<li class="listitem">
<p>
You must have the
<a class="link" href="privileges-provided.html#priv_process">
<code class="literal">
PROCESS
</code>
</a>
privilege to query this table.
</p>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="files-table-innodb-notes">
</a>
InnoDB Notes
</h4>
</div>
</div>
</div>
<p>
The following notes apply to
<code class="literal">
InnoDB
</code>
data
files.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Information reported by
<code class="literal">
FILES
</code>
is obtained
from the
<code class="literal">
InnoDB
</code>
in-memory cache for open
files, whereas
<a class="link" href="information-schema-innodb-datafiles-table.html" title="28.4.10 The INFORMATION_SCHEMA INNODB_DATAFILES Table">
<code class="literal">
INNODB_DATAFILES
</code>
</a>
gets its data from the
<code class="literal">
InnoDB
</code>
<code class="literal">
SYS_DATAFILES
</code>
internal data dictionary
table.
</p>
</li>
<li class="listitem">
<p>
The information provided by
<code class="literal">
FILES
</code>
includes global temporary tablespace information which is
not available in the
<code class="literal">
InnoDB
</code>
<code class="literal">
SYS_DATAFILES
</code>
internal data dictionary
table, and is therefore not included in
<a class="link" href="information-schema-innodb-datafiles-table.html" title="28.4.10 The INFORMATION_SCHEMA INNODB_DATAFILES Table">
<code class="literal">
INNODB_DATAFILES
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
Undo tablespace information is shown in
<code class="literal">
FILES
</code>
when separate undo tablespaces are
present, as they are by default in MySQL 8.4.
</p>
</li>
<li class="listitem">
<p>
The following query returns all
<code class="literal">
FILES
</code>
table information relating to
<code class="literal">
InnoDB
</code>
tablespaces.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa41197914"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span>
FILE_ID<span class="token punctuation">,</span> FILE_NAME<span class="token punctuation">,</span> FILE_TYPE<span class="token punctuation">,</span> TABLESPACE_NAME<span class="token punctuation">,</span> FREE_EXTENTS<span class="token punctuation">,</span>
TOTAL_EXTENTS<span class="token punctuation">,</span> <span class="token keyword">EXTENT_SIZE</span><span class="token punctuation">,</span> <span class="token keyword">INITIAL_SIZE</span><span class="token punctuation">,</span> MAXIMUM_SIZE<span class="token punctuation">,</span>
<span class="token keyword">AUTOEXTEND_SIZE</span><span class="token punctuation">,</span> DATA_FREE<span class="token punctuation">,</span> <span class="token keyword">STATUS</span>
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>FILES
<span class="token keyword">WHERE</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span><span class="token string">'InnoDB'</span>\G</code></pre>
</div>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h4 class="title">
<a name="files-table-ndb-notes">
</a>
NDB Notes
</h4>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
The
<code class="literal">
FILES
</code>
table provides information
about Disk Data
<span class="emphasis">
<em>
files
</em>
</span>
only; you cannot
use it for determining disk space allocation or availability
for individual
<code class="literal">
NDB
</code>
tables. However, it is
possible to see how much space is allocated for each
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
table having data stored on
disk—as well as how much remains available for storage
of data on disk for that table—using
<a class="link" href="mysql-cluster-programs-ndb-desc.html" title="25.5.9 ndb_desc — Describe NDB Tables">
<span class="command">
<strong>
ndb_desc
</strong>
</span>
</a>
.
</p>
</li>
<li class="listitem">
<p>
Much of the information contained in the
<code class="literal">
FILES
</code>
table can also be found in the
<code class="literal">
ndbinfo
</code>
<a class="link" href="mysql-cluster-ndbinfo-files.html" title="25.6.17.36 The ndbinfo files Table">
<code class="literal">
files
</code>
</a>
table.
</p>
</li>
<li class="listitem">
<p>
The
<code class="literal">
CREATION_TIME
</code>
,
<code class="literal">
LAST_UPDATE_TIME
</code>
, and
<code class="literal">
LAST_ACCESSED
</code>
values are as reported by
the operating system, and are not supplied by the
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
storage engine. Where no
value is provided by the operating system, these columns
display
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
The difference between the
<code class="literal">
TOTAL EXTENTS
</code>
and
<code class="literal">
FREE_EXTENTS
</code>
columns is the number of
extents currently in use by the file:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa70174357"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> TOTAL_EXTENTS <span class="token operator">-</span> FREE_EXTENTS <span class="token keyword">AS</span> extents_used
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>FILES
<span class="token keyword">WHERE</span> FILE_NAME <span class="token operator">=</span> <span class="token string">'./myfile.dat'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To approximate the amount of disk space in use by the file,
multiply that difference by the value of the
<code class="literal">
EXTENT_SIZE
</code>
column, which gives the size
of an extent for the file in bytes:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa80249705"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token punctuation">(</span>TOTAL_EXTENTS <span class="token operator">-</span> FREE_EXTENTS<span class="token punctuation">)</span> <span class="token operator">*</span> <span class="token keyword">EXTENT_SIZE</span> <span class="token keyword">AS</span> bytes_used
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>FILES
<span class="token keyword">WHERE</span> FILE_NAME <span class="token operator">=</span> <span class="token string">'./myfile.dat'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Similarly, you can estimate the amount of space that remains
available in a given file by multiplying
<code class="literal">
FREE_EXTENTS
</code>
by
<code class="literal">
EXTENT_SIZE
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa6661385"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> FREE_EXTENTS <span class="token operator">*</span> <span class="token keyword">EXTENT_SIZE</span> <span class="token keyword">AS</span> bytes_free
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>FILES
<span class="token keyword">WHERE</span> FILE_NAME <span class="token operator">=</span> <span class="token string">'./myfile.dat'</span><span class="token punctuation">;</span></code></pre>
</div>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
The byte values produced by the preceding queries are
approximations only, and their precision is inversely
proportional to the value of
<code class="literal">
EXTENT_SIZE
</code>
. That is, the larger
<code class="literal">
EXTENT_SIZE
</code>
becomes, the less accurate
the approximations are.
</p>
</div>
<p>
It is also important to remember that once an extent is
used, it cannot be freed again without dropping the data
file of which it is a part. This means that deletes from a
Disk Data table do
<span class="emphasis">
<em>
not
</em>
</span>
release disk
space.
</p>
<p>
The extent size can be set in a
<a class="link" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
<code class="literal">
CREATE
TABLESPACE
</code>
</a>
statement. For more information, see
<a class="xref" href="create-tablespace.html" title="15.1.21 CREATE TABLESPACE Statement">
Section 15.1.21, “CREATE TABLESPACE Statement”
</a>
.
</p>
</li>
<li class="listitem">
<p>
You can obtain information about Disk Data tablespaces using
the
<a class="link" href="mysql-cluster-programs-ndb-desc.html" title="25.5.9 ndb_desc — Describe NDB Tables">
<span class="command">
<strong>
ndb_desc
</strong>
</span>
</a>
utility. For more
information, see
<a class="xref" href="mysql-cluster-disk-data-objects.html" title="25.6.11.1 NDB Cluster Disk Data Objects">
Section 25.6.11.1, “NDB Cluster Disk Data Objects”
</a>
, as well
as the description of
<a class="link" href="mysql-cluster-programs-ndb-desc.html" title="25.5.9 ndb_desc — Describe NDB Tables">
<span class="command">
<strong>
ndb_desc
</strong>
</span>
</a>
.
</p>
</li>
<li class="listitem">
<p>
For additional information, and examples of creating,
dropping, and obtaining information about NDB Cluster Disk
Data objects, see
<a class="xref" href="mysql-cluster-disk-data.html" title="25.6.11 NDB Cluster Disk Data Tables">
Section 25.6.11, “NDB Cluster Disk Data Tables”
</a>
.
</p>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/set-names.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="set-names">
</a>
15.7.6.3 SET NAMES Statement
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045171340096">
</a>
<a class="indexterm" name="idm46045171339024">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44621320"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">NAMES</span> {<span class="token string">'<em class="replaceable">charset_name</em>'</span>
<span class="token punctuation">[</span><span class="token keyword">COLLATE</span> <span class="token string">'<em class="replaceable">collation_name</em>'</span><span class="token punctuation">]</span> <span class="token operator">|</span> <span class="token keyword">DEFAULT</span>}</code></pre>
</div>
<p>
This statement sets the three session system variables
<a class="link" href="server-system-variables.html#sysvar_character_set_client">
<code class="literal">
character_set_client
</code>
</a>
,
<a class="link" href="server-system-variables.html#sysvar_character_set_connection">
<code class="literal">
character_set_connection
</code>
</a>
, and
<a class="link" href="server-system-variables.html#sysvar_character_set_results">
<code class="literal">
character_set_results
</code>
</a>
to the
given character set. Setting
<a class="link" href="server-system-variables.html#sysvar_character_set_connection">
<code class="literal">
character_set_connection
</code>
</a>
to
<code class="literal">
charset_name
</code>
also sets
<a class="link" href="server-system-variables.html#sysvar_collation_connection">
<code class="literal">
collation_connection
</code>
</a>
to the
default collation for
<code class="literal">
charset_name
</code>
. See
<a class="xref" href="charset-connection.html" title="12.4 Connection Character Sets and Collations">
Section 12.4, “Connection Character Sets and Collations”
</a>
.
</p>
<p>
The optional
<code class="literal">
COLLATE
</code>
clause may be used to
specify a collation explicitly. If given, the collation must one
of the permitted collations for
<em class="replaceable">
<code>
charset_name
</code>
</em>
.
</p>
<p>
<em class="replaceable">
<code>
charset_name
</code>
</em>
and
<em class="replaceable">
<code>
collation_name
</code>
</em>
may be quoted or
unquoted.
</p>
<p>
The default mapping can be restored by using a value of
<code class="literal">
DEFAULT
</code>
. The default depends on the server
configuration.
</p>
<p>
Some character sets cannot be used as the client character set.
Attempting to use them with
<a class="link" href="set-names.html" title="15.7.6.3 SET NAMES Statement">
<code class="literal">
SET
NAMES
</code>
</a>
produces an error. See
<a class="xref" href="charset-connection.html#charset-connection-impermissible-client-charset" title="Impermissible Client Character Sets">
Impermissible Client Character Sets
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/clone-plugin-failure-handling.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="clone-plugin-failure-handling">
</a>
7.6.7.9 Remote Cloning Operation Failure Handling
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045255340368">
</a>
<p>
This section describes failure handing at different stages of a
cloning operation.
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Prerequisites are checked (see
<a class="xref" href="clone-plugin-remote.html#clone-remote-prerequisites" title="Remote Cloning Prerequisites">
Remote Cloning Prerequisites
</a>
).
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If a failure occurs during the prerequisite check, the
<a class="link" href="clone.html" title="15.7.5 CLONE Statement">
<code class="literal">
CLONE
INSTANCE
</code>
</a>
operation reports an error.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Concurrent DDL on the donor is blocked only if the
<a class="link" href="clone-plugin-options-variables.html#sysvar_clone_block_ddl">
<code class="literal">
clone_block_ddl
</code>
</a>
variable is
set to
<code class="literal">
ON
</code>
(the default setting is
<code class="literal">
OFF
</code>
). See
<a class="xref" href="clone-plugin-concurrent-ddl.html" title="7.6.7.4 Cloning and Concurrent DDL">
Section 7.6.7.4, “Cloning and Concurrent DDL”
</a>
.
</p>
<p>
If the cloning operation is unable to obtain a DDL lock
within the time limit specified by the
<a class="link" href="clone-plugin-options-variables.html#sysvar_clone_ddl_timeout">
<code class="literal">
clone_ddl_timeout
</code>
</a>
variable,
an error is reported.
</p>
</li>
<li class="listitem">
<p>
User-created data (schemas, tables, tablespaces) and binary
logs on the recipient are removed before data is cloned to
the recipient data directory.
</p>
<p>
When user-created data and binary logs are removed from the
recipient data directory during a remote cloning operation,
the data is not saved and may be lost if a failure occurs.
If the data is of importance, a backup should be taken
before initiating a remote cloning operation.
</p>
<p>
For informational purposes, warnings are printed to the
server error log to specify when data removal starts and
finishes:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa56265458"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token punctuation">[</span>Warning<span class="token punctuation">]</span> <span class="token punctuation">[</span>MY-013453<span class="token punctuation">]</span> <span class="token punctuation">[</span>InnoDB<span class="token punctuation">]</span> Clone removing all user data for provisioning<span class="token punctuation">:</span>
Started<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token punctuation">[</span>Warning<span class="token punctuation">]</span> <span class="token punctuation">[</span>MY-013453<span class="token punctuation">]</span> <span class="token punctuation">[</span>InnoDB<span class="token punctuation">]</span> Clone removing all user data for provisioning<span class="token punctuation">:</span>
Finished</code></pre>
</div>
<p>
If a failure occurs while removing data, the recipient may
be left with a partial set of schemas, tables, and
tablespaces that existed before the cloning operation. Any
time during the execution of a cloning operation or after a
failure, the server is always in a consistent state.
</p>
</li>
<li class="listitem">
<p>
Data is cloned from the donor. User-created data, dictionary
metadata, and other system data are cloned.
</p>
<p>
If a failure occurs while cloning data, the cloning
operation is rolled back and all cloned data removed. At
this stage, the previously existing user-created data and
binary logs on the recipient have also been removed.
</p>
<p>
Should this scenario occur, you can either rectify the cause
of the failure and re-execute the cloning operation, or
forgo the cloning operation and restore the recipient data
from a backup taken before the cloning operation.
</p>
</li>
<li class="listitem">
<p>
The server is restarted automatically (applies to remote
cloning operations that do not clone to a named directory).
During startup, typical server startup tasks are performed.
</p>
<p>
If the automatic server restart fails, you can restart the
server manually to complete the cloning operation.
</p>
</li>
</ol>
</div>
<p>
If a network error occurs during a cloning operation, the
operation resumes if the error is resolved within the time
specified by the
<a class="link" href="clone-plugin-options-variables.html#sysvar_clone_donor_timeout_after_network_failure">
<code class="literal">
clone_donor_timeout_after_network_failure
</code>
</a>
variable defined on the donor instance. The
<a class="link" href="clone-plugin-options-variables.html#sysvar_clone_donor_timeout_after_network_failure">
<code class="literal">
clone_donor_timeout_after_network_failure
</code>
</a>
default setting is 5 minutes but a range of 0 to 30 minutes is
supported. If the operation does not resume within the allotted
time, it aborts and returns an error, and the donor drops the
snapshot. A setting of zero causes the donor to drop the
snapshot immediately when a network error occurs. Configuring a
longer timeout allows more time for resolving network issues but
also increases the size of the delta on the donor instance,
which increases clone recovery time as well as replication lag
in cases where the clone is intended as a replica or replication
group member.
</p>
<p>
The Clone idle timeout is set to the default
<a class="link" href="server-system-variables.html#sysvar_wait_timeout">
<code class="literal">
wait_timeout
</code>
</a>
setting, which is
28800 seconds (8 hours).
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/outer-join-simplification.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="outer-join-simplification">
</a>
10.2.1.10 Outer Join Simplification
</h4>
</div>
</div>
</div>
<p>
Table expressions in the
<code class="literal">
FROM
</code>
clause of a
query are simplified in many cases.
</p>
<p>
At the parser stage, queries with right outer join operations
are converted to equivalent queries containing only left join
operations. In the general case, the conversion is performed
such that this right join:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa71497724"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token punctuation">(</span>T1<span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span> <span class="token keyword">RIGHT</span> <span class="token keyword">JOIN</span> <span class="token punctuation">(</span>T2<span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span> <span class="token keyword">ON</span> P<span class="token punctuation">(</span>T1<span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">,</span> T2<span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
Becomes this equivalent left join:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa75153091"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token punctuation">(</span>T2<span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span> <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> <span class="token punctuation">(</span>T1<span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span> <span class="token keyword">ON</span> P<span class="token punctuation">(</span>T1<span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">,</span> T2<span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
All inner join expressions of the form
<code class="literal">
T1 INNER JOIN
T2 ON P(T1,T2)
</code>
are replaced by the list
<code class="literal">
T1,T2
</code>
,
<code class="literal">
P(T1,T2)
</code>
being
joined as a conjunct to the
<code class="literal">
WHERE
</code>
condition
(or to the join condition of the embedding join, if there is
any).
</p>
<p>
When the optimizer evaluates plans for outer join operations,
it takes into consideration only plans where, for each such
operation, the outer tables are accessed before the inner
tables. The optimizer choices are limited because only such
plans enable outer joins to be executed using the nested-loop
algorithm.
</p>
<p>
Consider a query of this form, where
<code class="literal">
R(T2)
</code>
greatly narrows the number of matching rows from table
<code class="literal">
T2
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa69088826"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> T1 <span class="token keyword">FROM</span> T1
<span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> T2 <span class="token keyword">ON</span> P1<span class="token punctuation">(</span>T1<span class="token punctuation">,</span>T2<span class="token punctuation">)</span>
<span class="token keyword">WHERE</span> P<span class="token punctuation">(</span>T1<span class="token punctuation">,</span>T2<span class="token punctuation">)</span> <span class="token operator">AND</span> R<span class="token punctuation">(</span>T2<span class="token punctuation">)</span></code></pre>
</div>
<p>
If the query is executed as written, the optimizer has no
choice but to access the less-restricted table
<code class="literal">
T1
</code>
before the more-restricted table
<code class="literal">
T2
</code>
, which may produce a very inefficient
execution plan.
</p>
<p>
Instead, MySQL converts the query to a query with no outer
join operation if the
<code class="literal">
WHERE
</code>
condition is
null-rejected. (That is, it converts the outer join to an
inner join.) A condition is said to be null-rejected for an
outer join operation if it evaluates to
<code class="literal">
FALSE
</code>
or
<code class="literal">
UNKNOWN
</code>
for any
<code class="literal">
NULL
</code>
-complemented row generated for the
operation.
</p>
<a class="indexterm" name="idm46045229367968">
</a>
<a class="indexterm" name="idm46045229366896">
</a>
<p>
Thus, for this outer join:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa40717270"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">T1 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> T2 <span class="token keyword">ON</span> T1<span class="token punctuation">.</span>A<span class="token operator">=</span>T2<span class="token punctuation">.</span>A</code></pre>
</div>
<p>
Conditions such as these are null-rejected because they cannot
be true for any
<code class="literal">
NULL
</code>
-complemented row (with
<code class="literal">
T2
</code>
columns set to
<code class="literal">
NULL
</code>
):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa20929956"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">T2<span class="token punctuation">.</span>B <span class="token operator">IS</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span>
T2<span class="token punctuation">.</span>B <span class="token operator">></span> <span class="token number">3</span>
T2<span class="token punctuation">.</span>C <span class="token operator"><=</span> T1<span class="token punctuation">.</span>C
T2<span class="token punctuation">.</span>B <span class="token operator"><</span> <span class="token number">2</span> <span class="token operator">OR</span> T2<span class="token punctuation">.</span>C <span class="token operator">></span> <span class="token number">1</span></code></pre>
</div>
<p>
Conditions such as these are not null-rejected because they
might be true for a
<code class="literal">
NULL
</code>
-complemented row:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa14993757"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">T2<span class="token punctuation">.</span>B <span class="token operator">IS</span> <span class="token boolean">NULL</span>
T1<span class="token punctuation">.</span>B <span class="token operator"><</span> <span class="token number">3</span> <span class="token operator">OR</span> T2<span class="token punctuation">.</span>B <span class="token operator">IS</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span>
T1<span class="token punctuation">.</span>B <span class="token operator"><</span> <span class="token number">3</span> <span class="token operator">OR</span> T2<span class="token punctuation">.</span>B <span class="token operator">></span> <span class="token number">3</span></code></pre>
</div>
<p>
The general rules for checking whether a condition is
null-rejected for an outer join operation are simple:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
It is of the form
<code class="literal">
A IS NOT NULL
</code>
, where
<code class="literal">
A
</code>
is an attribute of any of the inner
tables
</p>
</li>
<li class="listitem">
<p>
It is a predicate containing a reference to an inner table
that evaluates to
<code class="literal">
UNKNOWN
</code>
when one of
its arguments is
<code class="literal">
NULL
</code>
</p>
</li>
<li class="listitem">
<p>
It is a conjunction containing a null-rejected condition
as a conjunct
</p>
</li>
<li class="listitem">
<p>
It is a disjunction of null-rejected conditions
</p>
</li>
</ul>
</div>
<p>
A condition can be null-rejected for one outer join operation
in a query and not null-rejected for another. In this query,
the
<code class="literal">
WHERE
</code>
condition is null-rejected for
the second outer join operation but is not null-rejected for
the first one:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51634784"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> T1 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> T2 <span class="token keyword">ON</span> T2<span class="token punctuation">.</span>A<span class="token operator">=</span>T1<span class="token punctuation">.</span>A
<span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> T3 <span class="token keyword">ON</span> T3<span class="token punctuation">.</span>B<span class="token operator">=</span>T1<span class="token punctuation">.</span>B
<span class="token keyword">WHERE</span> T3<span class="token punctuation">.</span>C <span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
<p>
If the
<code class="literal">
WHERE
</code>
condition is null-rejected for
an outer join operation in a query, the outer join operation
is replaced by an inner join operation.
</p>
<p>
For example, in the preceding query, the second outer join is
null-rejected and can be replaced by an inner join:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa82962972"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> T1 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> T2 <span class="token keyword">ON</span> T2<span class="token punctuation">.</span>A<span class="token operator">=</span>T1<span class="token punctuation">.</span>A
<span class="token keyword">INNER</span> <span class="token keyword">JOIN</span> T3 <span class="token keyword">ON</span> T3<span class="token punctuation">.</span>B<span class="token operator">=</span>T1<span class="token punctuation">.</span>B
<span class="token keyword">WHERE</span> T3<span class="token punctuation">.</span>C <span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
<p>
For the original query, the optimizer evaluates only plans
compatible with the single table-access order
<code class="literal">
T1,T2,T3
</code>
. For the rewritten query, it
additionally considers the access order
<code class="literal">
T3,T1,T2
</code>
.
</p>
<p>
A conversion of one outer join operation may trigger a
conversion of another. Thus, the query:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa59083841"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> T1 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> T2 <span class="token keyword">ON</span> T2<span class="token punctuation">.</span>A<span class="token operator">=</span>T1<span class="token punctuation">.</span>A
<span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> T3 <span class="token keyword">ON</span> T3<span class="token punctuation">.</span>B<span class="token operator">=</span>T2<span class="token punctuation">.</span>B
<span class="token keyword">WHERE</span> T3<span class="token punctuation">.</span>C <span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
<p>
Is first converted to the query:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa17936104"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> T1 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> T2 <span class="token keyword">ON</span> T2<span class="token punctuation">.</span>A<span class="token operator">=</span>T1<span class="token punctuation">.</span>A
<span class="token keyword">INNER</span> <span class="token keyword">JOIN</span> T3 <span class="token keyword">ON</span> T3<span class="token punctuation">.</span>B<span class="token operator">=</span>T2<span class="token punctuation">.</span>B
<span class="token keyword">WHERE</span> T3<span class="token punctuation">.</span>C <span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
<p>
Which is equivalent to the query:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa60836723"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> <span class="token punctuation">(</span>T1 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> T2 <span class="token keyword">ON</span> T2<span class="token punctuation">.</span>A<span class="token operator">=</span>T1<span class="token punctuation">.</span>A<span class="token punctuation">)</span><span class="token punctuation">,</span> T3
<span class="token keyword">WHERE</span> T3<span class="token punctuation">.</span>C <span class="token operator">></span> <span class="token number">0</span> <span class="token operator">AND</span> T3<span class="token punctuation">.</span>B<span class="token operator">=</span>T2<span class="token punctuation">.</span>B</code></pre>
</div>
<p>
The remaining outer join operation can also be replaced by an
inner join because the condition
<code class="literal">
T3.B=T2.B
</code>
is null-rejected. This results in a query with no outer joins
at all:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa25027061"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> <span class="token punctuation">(</span>T1 <span class="token keyword">INNER</span> <span class="token keyword">JOIN</span> T2 <span class="token keyword">ON</span> T2<span class="token punctuation">.</span>A<span class="token operator">=</span>T1<span class="token punctuation">.</span>A<span class="token punctuation">)</span><span class="token punctuation">,</span> T3
<span class="token keyword">WHERE</span> T3<span class="token punctuation">.</span>C <span class="token operator">></span> <span class="token number">0</span> <span class="token operator">AND</span> T3<span class="token punctuation">.</span>B<span class="token operator">=</span>T2<span class="token punctuation">.</span>B</code></pre>
</div>
<p>
Sometimes the optimizer succeeds in replacing an embedded
outer join operation, but cannot convert the embedding outer
join. The following query:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa37119848"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> T1 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span>
<span class="token punctuation">(</span>T2 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> T3 <span class="token keyword">ON</span> T3<span class="token punctuation">.</span>B<span class="token operator">=</span>T2<span class="token punctuation">.</span>B<span class="token punctuation">)</span>
<span class="token keyword">ON</span> T2<span class="token punctuation">.</span>A<span class="token operator">=</span>T1<span class="token punctuation">.</span>A
<span class="token keyword">WHERE</span> T3<span class="token punctuation">.</span>C <span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
<p>
Is converted to:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa78604685"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> T1 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span>
<span class="token punctuation">(</span>T2 <span class="token keyword">INNER</span> <span class="token keyword">JOIN</span> T3 <span class="token keyword">ON</span> T3<span class="token punctuation">.</span>B<span class="token operator">=</span>T2<span class="token punctuation">.</span>B<span class="token punctuation">)</span>
<span class="token keyword">ON</span> T2<span class="token punctuation">.</span>A<span class="token operator">=</span>T1<span class="token punctuation">.</span>A
<span class="token keyword">WHERE</span> T3<span class="token punctuation">.</span>C <span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
<p>
That can be rewritten only to the form still containing the
embedding outer join operation:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa46473180"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> T1 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span>
<span class="token punctuation">(</span>T2<span class="token punctuation">,</span>T3<span class="token punctuation">)</span>
<span class="token keyword">ON</span> <span class="token punctuation">(</span>T2<span class="token punctuation">.</span>A<span class="token operator">=</span>T1<span class="token punctuation">.</span>A <span class="token operator">AND</span> T3<span class="token punctuation">.</span>B<span class="token operator">=</span>T2<span class="token punctuation">.</span>B<span class="token punctuation">)</span>
<span class="token keyword">WHERE</span> T3<span class="token punctuation">.</span>C <span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
<p>
Any attempt to convert an embedded outer join operation in a
query must take into account the join condition for the
embedding outer join together with the
<code class="literal">
WHERE
</code>
condition. In this query, the
<code class="literal">
WHERE
</code>
condition is not null-rejected for
the embedded outer join, but the join condition of the
embedding outer join
<code class="literal">
T2.A=T1.A AND
T3.C=T1.C
</code>
is null-rejected:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51078108"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> T1 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span>
<span class="token punctuation">(</span>T2 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span> T3 <span class="token keyword">ON</span> T3<span class="token punctuation">.</span>B<span class="token operator">=</span>T2<span class="token punctuation">.</span>B<span class="token punctuation">)</span>
<span class="token keyword">ON</span> T2<span class="token punctuation">.</span>A<span class="token operator">=</span>T1<span class="token punctuation">.</span>A <span class="token operator">AND</span> T3<span class="token punctuation">.</span>C<span class="token operator">=</span>T1<span class="token punctuation">.</span>C
<span class="token keyword">WHERE</span> T3<span class="token punctuation">.</span>D <span class="token operator">></span> <span class="token number">0</span> <span class="token operator">OR</span> T1<span class="token punctuation">.</span>D <span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
<p>
Consequently, the query can be converted to:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa88925804"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> T1 <span class="token keyword">LEFT</span> <span class="token keyword">JOIN</span>
<span class="token punctuation">(</span>T2<span class="token punctuation">,</span> T3<span class="token punctuation">)</span>
<span class="token keyword">ON</span> T2<span class="token punctuation">.</span>A<span class="token operator">=</span>T1<span class="token punctuation">.</span>A <span class="token operator">AND</span> T3<span class="token punctuation">.</span>C<span class="token operator">=</span>T1<span class="token punctuation">.</span>C <span class="token operator">AND</span> T3<span class="token punctuation">.</span>B<span class="token operator">=</span>T2<span class="token punctuation">.</span>B
<span class="token keyword">WHERE</span> T3<span class="token punctuation">.</span>D <span class="token operator">></span> <span class="token number">0</span> <span class="token operator">OR</span> T1<span class="token punctuation">.</span>D <span class="token operator">></span> <span class="token number">0</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-cpustat-1sec.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-ndbinfo-cpustat-1sec">
</a>
25.6.17.21 The ndbinfo cpustat_1sec Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045089881600">
</a>
<p>
The
<code class="literal">
cpustat-1sec
</code>
table provides raw,
per-thread CPU data obtained each second for each thread running
in the
<code class="literal">
NDB
</code>
kernel.
</p>
<p>
Like
<a class="link" href="mysql-cluster-ndbinfo-cpustat-50ms.html" title="25.6.17.20 The ndbinfo cpustat_50ms Table">
<code class="literal">
cpustat_50ms
</code>
</a>
and
<a class="link" href="mysql-cluster-ndbinfo-cpustat-20sec.html" title="25.6.17.22 The ndbinfo cpustat_20sec Table">
<code class="literal">
cpustat_20sec
</code>
</a>
, this table
shows 20 measurement sets per thread, each referencing a period
of the named duration. Thus,
<code class="literal">
cpsustat_1sec
</code>
provides 20 seconds of history.
</p>
<p>
The
<code class="literal">
cpustat_1sec
</code>
table contains the following
columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
node_id
</code>
</p>
<p>
ID of the node where the thread is running
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
thr_no
</code>
</p>
<p>
Thread ID (specific to this node)
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OS_user_time
</code>
</p>
<p>
OS user time
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OS_system_time
</code>
</p>
<p>
OS system time
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
OS_idle_time
</code>
</p>
<p>
OS idle time
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
exec_time
</code>
</p>
<p>
Thread execution time
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
sleep_time
</code>
</p>
<p>
Thread sleep time
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
spin_time
</code>
</p>
<p>
Thread spin time
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
send_time
</code>
</p>
<p>
Thread send time
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
buffer_full_time
</code>
</p>
<p>
Thread buffer full time
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
elapsed_time
</code>
</p>
<p>
Elapsed time
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/replication-multi-source-provision-replica.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="replication-multi-source-provision-replica">
</a>
19.1.5.2 Provisioning a Multi-Source Replica for GTID-Based Replication
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045145289248">
</a>
<p>
If the sources in the multi-source replication topology have
existing data, it can save time to provision the replica with the
relevant data before starting replication. In a multi-source
replication topology, cloning or copying of the data directory
cannot be used to provision the replica with data from all of the
sources, and you might also want to replicate only specific
databases from each source. The best strategy for provisioning
such a replica is therefore to use
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
to
create an appropriate dump file on each source, then use the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client to import the dump file on the
replica.
</p>
<p>
If you are using GTID-based replication, you need to pay attention
to the
<code class="literal">
SET @@GLOBAL.gtid_purged
</code>
statement that
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
places in the dump output. This
statement transfers the GTIDs for the transactions executed on the
source to the replica, and the replica requires this information.
However, for any case more complex than provisioning one new,
empty replica from one source, you need to check what effect the
statement has in the version of MySQL used by the replica, and
handle the statement accordingly. The following guidance
summarizes suitable actions, but for more details, see the
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
documentation.
</p>
<p>
<code class="literal">
SET @@GLOBAL.gtid_purged
</code>
adds the GTID set from
the dump file to the existing
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
set on the replica.
The statement can therefore potentially be left in the dump output
when you replay the dump files on the replica, and the dump files
can be replayed at different times. However, it is important to
note that the value that is included by
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
for the
<code class="literal">
SET
@@GLOBAL.gtid_purged
</code>
statement includes the GTIDs of all
transactions in the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
set on the source, even those that changed suppressed parts of the
database, or other databases on the server that were not included
in a partial dump. If you replay a second or subsequent dump file
on the replica that contains any of the same GTIDs (for example,
another partial dump from the same source, or a dump from another
source that has overlapping transactions), any
<code class="literal">
SET
@@GLOBAL.gtid_purged
</code>
statement in the second dump file
fails, and must therefore be removed from the dump output.
</p>
<p>
As an alternative to removing the
<code class="literal">
SET
@@GLOBAL.gtid_purged
</code>
statement, you caninoke
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
with
<a class="link" href="mysqldump.html#option_mysqldump_set-gtid-purged">
<code class="option">
--set-gtid-purged=COMMENTED
</code>
</a>
to
include the statement encased in SQL comments, so that it is not
performed when you load the dump file. If you are provisioning the
replica with two partial dumps from the same source, and the GTID
set in the second dump is the same as the first (so no new
transactions have been executed on the source in between the
dumps), you can set
<code class="option">
--set-gtid-purged=OFF
</code>
instead
when you export the second dump file, to omit the statement.
</p>
<p>
In the following provisioning example, we assume that the
<code class="literal">
SET @@GLOBAL.gtid_purged
</code>
statement cannot be
left in the dump output, and must be removed from the files and
handled manually. We also assume that there are no wanted
transactions with GTIDs on the replica before provisioning starts.
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
To create dump files for a database named
<code class="literal">
db1
</code>
on
<code class="literal">
source1
</code>
and a
database named
<code class="literal">
db2
</code>
on
<code class="literal">
source2
</code>
, run
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
for
<code class="literal">
source1
</code>
as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa63011546"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqldump <span class="token property">-u<<em class="replaceable">user</em>></span> <span class="token property">-p<<em class="replaceable">password</em>></span> <span class="token property">--single-transaction</span> <span class="token property">--triggers</span> <span class="token property">--routines</span> <span class="token constant">--set-gtid-purged</span><span class="token attr-value"><span class="token punctuation">=</span>ON</span> <span class="token property">--databases</span> db1 > dumpM1<span class="token punctuation">.</span>sql</code></pre>
</div>
<p>
Then run
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
for
<code class="literal">
source2
</code>
as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa39049457"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqldump <span class="token property">-u<<em class="replaceable">user</em>></span> <span class="token property">-p<<em class="replaceable">password</em>></span> <span class="token property">--single-transaction</span> <span class="token property">--triggers</span> <span class="token property">--routines</span> <span class="token constant">--set-gtid-purged</span><span class="token attr-value"><span class="token punctuation">=</span>ON</span> <span class="token property">--databases</span> db2 > dumpM2<span class="token punctuation">.</span>sql</code></pre>
</div>
</li>
<li class="listitem">
<p>
Record the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
value
that
<a class="link" href="mysqldump.html" title="6.5.4 mysqldump — A Database Backup Program">
<span class="command">
<strong>
mysqldump
</strong>
</span>
</a>
added to each of the dump
files. You can extract the value like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa32814308"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">cat dumpM1.sql | grep GTID_PURGED | perl -p0 -e 's#/\*.*?\*/##sg' | cut -f2 -d'=' | cut -f2 -d$'\''
cat dumpM2.sql | grep GTID_PURGED | perl -p0 -e 's#/\*.*?\*/##sg' | cut -f2 -d'=' | cut -f2 -d$'\''</code></pre>
</div>
<p>
The result in each case should be a GTID set, for example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa24941290"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">source1: 2174B383-5441-11E8-B90A-C80AA9429562:1-1029
source2: 224DA167-0C0C-11E8-8442-00059A3C7B00:1-2695</code></pre>
</div>
</li>
<li class="listitem">
<p>
Remove the line from each dump file that contains the
<code class="literal">
SET @@GLOBAL.gtid_purged
</code>
statement. For
example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-simple"><div class="docs-select-all right" id="sa37740470"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">sed '<span class="token operator">/</span>GTID_PURGED<span class="token operator">/</span>d' dumpM1<span class="token punctuation">.</span>sql <span class="token operator">></span> dumpM1_nopurge<span class="token punctuation">.</span>sql
sed '<span class="token operator">/</span>GTID_PURGED<span class="token operator">/</span>d' dumpM2<span class="token punctuation">.</span>sql <span class="token operator">></span> dumpM2_nopurge<span class="token punctuation">.</span>sql</code></pre>
</div>
</li>
<li class="listitem">
<p>
Use the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client to import each edited
dump file into the replica. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-simple"><div class="docs-select-all right" id="sa26763012"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">mysql <span class="token operator">-</span>u<span class="token operator"><</span><em class="replaceable">user</em><span class="token operator">></span> <span class="token operator">-</span>p<span class="token operator"><</span><em class="replaceable">password</em><span class="token operator">></span> <span class="token operator"><</span> dumpM1_nopurge<span class="token punctuation">.</span>sql
mysql <span class="token operator">-</span>u<span class="token operator"><</span><em class="replaceable">user</em><span class="token operator">></span> <span class="token operator">-</span>p<span class="token operator"><</span><em class="replaceable">password</em><span class="token operator">></span> <span class="token operator"><</span> dumpM2_nopurge<span class="token punctuation">.</span>sql</code></pre>
</div>
</li>
<li class="listitem">
<p>
On the replica, issue
<a class="link" href="reset-binary-logs-and-gtids.html" title="15.4.1.2 RESET BINARY LOGS AND GTIDS Statement">
<code class="literal">
RESET BINARY LOGS
AND GTIDS
</code>
</a>
to clear the GTID execution history
(assuming, as explained above, that all the dump files have
been imported and that there are no wanted transactions with
GTIDs on the replica). Then issue a
<code class="literal">
SET
@@GLOBAL.gtid_purged
</code>
statement to set the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
value to the
union of all the GTID sets from all the dump files, as you
recorded in Step 2. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa95261942"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">RESET</span> <span class="token datatype">BINARY</span> <span class="token keyword">LOGS</span> <span class="token operator">AND</span> GTIDS<span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@@GLOBAL.gtid_purged</span> <span class="token operator">=</span> <span class="token string">"2174B383-5441-11E8-B90A-C80AA9429562:1-1029, 224DA167-0C0C-11E8-8442-00059A3C7B00:1-2695"</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If there are, or might be, overlapping transactions between
the GTID sets in the dump files, you can use the stored
functions described in
<a class="xref" href="replication-gtids-functions.html" title="19.1.3.8 Stored Function Examples to Manipulate GTIDs">
Section 19.1.3.8, “Stored Function Examples to Manipulate GTIDs”
</a>
to check this
beforehand and to calculate the union of all the GTID sets.
</p>
</li>
</ol>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/gis-class-curve.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="gis-class-curve">
</a>
13.4.2.4 Curve Class
</h4>
</div>
</div>
</div>
<p>
A
<code class="literal">
Curve
</code>
is a one-dimensional geometry,
usually represented by a sequence of points. Particular
subclasses of
<code class="literal">
Curve
</code>
define the type of
interpolation between points.
<code class="literal">
Curve
</code>
is a
noninstantiable class.
</p>
<p>
<span class="bold">
<strong>
<code class="literal">
Curve
</code>
Properties
</strong>
</span>
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A
<code class="literal">
Curve
</code>
has the coordinates of its
points.
</p>
</li>
<li class="listitem">
<p>
A
<code class="literal">
Curve
</code>
is defined as a one-dimensional
geometry.
</p>
</li>
<li class="listitem">
<p>
A
<code class="literal">
Curve
</code>
is simple if it does not pass
through the same point twice, with the exception that a
curve can still be simple if the start and end points are
the same.
</p>
</li>
<li class="listitem">
<p>
A
<code class="literal">
Curve
</code>
is closed if its start point is
equal to its endpoint.
</p>
</li>
<li class="listitem">
<p>
The boundary of a closed
<code class="literal">
Curve
</code>
is
empty.
</p>
</li>
<li class="listitem">
<p>
The boundary of a nonclosed
<code class="literal">
Curve
</code>
consists of its two endpoints.
</p>
</li>
<li class="listitem">
<p>
A
<code class="literal">
Curve
</code>
that is simple and closed is a
<code class="literal">
LinearRing
</code>
.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-virtual-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="information-schema-innodb-virtual-table">
</a>
28.4.29 The INFORMATION_SCHEMA INNODB_VIRTUAL Table
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045076146128">
</a>
<p>
The
<a class="link" href="information-schema-innodb-virtual-table.html" title="28.4.29 The INFORMATION_SCHEMA INNODB_VIRTUAL Table">
<code class="literal">
INNODB_VIRTUAL
</code>
</a>
table provides
metadata about
<code class="literal">
InnoDB
</code>
<a class="link" href="glossary.html#glos_virtual_generated_column" title="virtual generated column">
virtual generated
columns
</a>
and columns upon which virtual generated columns
are based.
</p>
<p>
A row appears in the
<a class="link" href="information-schema-innodb-virtual-table.html" title="28.4.29 The INFORMATION_SCHEMA INNODB_VIRTUAL Table">
<code class="literal">
INNODB_VIRTUAL
</code>
</a>
table for each column upon which a virtual generated column is
based.
</p>
<p>
The
<a class="link" href="information-schema-innodb-virtual-table.html" title="28.4.29 The INFORMATION_SCHEMA INNODB_VIRTUAL Table">
<code class="literal">
INNODB_VIRTUAL
</code>
</a>
table has these
columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
TABLE_ID
</code>
</p>
<p>
An identifier representing the table associated with the
virtual column; the same value as
<code class="literal">
INNODB_TABLES.TABLE_ID
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
POS
</code>
</p>
<p>
The position value of the
<a class="link" href="glossary.html#glos_virtual_generated_column" title="virtual generated column">
virtual
generated column
</a>
. The value is large because it encodes
the column sequence number and ordinal position. The formula
used to calculate the value uses a bitwise operation:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-simple"><div class="docs-select-all right" id="sa9600309"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple"><span class="token punctuation">(</span><span class="token punctuation">(</span><em class="replaceable">n</em>th virtual generated column for the InnoDB instance <span class="token operator">+</span> 1<span class="token punctuation">)</span> <span class="token operator"><<</span> 16<span class="token punctuation">)</span>
<span class="token operator">+</span> the ordinal position of the virtual generated column</code></pre>
</div>
<p>
For example, if the first virtual generated column in the
<code class="literal">
InnoDB
</code>
instance is the third column of the
table, the formula is
<code class="literal">
(0 + 1) << 16) +
2
</code>
. The first virtual generated column in the
<code class="literal">
InnoDB
</code>
instance is always number 0. As the
third column in the table, the ordinal position of the virtual
generated column is 2. Ordinal positions are counted from 0.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
BASE_POS
</code>
</p>
<p>
The ordinal position of the columns upon which a virtual
generated column is based.
</p>
</li>
</ul>
</div>
<h4>
<a name="idm46045076125248">
</a>
Example
</h4>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa43141537"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>t1<span class="token punctuation">`</span> <span class="token punctuation">(</span>
<span class="token punctuation">`</span>a<span class="token punctuation">`</span> <span class="token datatype">int</span><span class="token punctuation">(</span><span class="token number">11</span><span class="token punctuation">)</span> <span class="token keyword">DEFAULT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>b<span class="token punctuation">`</span> <span class="token datatype">int</span><span class="token punctuation">(</span><span class="token number">11</span><span class="token punctuation">)</span> <span class="token keyword">DEFAULT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>c<span class="token punctuation">`</span> <span class="token datatype">int</span><span class="token punctuation">(</span><span class="token number">11</span><span class="token punctuation">)</span> <span class="token keyword">GENERATED</span> <span class="token keyword">ALWAYS</span> <span class="token keyword">AS</span> <span class="token punctuation">(</span>a<span class="token operator">+</span>b<span class="token punctuation">)</span> <span class="token keyword">VIRTUAL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>h<span class="token punctuation">`</span> <span class="token datatype">varchar</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token keyword">DEFAULT</span> <span class="token boolean">NULL</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span>InnoDB <span class="token keyword">DEFAULT</span> <span class="token keyword">CHARSET</span><span class="token operator">=</span>utf8mb4<span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_VIRTUAL
<span class="token keyword">WHERE</span> TABLE_ID <span class="token keyword">IN</span>
<span class="token punctuation">(</span><span class="token keyword">SELECT</span> TABLE_ID <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_TABLES
<span class="token keyword">WHERE</span> <span class="token keyword">NAME</span> <span class="token operator">LIKE</span> <span class="token string">"test/t1"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> TABLE_ID <span class="token punctuation">|</span> POS <span class="token punctuation">|</span> BASE_POS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 98 <span class="token punctuation">|</span> 65538 <span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 98 <span class="token punctuation">|</span> 65538 <span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<h4>
<a name="idm46045076116320">
</a>
Notes
</h4>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If a constant value is assigned to a
<a class="link" href="glossary.html#glos_virtual_generated_column" title="virtual generated column">
virtual
generated column
</a>
, as in the following table, an entry
for the column does not appear in the
<code class="literal">
INNODB_VIRTUAL
</code>
table. For an entry to
appear, a virtual generated column must have a base column.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa26535097"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>t1<span class="token punctuation">`</span> <span class="token punctuation">(</span>
<span class="token punctuation">`</span>a<span class="token punctuation">`</span> <span class="token datatype">int</span><span class="token punctuation">(</span><span class="token number">11</span><span class="token punctuation">)</span> <span class="token keyword">DEFAULT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>b<span class="token punctuation">`</span> <span class="token datatype">int</span><span class="token punctuation">(</span><span class="token number">11</span><span class="token punctuation">)</span> <span class="token keyword">DEFAULT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span>
<span class="token punctuation">`</span>c<span class="token punctuation">`</span> <span class="token datatype">int</span><span class="token punctuation">(</span><span class="token number">11</span><span class="token punctuation">)</span> <span class="token keyword">GENERATED</span> <span class="token keyword">ALWAYS</span> <span class="token keyword">AS</span> <span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span> <span class="token keyword">VIRTUAL</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span><span class="token operator">=</span>InnoDB <span class="token keyword">DEFAULT</span> <span class="token keyword">CHARSET</span><span class="token operator">=</span>utf8mb4<span class="token punctuation">;</span></code></pre>
</div>
<p>
However, metadata for such a column does appear in the
<a class="link" href="information-schema-innodb-columns-table.html" title="28.4.9 The INFORMATION_SCHEMA INNODB_COLUMNS Table">
<code class="literal">
INNODB_COLUMNS
</code>
</a>
table.
</p>
</li>
<li class="listitem">
<p>
You must have the
<a class="link" href="privileges-provided.html#priv_process">
<code class="literal">
PROCESS
</code>
</a>
privilege to query this table.
</p>
</li>
<li class="listitem">
<p>
Use the
<code class="literal">
INFORMATION_SCHEMA
</code>
<a class="link" href="information-schema-columns-table.html" title="28.3.8 The INFORMATION_SCHEMA COLUMNS Table">
<code class="literal">
COLUMNS
</code>
</a>
table or the
<a class="link" href="show-columns.html" title="15.7.7.6 SHOW COLUMNS Statement">
<code class="literal">
SHOW COLUMNS
</code>
</a>
statement to view
additional information about the columns of this table,
including data types and default values.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/identifier-qualifiers.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="identifier-qualifiers">
</a>
11.2.2 Identifier Qualifiers
</h3>
</div>
</div>
</div>
<p>
Object names may be unqualified or qualified. An unqualified
name is permitted in contexts where interpretation of the name
is unambiguous. A qualified name includes at least one qualifier
to clarify the interpretive context by overriding a default
context or providing missing context.
</p>
<p>
For example, this statement creates a table using the
unqualified name
<code class="literal">
t1
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa65330541"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span>i <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Because
<code class="literal">
t1
</code>
includes no qualifier to specify a
database, the statement creates the table in the default
database. If there is no default database, an error occurs.
</p>
<p>
This statement creates a table using the qualified name
<code class="literal">
db1.t1
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa15696632"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> db1<span class="token punctuation">.</span>t1 <span class="token punctuation">(</span>i <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Because
<code class="literal">
db1.t1
</code>
includes a database qualifier
<code class="literal">
db1
</code>
, the statement creates
<code class="literal">
t1
</code>
in the database named
<code class="literal">
db1
</code>
, regardless of the default database. The
qualifier
<span class="emphasis">
<em>
must
</em>
</span>
be specified if there is no
default database. The qualifier
<span class="emphasis">
<em>
may
</em>
</span>
be
specified if there is a default database, to specify a database
different from the default, or to make the database explicit if
the default is the same as the one specified.
</p>
<p>
Qualifiers have these characteristics:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
An unqualified name consists of a single identifier. A
qualified name consists of multiple identifiers.
</p>
</li>
<li class="listitem">
<p>
The components of a multiple-part name must be separated by
period (
<code class="literal">
.
</code>
) characters. The initial parts
of a multiple-part name act as qualifiers that affect the
context within which to interpret the final identifier.
</p>
</li>
<li class="listitem">
<p>
The qualifier character is a separate token and need not be
contiguous with the associated identifiers. For example,
<em class="replaceable">
<code>
tbl_name.col_name
</code>
</em>
and
<em class="replaceable">
<code>
tbl_name . col_name
</code>
</em>
are
equivalent.
</p>
</li>
<li class="listitem">
<p>
If any components of a multiple-part name require quoting,
quote them individually rather than quoting the name as a
whole. For example, write
<code class="literal">
`my-table`.`my-column`
</code>
, not
<code class="literal">
`my-table.my-column`
</code>
.
</p>
</li>
<li class="listitem">
<p>
A reserved word that follows a period in a qualified name
must be an identifier, so in that context it need not be
quoted.
</p>
</li>
</ul>
</div>
<p>
The permitted qualifiers for object names depend on the object
type:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A database name is fully qualified and takes no qualifier:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa16482361"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">DATABASE</span> db1<span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
A table, view, or stored program name may be given a
database-name qualifier. Examples of unqualified and
qualified names in
<code class="literal">
CREATE
</code>
statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa90218257"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> mytable <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">VIEW</span> myview <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">PROCEDURE</span> myproc <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> myfunc <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">EVENT</span> myevent <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> mydb<span class="token punctuation">.</span>mytable <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">VIEW</span> mydb<span class="token punctuation">.</span>myview <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">PROCEDURE</span> mydb<span class="token punctuation">.</span>myproc <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> mydb<span class="token punctuation">.</span>myfunc <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">EVENT</span> mydb<span class="token punctuation">.</span>myevent <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
A trigger is associated with a table, so any qualifier
applies to the table name:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa245474"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TRIGGER</span> mytrigger <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">ON</span> mytable <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TRIGGER</span> mytrigger <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">ON</span> mydb<span class="token punctuation">.</span>mytable <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
A column name may be given multiple qualifiers to indicate
context in statements that reference it, as shown in the
following table.
</p>
<div class="informaltable">
<table summary="Column reference formats that can be used to refer to table columns.">
<colgroup>
<col style="width: 35%"/>
<col style="width: 65%"/>
</colgroup>
<thead>
<tr>
<th>
Column Reference
</th>
<th>
Meaning
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<em class="replaceable">
<code>
col_name
</code>
</em>
</td>
<td>
Column
<em class="replaceable">
<code>
col_name
</code>
</em>
from whichever table used in
the statement contains a column of that name
</td>
</tr>
<tr>
<td>
<em class="replaceable">
<code>
tbl_name.col_name
</code>
</em>
</td>
<td>
Column
<em class="replaceable">
<code>
col_name
</code>
</em>
from table
<em class="replaceable">
<code>
tbl_name
</code>
</em>
of the default
database
</td>
</tr>
<tr>
<td>
<em class="replaceable">
<code>
db_name.tbl_name.col_name
</code>
</em>
</td>
<td>
Column
<em class="replaceable">
<code>
col_name
</code>
</em>
from table
<em class="replaceable">
<code>
tbl_name
</code>
</em>
of the database
<em class="replaceable">
<code>
db_name
</code>
</em>
</td>
</tr>
</tbody>
</table>
</div>
<p>
In other words, a column name may be given a table-name
qualifier, which itself may be given a database-name
qualifier. Examples of unqualified and qualified column
references in
<code class="literal">
SELECT
</code>
statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa39650435"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> c1 <span class="token keyword">FROM</span> mytable
<span class="token keyword">WHERE</span> c2 <span class="token operator">></span> <span class="token number">100</span><span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> mytable<span class="token punctuation">.</span>c1 <span class="token keyword">FROM</span> mytable
<span class="token keyword">WHERE</span> mytable<span class="token punctuation">.</span>c2 <span class="token operator">></span> <span class="token number">100</span><span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> mydb<span class="token punctuation">.</span>mytable<span class="token punctuation">.</span>c1 <span class="token keyword">FROM</span> mydb<span class="token punctuation">.</span>mytable
<span class="token keyword">WHERE</span> mydb<span class="token punctuation">.</span>mytable<span class="token punctuation">.</span>c2 <span class="token operator">></span> <span class="token number">100</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
You need not specify a qualifier for an object reference in a
statement unless the unqualified reference is ambiguous. Suppose
that column
<code class="literal">
c1
</code>
occurs only in table
<code class="literal">
t1
</code>
,
<code class="literal">
c2
</code>
only in
<code class="literal">
t2
</code>
, and
<code class="literal">
c
</code>
in both
<code class="literal">
t1
</code>
and
<code class="literal">
t2
</code>
. Any unqualified
reference to
<code class="literal">
c
</code>
is ambiguous in a statement
that refers to both tables and must be qualified as
<code class="literal">
t1.c
</code>
or
<code class="literal">
t2.c
</code>
to indicate
which table you mean:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa85257659"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">,</span> t1<span class="token punctuation">.</span>c <span class="token keyword">FROM</span> t1 <span class="token keyword">INNER</span> <span class="token keyword">JOIN</span> t2
<span class="token keyword">WHERE</span> t2<span class="token punctuation">.</span>c <span class="token operator">></span> <span class="token number">100</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Similarly, to retrieve from a table
<code class="literal">
t
</code>
in
database
<code class="literal">
db1
</code>
and from a table
<code class="literal">
t
</code>
in database
<code class="literal">
db2
</code>
in the
same statement, you must qualify the table references: For
references to columns in those tables, qualifiers are required
only for column names that appear in both tables. Suppose that
column
<code class="literal">
c1
</code>
occurs only in table
<code class="literal">
db1.t
</code>
,
<code class="literal">
c2
</code>
only in
<code class="literal">
db2.t
</code>
, and
<code class="literal">
c
</code>
in both
<code class="literal">
db1.t
</code>
and
<code class="literal">
db2.t
</code>
. In this
case,
<code class="literal">
c
</code>
is ambiguous and must be qualified
but
<code class="literal">
c1
</code>
and
<code class="literal">
c2
</code>
need not be:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa48686383"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">,</span> db1<span class="token punctuation">.</span>t<span class="token punctuation">.</span>c <span class="token keyword">FROM</span> db1<span class="token punctuation">.</span>t <span class="token keyword">INNER</span> <span class="token keyword">JOIN</span> db2<span class="token punctuation">.</span>t
<span class="token keyword">WHERE</span> db2<span class="token punctuation">.</span>t<span class="token punctuation">.</span>c <span class="token operator">></span> <span class="token number">100</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Table aliases enable qualified column references to be written
more simply:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51250567"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> c1<span class="token punctuation">,</span> c2<span class="token punctuation">,</span> t1<span class="token punctuation">.</span>c <span class="token keyword">FROM</span> db1<span class="token punctuation">.</span>t <span class="token keyword">AS</span> t1 <span class="token keyword">INNER</span> <span class="token keyword">JOIN</span> db2<span class="token punctuation">.</span>t <span class="token keyword">AS</span> t2
<span class="token keyword">WHERE</span> t2<span class="token punctuation">.</span>c <span class="token operator">></span> <span class="token number">100</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/other-administrative-statements.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="other-administrative-statements">
</a>
15.7.8 Other Administrative Statements
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="binlog.html">
15.7.8.1 BINLOG Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="cache-index.html">
15.7.8.2 CACHE INDEX Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="flush.html">
15.7.8.3 FLUSH Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="kill.html">
15.7.8.4 KILL Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="load-index.html">
15.7.8.5 LOAD INDEX INTO CACHE Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="reset.html">
15.7.8.6 RESET Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="reset-persist.html">
15.7.8.7 RESET PERSIST Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="restart.html">
15.7.8.8 RESTART Statement
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="shutdown.html">
15.7.8.9 SHUTDOWN Statement
</a>
</span>
</dt>
</dl>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/show-create-database.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="show-create-database">
</a>
15.7.7.7 SHOW CREATE DATABASE Statement
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045170960544">
</a>
<a class="indexterm" name="idm46045170959488">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa39712200"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SHOW</span> <span class="token keyword">CREATE</span> {<span class="token keyword">DATABASE</span> <span class="token operator">|</span> <span class="token keyword">SCHEMA</span>} <span class="token punctuation">[</span><span class="token keyword">IF</span> <span class="token operator">NOT</span> <span class="token keyword">EXISTS</span><span class="token punctuation">]</span> <em class="replaceable">db_name</em></code></pre>
</div>
<p>
Shows the
<a class="link" href="create-database.html" title="15.1.12 CREATE DATABASE Statement">
<code class="literal">
CREATE DATABASE
</code>
</a>
statement that creates the named database. If the
<code class="literal">
SHOW
</code>
statement includes an
<code class="literal">
IF NOT
EXISTS
</code>
clause, the output too includes such a clause.
<a class="link" href="show-create-database.html" title="15.7.7.7 SHOW CREATE DATABASE Statement">
<code class="literal">
SHOW
CREATE SCHEMA
</code>
</a>
is a synonym for
<a class="link" href="show-create-database.html" title="15.7.7.7 SHOW CREATE DATABASE Statement">
<code class="literal">
SHOW CREATE DATABASE
</code>
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa39707235"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">CREATE</span> <span class="token keyword">DATABASE</span> test\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
Database<span class="token punctuation">:</span> test
Create Database<span class="token punctuation">:</span> CREATE DATABASE `test` /<span class="token punctuation">*</span>!40100 DEFAULT CHARACTER SET utf8mb4
COLLATE utf8mb4_0900_ai_ci <span class="token punctuation">*</span>/ /<span class="token punctuation">*</span>!80014 DEFAULT ENCRYPTION='N' <span class="token punctuation">*</span>/
</span>
<span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">CREATE</span> <span class="token keyword">SCHEMA</span> test\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
Database<span class="token punctuation">:</span> test
Create Database<span class="token punctuation">:</span> CREATE DATABASE `test` /<span class="token punctuation">*</span>!40100 DEFAULT CHARACTER SET utf8mb4
COLLATE utf8mb4_0900_ai_ci <span class="token punctuation">*</span>/ /<span class="token punctuation">*</span>!80014 DEFAULT ENCRYPTION='N' <span class="token punctuation">*</span>/</span></code></pre>
</div>
<p>
<a class="link" href="show-create-database.html" title="15.7.7.7 SHOW CREATE DATABASE Statement">
<code class="literal">
SHOW CREATE DATABASE
</code>
</a>
quotes table
and column names according to the value of the
<a class="link" href="server-system-variables.html#sysvar_sql_quote_show_create">
<code class="literal">
sql_quote_show_create
</code>
</a>
option.
See
<a class="xref" href="server-system-variables.html" title="7.1.8 Server System Variables">
Section 7.1.8, “Server System Variables”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/workbench.html | <div id="docs-body">
<div class="chapter">
<div class="titlepage">
<div>
<div>
<h1 class="title">
<a name="workbench">
</a>
Chapter 33 MySQL Workbench
</h1>
</div>
</div>
</div>
<p>
MySQL Workbench provides a graphical tool for working with MySQL servers
and databases. MySQL Workbench fully supports MySQL versions 5.5 and
higher.
</p>
<p>
The following discussion briefly describes MySQL Workbench capabilities.
For more information, see the MySQL Workbench manual, available at
<a class="ulink" href="/doc/workbench/en/" target="_top">
https://dev.mysql.com/doc/workbench/en/
</a>
.
</p>
<p>
MySQL Workbench provides five main areas of functionality:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<span class="bold">
<strong>
SQL Development
</strong>
</span>
: Enables you to
create and manage connections to database servers. As well as
enabling you to configure connection parameters, MySQL Workbench
provides the capability to execute SQL queries on the database
connections using the built-in SQL Editor. This functionality
replaces that previously provided by the Query Browser
standalone application.
</p>
</li>
<li class="listitem">
<p>
<span class="bold">
<strong>
Data Modeling
</strong>
</span>
: Enables you to
create models of your database schema graphically, reverse and
forward engineer between a schema and a live database, and edit
all aspects of your database using the comprehensive Table
Editor. The Table Editor provides easy-to-use facilities for
editing Tables, Columns, Indexes, Triggers, Partitioning,
Options, Inserts and Privileges, Routines and Views.
</p>
</li>
<li class="listitem">
<p>
<span class="bold">
<strong>
Server Administration
</strong>
</span>
: Enables
you to create and administer server instances.
</p>
</li>
<li class="listitem">
<p>
<span class="bold">
<strong>
Data Migration
</strong>
</span>
: Allows you to
migrate from Microsoft SQL Server, Sybase ASE, SQLite, SQL
Anywhere, PostreSQL, and other RDBMS tables, objects and data to
MySQL. Migration also supports migrating from earlier versions
of MySQL to the latest releases.
</p>
</li>
<li class="listitem">
<p>
<span class="bold">
<strong>
MySQL Enterprise Support
</strong>
</span>
:
Support for Enterprise products such as MySQL Enterprise Backup and MySQL Audit.
</p>
</li>
</ul>
</div>
<p>
MySQL Workbench is available in two editions, the Community Edition and
the Commercial Edition. The Community Edition is available free of
charge. The Commercial Edition provides additional Enterprise
features, such as database documentation generation, at low cost.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/optimizer-trace-testing.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="optimizer-trace-testing">
</a>
10.15.15 Testing Optimizer Trace
</h3>
</div>
</div>
</div>
<p>
This feature is tested in
<code class="filename">
mysql-test/suite/opt_trace
</code>
and
<code class="filename">
unittest/gunit/opt_trace-t
</code>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/macos-installation.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="macos-installation">
</a>
2.4 Installing MySQL on macOS
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="macos-installation-notes.html">
2.4.1 General Notes on Installing MySQL on macOS
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="macos-installation-pkg.html">
2.4.2 Installing MySQL on macOS Using Native Packages
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="macos-installation-launchd.html">
2.4.3 Installing and Using the MySQL Launch Daemon
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="macos-installation-prefpane.html">
2.4.4 Installing and Using the MySQL Preference Pane
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045331698080">
</a>
<a class="indexterm" name="idm46045331696624">
</a>
<p>
For a list of macOS versions that the MySQL server supports, see
<a class="ulink" href="https://www.mysql.com/support/supportedplatforms/database.html" target="_blank">
https://www.mysql.com/support/supportedplatforms/database.html
</a>
.
</p>
<p>
MySQL for macOS is available in a number of different forms:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Native Package Installer, which uses the native macOS installer
(DMG) to walk you through the installation of MySQL. For more
information, see
<a class="xref" href="macos-installation-pkg.html" title="2.4.2 Installing MySQL on macOS Using Native Packages">
Section 2.4.2, “Installing MySQL on macOS Using Native Packages”
</a>
. You
can use the package installer with macOS. The user you use to
perform the installation must have administrator privileges.
</p>
</li>
<li class="listitem">
<p>
Compressed TAR archive, which uses a file packaged using the
Unix
<span class="command">
<strong>
tar
</strong>
</span>
and
<span class="command">
<strong>
gzip
</strong>
</span>
commands. To use this method, you need to open a
<span class="command">
<strong>
Terminal
</strong>
</span>
window. You do not need
administrator privileges using this method; you can install the
MySQL server anywhere using this method. For more information on
using this method, you can use the generic instructions for
using a tarball,
<a class="xref" href="binary-installation.html" title="2.2 Installing MySQL on Unix/Linux Using Generic Binaries">
Section 2.2, “Installing MySQL on Unix/Linux Using Generic Binaries”
</a>
.
</p>
<p>
In addition to the core installation, the Package Installer also
includes
<a class="xref" href="macos-installation-launchd.html" title="2.4.3 Installing and Using the MySQL Launch Daemon">
Section 2.4.3, “Installing and Using the MySQL Launch Daemon”
</a>
and
<a class="xref" href="macos-installation-prefpane.html" title="2.4.4 Installing and Using the MySQL Preference Pane">
Section 2.4.4, “Installing and Using the MySQL Preference Pane”
</a>
to simplify the
management of your installation.
</p>
</li>
</ul>
</div>
<p>
For additional information on using MySQL on macOS, see
<a class="xref" href="macos-installation-notes.html" title="2.4.1 General Notes on Installing MySQL on macOS">
Section 2.4.1, “General Notes on Installing MySQL on macOS”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-session-account-connect-attrs-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="performance-schema-session-account-connect-attrs-table">
</a>
29.12.9.1 The session_account_connect_attrs Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045071848976">
</a>
<a class="indexterm" name="idm46045071847472">
</a>
<p>
Application programs can provide key-value connection
attributes to be passed to the server at connect time. For
descriptions of common attributes, see
<a class="xref" href="performance-schema-connection-attribute-tables.html" title="29.12.9 Performance Schema Connection Attribute Tables">
Section 29.12.9, “Performance Schema Connection Attribute Tables”
</a>
.
</p>
<p>
The
<a class="link" href="performance-schema-session-account-connect-attrs-table.html" title="29.12.9.1 The session_account_connect_attrs Table">
<code class="literal">
session_account_connect_attrs
</code>
</a>
table contains connection attributes only for the current
session, and other sessions associated with the session
account. To see connection attributes for all sessions, use
the
<a class="link" href="performance-schema-session-connect-attrs-table.html" title="29.12.9.2 The session_connect_attrs Table">
<code class="literal">
session_connect_attrs
</code>
</a>
table.
</p>
<p>
The
<a class="link" href="performance-schema-session-account-connect-attrs-table.html" title="29.12.9.1 The session_account_connect_attrs Table">
<code class="literal">
session_account_connect_attrs
</code>
</a>
table has these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
PROCESSLIST_ID
</code>
</p>
<p>
The connection identifier for the session.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ATTR_NAME
</code>
</p>
<p>
The attribute name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ATTR_VALUE
</code>
</p>
<p>
The attribute value.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ORDINAL_POSITION
</code>
</p>
<p>
The order in which the attribute was added to the set of
connection attributes.
</p>
</li>
</ul>
</div>
<p>
The
<a class="link" href="performance-schema-session-account-connect-attrs-table.html" title="29.12.9.1 The session_account_connect_attrs Table">
<code class="literal">
session_account_connect_attrs
</code>
</a>
table has these indexes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Primary key on (
<code class="literal">
PROCESSLIST_ID
</code>
,
<code class="literal">
ATTR_NAME
</code>
)
</p>
</li>
</ul>
</div>
<p>
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
is not permitted
for the
<a class="link" href="performance-schema-session-account-connect-attrs-table.html" title="29.12.9.1 The session_account_connect_attrs Table">
<code class="literal">
session_account_connect_attrs
</code>
</a>
table.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-deploying-in-multi-primary-or-single-primary-mode.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="group-replication-deploying-in-multi-primary-or-single-primary-mode">
</a>
20.1.3 Multi-Primary and Single-Primary Modes
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="group-replication-single-primary-mode.html">
20.1.3.1 Single-Primary Mode
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="group-replication-multi-primary-mode.html">
20.1.3.2 Multi-Primary Mode
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045134507856">
</a>
<a class="indexterm" name="idm46045134506352">
</a>
<a class="indexterm" name="idm46045134504864">
</a>
<p>
Group Replication operates either in single-primary mode or in
multi-primary mode. The group's mode is a group-wide configuration
setting, specified by the
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_single_primary_mode">
<code class="literal">
group_replication_single_primary_mode
</code>
</a>
system variable, which must be the same on all members.
<code class="literal">
ON
</code>
means single-primary mode, which is the
default mode, and
<code class="literal">
OFF
</code>
means multi-primary mode.
It is not possible to have members of the group deployed in
different modes, for example one member configured in
multi-primary mode while another member is in single-primary mode.
</p>
<p>
You cannot change the value of
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_single_primary_mode">
<code class="literal">
group_replication_single_primary_mode
</code>
</a>
manually while Group Replication is running. You can use the
<a class="link" href="group-replication-functions-for-mode.html#function_group-replication-switch-to-single-primary-mode">
<code class="literal">
group_replication_switch_to_single_primary_mode()
</code>
</a>
and
<a class="link" href="group-replication-functions-for-mode.html#function_group-replication-switch-to-multi-primary-mode">
<code class="literal">
group_replication_switch_to_multi_primary_mode()
</code>
</a>
functions to move a group from one mode to another while Group
Replication is still running. These functions manage the process
of changing the group's mode and ensure the safety and consistency
of your data. In earlier releases, to change the group's mode you
must stop Group Replication and change the value of
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_single_primary_mode">
<code class="literal">
group_replication_single_primary_mode
</code>
</a>
on all members. Then carry out a full reboot of the group (a
bootstrap by a server with
<a class="link" href="group-replication-system-variables.html#sysvar_group_replication_bootstrap_group">
<code class="literal">
group_replication_bootstrap_group=ON
</code>
</a>
)
to implement the change to the new operating configuration. You do
not need to restart the servers.
</p>
<p>
Regardless of the deployed mode, Group Replication does not handle
client-side failover. That must be handled by a middleware
framework such as
<a class="ulink" href="/doc/mysql-router/8.4/en/" target="_top">
MySQL Router 8.4
</a>
, a proxy, a
connector, or the application itself.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/gis-linestring-property-functions.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="gis-linestring-property-functions">
</a>
14.16.7.3 LineString and MultiLineString Property Functions
</h4>
</div>
</div>
</div>
<p>
A
<code class="literal">
LineString
</code>
consists of
<code class="literal">
Point
</code>
values. You can extract particular
points of a
<code class="literal">
LineString
</code>
, count the number of
points that it contains, or obtain its length.
</p>
<p>
Some functions in this section also work for
<code class="literal">
MultiLineString
</code>
values.
</p>
<p>
Unless otherwise specified, functions in this section handle
their geometry arguments as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If any argument is
<code class="literal">
NULL
</code>
or any geometry
argument is an empty geometry, the return value is
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
If any geometry argument is not a syntactically well-formed
geometry, an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_gis_invalid_data" target="_top">
<code class="literal">
ER_GIS_INVALID_DATA
</code>
</a>
error
occurs.
</p>
</li>
<li class="listitem">
<p>
If any geometry argument is a syntactically well-formed
geometry in an undefined spatial reference system (SRS), an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_srs_not_found" target="_top">
<code class="literal">
ER_SRS_NOT_FOUND
</code>
</a>
error
occurs.
</p>
</li>
<li class="listitem">
<p>
Otherwise, the return value is non-
<code class="literal">
NULL
</code>
.
</p>
</li>
</ul>
</div>
<p>
These functions are available for obtaining linestring
properties:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<a name="function_st-endpoint">
</a>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-endpoint">
<code class="literal">
ST_EndPoint(
<em class="replaceable">
<code>
ls
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045197305024">
</a>
<p>
Returns the
<code class="literal">
Point
</code>
that is the endpoint of
the
<code class="literal">
LineString
</code>
value
<em class="replaceable">
<code>
ls
</code>
</em>
.
</p>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-endpoint">
<code class="literal">
ST_EndPoint()
</code>
</a>
handles its
arguments as described in the introduction to this section.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa79717437"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls</span> <span class="token operator">=</span> <span class="token string">'LineString(1 1,2 2,3 3)'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_AsText</span><span class="token punctuation">(</span><span class="token function">ST_EndPoint</span><span class="token punctuation">(</span><span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token variable">@ls</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_AsText(ST_EndPoint(ST_GeomFromText(@ls))) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> POINT(3 3) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_st-isclosed">
</a>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-isclosed">
<code class="literal">
ST_IsClosed(
<em class="replaceable">
<code>
ls
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045197291424">
</a>
<p>
For a
<code class="literal">
LineString
</code>
value
<em class="replaceable">
<code>
ls
</code>
</em>
,
<a class="link" href="gis-linestring-property-functions.html#function_st-isclosed">
<code class="literal">
ST_IsClosed()
</code>
</a>
returns 1 if
<em class="replaceable">
<code>
ls
</code>
</em>
is closed (that is, its
<a class="link" href="gis-linestring-property-functions.html#function_st-startpoint">
<code class="literal">
ST_StartPoint()
</code>
</a>
and
<a class="link" href="gis-linestring-property-functions.html#function_st-endpoint">
<code class="literal">
ST_EndPoint()
</code>
</a>
values are the
same).
</p>
<p>
For a
<code class="literal">
MultiLineString
</code>
value
<em class="replaceable">
<code>
ls
</code>
</em>
,
<a class="link" href="gis-linestring-property-functions.html#function_st-isclosed">
<code class="literal">
ST_IsClosed()
</code>
</a>
returns 1 if
<em class="replaceable">
<code>
ls
</code>
</em>
is closed (that is, the
<a class="link" href="gis-linestring-property-functions.html#function_st-startpoint">
<code class="literal">
ST_StartPoint()
</code>
</a>
and
<a class="link" href="gis-linestring-property-functions.html#function_st-endpoint">
<code class="literal">
ST_EndPoint()
</code>
</a>
values are the
same for each
<code class="literal">
LineString
</code>
in
<em class="replaceable">
<code>
ls
</code>
</em>
).
</p>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-isclosed">
<code class="literal">
ST_IsClosed()
</code>
</a>
returns 0 if
<em class="replaceable">
<code>
ls
</code>
</em>
is not closed, and
<code class="literal">
NULL
</code>
if
<em class="replaceable">
<code>
ls
</code>
</em>
is
<code class="literal">
NULL
</code>
.
</p>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-isclosed">
<code class="literal">
ST_IsClosed()
</code>
</a>
handles its
arguments as described in the introduction to this section,
with this exception:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If the geometry has an SRID value for a geographic
spatial reference system (SRS), an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_not_implemented_for_geographic_srs" target="_top">
<code class="literal">
ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS
</code>
</a>
error occurs.
</p>
</li>
</ul>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa89716030"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls1</span> <span class="token operator">=</span> <span class="token string">'LineString(1 1,2 2,3 3,2 2)'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls2</span> <span class="token operator">=</span> <span class="token string">'LineString(1 1,2 2,3 3,1 1)'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_IsClosed</span><span class="token punctuation">(</span><span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token variable">@ls1</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_IsClosed(ST_GeomFromText(@ls1)) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_IsClosed</span><span class="token punctuation">(</span><span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token variable">@ls2</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_IsClosed(ST_GeomFromText(@ls2)) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls3</span> <span class="token operator">=</span> <span class="token string">'MultiLineString((1 1,2 2,3 3),(4 4,5 5))'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_IsClosed</span><span class="token punctuation">(</span><span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token variable">@ls3</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_IsClosed(ST_GeomFromText(@ls3)) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 0 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_st-length">
</a>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-length">
<code class="literal">
ST_Length(
<em class="replaceable">
<code>
ls
</code>
</em>
[,
<em class="replaceable">
<code>
unit
</code>
</em>
])
</code>
</a>
</p>
<a class="indexterm" name="idm46045197256848">
</a>
<p>
Returns a double-precision number indicating the length of
the
<code class="literal">
LineString
</code>
or
<code class="literal">
MultiLineString
</code>
value
<em class="replaceable">
<code>
ls
</code>
</em>
in its associated spatial
reference system. The length of a
<code class="literal">
MultiLineString
</code>
value is equal to the sum
of the lengths of its elements.
</p>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-length">
<code class="literal">
ST_Length()
</code>
</a>
computes a result
as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If the geometry is a valid
<code class="literal">
LineString
</code>
in a Cartesian SRS, the return value is the Cartesian
length of the geometry.
</p>
</li>
<li class="listitem">
<p>
If the geometry is a valid
<code class="literal">
MultiLineString
</code>
in a Cartesian SRS,
the return value is the sum of the Cartesian lengths of
its elements.
</p>
</li>
<li class="listitem">
<p>
If the geometry is a valid
<code class="literal">
LineString
</code>
in a geographic SRS, the return value is the geodetic
length of the geometry in that SRS, in meters.
</p>
</li>
<li class="listitem">
<p>
If the geometry is a valid
<code class="literal">
MultiLineString
</code>
in a geographic SRS,
the return value is the sum of the geodetic lengths of
its elements in that SRS, in meters.
</p>
</li>
</ul>
</div>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-length">
<code class="literal">
ST_Length()
</code>
</a>
handles its
arguments as described in the introduction to this section,
with these exceptions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If the geometry is not a
<code class="literal">
LineString
</code>
or
<code class="literal">
MultiLineString
</code>
, the return value
is
<code class="literal">
NULL
</code>
.
</p>
</li>
<li class="listitem">
<p>
If the geometry is geometrically invalid, either the
result is an undefined length (that is, it can be any
number), or an error occurs.
</p>
</li>
<li class="listitem">
<p>
If the length computation result is
<code class="literal">
+inf
</code>
, an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_data_out_of_range" target="_top">
<code class="literal">
ER_DATA_OUT_OF_RANGE
</code>
</a>
error occurs.
</p>
</li>
<li class="listitem">
<p>
If the geometry has a geographic SRS with a longitude or
latitude that is out of range, an error occurs:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: square; ">
<li class="listitem">
<p>
If a longitude value is not in the range
(−180, 180], an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_geometry_param_longitude_out_of_range" target="_top">
<code class="literal">
ER_GEOMETRY_PARAM_LONGITUDE_OUT_OF_RANGE
</code>
</a>
error occurs.
</p>
</li>
<li class="listitem">
<p>
If a latitude value is not in the range [−90,
90], an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_geometry_param_latitude_out_of_range" target="_top">
<code class="literal">
ER_GEOMETRY_PARAM_LATITUDE_OUT_OF_RANGE
</code>
</a>
error occurs.
</p>
</li>
</ul>
</div>
<p>
Ranges shown are in degrees. The exact range limits
deviate slightly due to floating-point arithmetic.
</p>
</li>
</ul>
</div>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-length">
<code class="literal">
ST_Length()
</code>
</a>
permits an
optional
<em class="replaceable">
<code>
unit
</code>
</em>
argument that
specifies the linear unit for the returned length value.
These rules apply:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
If a unit is specified but not supported by MySQL, an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_unit_not_found" target="_top">
<code class="literal">
ER_UNIT_NOT_FOUND
</code>
</a>
error
occurs.
</p>
</li>
<li class="listitem">
<p>
If a supported linear unit is specified and the SRID is
0, an
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_geometry_in_unknown_length_unit" target="_top">
<code class="literal">
ER_GEOMETRY_IN_UNKNOWN_LENGTH_UNIT
</code>
</a>
error occurs.
</p>
</li>
<li class="listitem">
<p>
If a supported linear unit is specified and the SRID is
not 0, the result is in that unit.
</p>
</li>
<li class="listitem">
<p>
If a unit is not specified, the result is in the unit of
the SRS of the geometries, whether Cartesian or
geographic. Currently, all MySQL SRSs are expressed in
meters.
</p>
</li>
</ul>
</div>
<p>
A unit is supported if it is found in the
<code class="literal">
INFORMATION_SCHEMA
</code>
<a class="link" href="information-schema-st-units-of-measure-table.html" title="28.3.37 The INFORMATION_SCHEMA ST_UNITS_OF_MEASURE Table">
<code class="literal">
ST_UNITS_OF_MEASURE
</code>
</a>
table. See
<a class="xref" href="information-schema-st-units-of-measure-table.html" title="28.3.37 The INFORMATION_SCHEMA ST_UNITS_OF_MEASURE Table">
Section 28.3.37, “The INFORMATION_SCHEMA ST_UNITS_OF_MEASURE Table”
</a>
.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa82227910"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LineString(1 1,2 2,3 3)'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_Length</span><span class="token punctuation">(</span><span class="token variable">@ls</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_Length(@ls) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 2.8284271247461903 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@mls</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'MultiLineString((1 1,2 2,3 3),(4 4,5 5))'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_Length</span><span class="token punctuation">(</span><span class="token variable">@mls</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_Length(@mls) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 4.242640687119286 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls</span> <span class="token operator">=</span> <span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token string">'LineString(1 1,2 2,3 3)'</span><span class="token punctuation">,</span> <span class="token number">4326</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_Length</span><span class="token punctuation">(</span><span class="token variable">@ls</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_Length(@ls) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 313701.9623204328 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_Length</span><span class="token punctuation">(</span><span class="token variable">@ls</span><span class="token punctuation">,</span> <span class="token string">'metre'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_Length(@ls, 'metre') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 313701.9623204328 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_Length</span><span class="token punctuation">(</span><span class="token variable">@ls</span><span class="token punctuation">,</span> <span class="token string">'foot'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_Length(@ls, 'foot') <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1029205.9131247795 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_st-numpoints">
</a>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-numpoints">
<code class="literal">
ST_NumPoints(
<em class="replaceable">
<code>
ls
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045197202464">
</a>
<p>
Returns the number of
<code class="literal">
Point
</code>
objects in
the
<code class="literal">
LineString
</code>
value
<em class="replaceable">
<code>
ls
</code>
</em>
.
</p>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-numpoints">
<code class="literal">
ST_NumPoints()
</code>
</a>
handles its
arguments as described in the introduction to this section.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa30300123"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls</span> <span class="token operator">=</span> <span class="token string">'LineString(1 1,2 2,3 3)'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_NumPoints</span><span class="token punctuation">(</span><span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token variable">@ls</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_NumPoints(ST_GeomFromText(@ls)) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 3 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_st-pointn">
</a>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-pointn">
<code class="literal">
ST_PointN(
<em class="replaceable">
<code>
ls
</code>
</em>
,
<em class="replaceable">
<code>
N
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045197188512">
</a>
<p>
Returns the
<em class="replaceable">
<code>
N
</code>
</em>
-th
<code class="literal">
Point
</code>
in the
<code class="literal">
Linestring
</code>
value
<em class="replaceable">
<code>
ls
</code>
</em>
. Points are numbered beginning
with 1.
</p>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-pointn">
<code class="literal">
ST_PointN()
</code>
</a>
handles its
arguments as described in the introduction to this section.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa59191454"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls</span> <span class="token operator">=</span> <span class="token string">'LineString(1 1,2 2,3 3)'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_AsText</span><span class="token punctuation">(</span><span class="token function">ST_PointN</span><span class="token punctuation">(</span><span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token variable">@ls</span><span class="token punctuation">)</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_AsText(ST_PointN(ST_GeomFromText(@ls),2)) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> POINT(2 2) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
<li class="listitem">
<a name="function_st-startpoint">
</a>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-startpoint">
<code class="literal">
ST_StartPoint(
<em class="replaceable">
<code>
ls
</code>
</em>
)
</code>
</a>
</p>
<a class="indexterm" name="idm46045197174480">
</a>
<p>
Returns the
<code class="literal">
Point
</code>
that is the start point
of the
<code class="literal">
LineString
</code>
value
<em class="replaceable">
<code>
ls
</code>
</em>
.
</p>
<p>
<a class="link" href="gis-linestring-property-functions.html#function_st-startpoint">
<code class="literal">
ST_StartPoint()
</code>
</a>
handles its
arguments as described in the introduction to this section.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa8042608"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token variable">@ls</span> <span class="token operator">=</span> <span class="token string">'LineString(1 1,2 2,3 3)'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token function">ST_AsText</span><span class="token punctuation">(</span><span class="token function">ST_StartPoint</span><span class="token punctuation">(</span><span class="token function">ST_GeomFromText</span><span class="token punctuation">(</span><span class="token variable">@ls</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> ST_AsText(ST_StartPoint(ST_GeomFromText(@ls))) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> POINT(1 1) <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-deadlocks-handling.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="innodb-deadlocks-handling">
</a>
17.7.5.3 How to Minimize and Handle Deadlocks
</h4>
</div>
</div>
</div>
<p>
This section builds on the conceptual information about
deadlocks in
<a class="xref" href="innodb-deadlock-detection.html" title="17.7.5.2 Deadlock Detection">
Section 17.7.5.2, “Deadlock Detection”
</a>
. It
explains how to organize database operations to minimize
deadlocks and the subsequent error handling required in
applications.
</p>
<p>
<a class="link" href="glossary.html#glos_deadlock" title="deadlock">
Deadlocks
</a>
are a classic
problem in transactional databases, but they are not dangerous
unless they are so frequent that you cannot run certain
transactions at all. Normally, you must write your applications
so that they are always prepared to re-issue a transaction if it
gets rolled back because of a deadlock.
</p>
<p>
<code class="literal">
InnoDB
</code>
uses automatic row-level locking. You
can get deadlocks even in the case of transactions that just
insert or delete a single row. That is because these operations
are not really
<span class="quote">
“
<span class="quote">
atomic
</span>
”
</span>
; they automatically set
locks on the (possibly several) index records of the row
inserted or deleted.
</p>
<p>
You can cope with deadlocks and reduce the likelihood of their
occurrence with the following techniques:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
At any time, issue
<a class="link" href="show-engine.html" title="15.7.7.16 SHOW ENGINE Statement">
<code class="literal">
SHOW ENGINE
INNODB STATUS
</code>
</a>
to determine the cause of the most
recent deadlock. That can help you to tune your application
to avoid deadlocks.
</p>
</li>
<li class="listitem">
<p>
If frequent deadlock warnings cause concern, collect more
extensive debugging information by enabling the
<a class="link" href="innodb-parameters.html#sysvar_innodb_print_all_deadlocks">
<code class="literal">
innodb_print_all_deadlocks
</code>
</a>
variable. Information about each deadlock, not just the
latest one, is recorded in the MySQL
<a class="link" href="glossary.html#glos_error_log" title="error log">
error log
</a>
. Disable
this option when you are finished debugging.
</p>
</li>
<li class="listitem">
<p>
Always be prepared to re-issue a transaction if it fails due
to deadlock. Deadlocks are not dangerous. Just try again.
</p>
</li>
<li class="listitem">
<p>
Keep transactions small and short in duration to make them
less prone to collision.
</p>
</li>
<li class="listitem">
<p>
Commit transactions immediately after making a set of
related changes to make them less prone to collision. In
particular, do not leave an interactive
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
session open for a long time with
an uncommitted transaction.
</p>
</li>
<li class="listitem">
<p>
If you use
<a class="link" href="glossary.html#glos_locking_read" title="locking read">
locking
reads
</a>
(
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
... FOR UPDATE
</code>
</a>
or
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT ... FOR
SHARE
</code>
</a>
), try using a lower isolation level such as
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_read-committed">
<code class="literal">
READ COMMITTED
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
When modifying multiple tables within a transaction, or
different sets of rows in the same table, do those
operations in a consistent order each time. Then
transactions form well-defined queues and do not deadlock.
For example, organize database operations into functions
within your application, or call stored routines, rather
than coding multiple similar sequences of
<code class="literal">
INSERT
</code>
,
<code class="literal">
UPDATE
</code>
, and
<code class="literal">
DELETE
</code>
statements in different places.
</p>
</li>
<li class="listitem">
<p>
Add well-chosen indexes to your tables so that your queries
scan fewer index records and set fewer locks. Use
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
SELECT
</code>
</a>
to determine which indexes the MySQL server
regards as the most appropriate for your queries.
</p>
</li>
<li class="listitem">
<p>
Use less locking. If you can afford to permit a
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
to return data from an
old snapshot, do not add a
<code class="literal">
FOR UPDATE
</code>
or
<code class="literal">
FOR SHARE
</code>
clause to it. Using the
<a class="link" href="innodb-transaction-isolation-levels.html#isolevel_read-committed">
<code class="literal">
READ COMMITTED
</code>
</a>
isolation
level is good here, because each consistent read within the
same transaction reads from its own fresh snapshot.
</p>
</li>
<li class="listitem">
<p>
If nothing else helps, serialize your transactions with
table-level locks. The correct way to use
<a class="link" href="lock-tables.html" title="15.3.6 LOCK TABLES and UNLOCK TABLES Statements">
<code class="literal">
LOCK TABLES
</code>
</a>
with
transactional tables, such as
<code class="literal">
InnoDB
</code>
tables, is to begin a transaction with
<code class="literal">
SET
autocommit = 0
</code>
(not
<a class="link" href="commit.html" title="15.3.1 START TRANSACTION, COMMIT, and ROLLBACK Statements">
<code class="literal">
START
TRANSACTION
</code>
</a>
) followed by
<a class="link" href="lock-tables.html" title="15.3.6 LOCK TABLES and UNLOCK TABLES Statements">
<code class="literal">
LOCK
TABLES
</code>
</a>
, and to not call
<a class="link" href="lock-tables.html" title="15.3.6 LOCK TABLES and UNLOCK TABLES Statements">
<code class="literal">
UNLOCK
TABLES
</code>
</a>
until you commit the transaction
explicitly. For example, if you need to write to table
<code class="literal">
t1
</code>
and read from table
<code class="literal">
t2
</code>
, you can do this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa28768858"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> autocommit<span class="token operator">=</span><span class="token number">0</span><span class="token punctuation">;</span>
<span class="token keyword">LOCK</span> <span class="token keyword">TABLES</span> t1 <span class="token keyword">WRITE</span><span class="token punctuation">,</span> t2 <span class="token keyword">READ</span><span class="token punctuation">,</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">;</span>
<span class="token punctuation"></span><em class="replaceable"><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">do</span> something <span class="token keyword">with</span> <span class="token keyword">tables</span> t1 <span class="token operator">and</span> t2 here <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></em><span class="token punctuation"></span>
<span class="token keyword">COMMIT</span><span class="token punctuation">;</span>
<span class="token keyword">UNLOCK</span> <span class="token keyword">TABLES</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Table-level locks prevent concurrent updates to the table,
avoiding deadlocks at the expense of less responsiveness for
a busy system.
</p>
</li>
<li class="listitem">
<p>
Another way to serialize transactions is to create an
auxiliary
<span class="quote">
“
<span class="quote">
semaphore
</span>
”
</span>
table that contains just
a single row. Have each transaction update that row before
accessing other tables. In that way, all transactions happen
in a serial fashion. Note that the
<code class="literal">
InnoDB
</code>
instant deadlock detection algorithm also works in this
case, because the serializing lock is a row-level lock. With
MySQL table-level locks, the timeout method must be used to
resolve deadlocks.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/test-pluggable-authentication.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="test-pluggable-authentication">
</a>
8.4.1.12 Test Pluggable Authentication
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045243849488">
</a>
<a class="indexterm" name="idm46045243848384">
</a>
<a class="indexterm" name="idm46045243846896">
</a>
<a class="indexterm" name="idm46045243845808">
</a>
<p>
MySQL includes a test plugin that checks account credentials and
logs success or failure to the server error log. This is a
loadable plugin (not built in) and must be installed prior to
use.
</p>
<p>
The test plugin source code is separate from the server source,
unlike the built-in native plugin, so it can be examined as a
relatively simple example demonstrating how to write a loadable
authentication plugin.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
This plugin is intended for testing and development purposes,
and is not for use in production environments or on servers
that are exposed to public networks.
</p>
</div>
<p>
The following table shows the plugin and library file names. The
file name suffix might differ on your system. The file must be
located in the directory named by the
<a class="link" href="server-system-variables.html#sysvar_plugin_dir">
<code class="literal">
plugin_dir
</code>
</a>
system variable.
</p>
<div class="table">
<a name="idm46045243840224">
</a>
<p class="title">
<b>
Table 8.27 Plugin and Library Names for Test Authentication
</b>
</p>
<div class="table-contents">
<table summary="Names for the plugins and library file used for test password authentication.">
<colgroup>
<col style="width: 30%"/>
<col style="width: 70%"/>
</colgroup>
<thead>
<tr>
<th>
Plugin or File
</th>
<th>
Plugin or File Name
</th>
</tr>
</thead>
<tbody>
<tr>
<td>
Server-side plugin
</td>
<td>
<code class="literal">
test_plugin_server
</code>
</td>
</tr>
<tr>
<td>
Client-side plugin
</td>
<td>
<code class="literal">
auth_test_plugin
</code>
</td>
</tr>
<tr>
<td>
Library file
</td>
<td>
<code class="filename">
auth_test_plugin.so
</code>
</td>
</tr>
</tbody>
</table>
</div>
</div>
<br class="table-break"/>
<p>
The following sections provide installation and usage
information specific to test pluggable authentication:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="test-pluggable-authentication.html#test-pluggable-authentication-installation" title="Installing Test Pluggable Authentication">
Installing Test Pluggable Authentication
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="test-pluggable-authentication.html#test-pluggable-authentication-uninstallation" title="Uninstalling Test Pluggable Authentication">
Uninstalling Test Pluggable Authentication
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="test-pluggable-authentication.html#test-pluggable-authentication-usage" title="Using Test Pluggable Authentication">
Using Test Pluggable Authentication
</a>
</p>
</li>
</ul>
</div>
<p>
For general information about pluggable authentication in MySQL,
see
<a class="xref" href="pluggable-authentication.html" title="8.2.17 Pluggable Authentication">
Section 8.2.17, “Pluggable Authentication”
</a>
.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="test-pluggable-authentication-installation">
</a>
Installing Test Pluggable Authentication
</h5>
</div>
</div>
</div>
<p>
This section describes how to install the server-side test
authentication plugin. For general information about
installing plugins, see
<a class="xref" href="plugin-loading.html" title="7.6.1 Installing and Uninstalling Plugins">
Section 7.6.1, “Installing and Uninstalling Plugins”
</a>
.
</p>
<p>
To be usable by the server, the plugin library file must be
located in the MySQL plugin directory (the directory named by
the
<a class="link" href="server-system-variables.html#sysvar_plugin_dir">
<code class="literal">
plugin_dir
</code>
</a>
system
variable). If necessary, configure the plugin directory
location by setting the value of
<a class="link" href="server-system-variables.html#sysvar_plugin_dir">
<code class="literal">
plugin_dir
</code>
</a>
at server startup.
</p>
<p>
To load the plugin at server startup, use the
<a class="link" href="server-options.html#option_mysqld_plugin-load-add">
<code class="option">
--plugin-load-add
</code>
</a>
option to
name the library file that contains it. With this
plugin-loading method, the option must be given each time the
server starts. For example, put these lines in the server
<code class="filename">
my.cnf
</code>
file, adjusting the
<code class="filename">
.so
</code>
suffix for your platform as
necessary:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa93798454"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token selector">[mysqld]</span>
<span class="token constant">plugin-load-add</span><span class="token attr-value"><span class="token punctuation">=</span>auth_test_plugin.so</span></code></pre>
</div>
<p>
After modifying
<code class="filename">
my.cnf
</code>
, restart the
server to cause the new settings to take effect.
</p>
<p>
Alternatively, to load the plugin at runtime, use this
statement, adjusting the
<code class="filename">
.so
</code>
suffix for
your platform as necessary:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa11745489"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">INSTALL</span> <span class="token keyword">PLUGIN</span> test_plugin_server <span class="token keyword">SONAME</span> <span class="token string">'auth_test_plugin.so'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
<a class="link" href="install-plugin.html" title="15.7.4.4 INSTALL PLUGIN Statement">
<code class="literal">
INSTALL PLUGIN
</code>
</a>
loads the plugin
immediately, and also registers it in the
<code class="literal">
mysql.plugins
</code>
system table to cause the
server to load it for each subsequent normal startup without
the need for
<a class="link" href="server-options.html#option_mysqld_plugin-load-add">
<code class="option">
--plugin-load-add
</code>
</a>
.
</p>
<p>
To verify plugin installation, examine the Information Schema
<a class="link" href="information-schema-plugins-table.html" title="28.3.22 The INFORMATION_SCHEMA PLUGINS Table">
<code class="literal">
PLUGINS
</code>
</a>
table or use the
<a class="link" href="show-plugins.html" title="15.7.7.27 SHOW PLUGINS Statement">
<code class="literal">
SHOW PLUGINS
</code>
</a>
statement (see
<a class="xref" href="obtaining-plugin-information.html" title="7.6.2 Obtaining Server Plugin Information">
Section 7.6.2, “Obtaining Server Plugin Information”
</a>
). For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44337853"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> PLUGIN_NAME<span class="token punctuation">,</span> PLUGIN_STATUS
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span><span class="token keyword">PLUGINS</span>
<span class="token keyword">WHERE</span> PLUGIN_NAME <span class="token operator">LIKE</span> <span class="token string">'%test_plugin%'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> PLUGIN_NAME <span class="token punctuation">|</span> PLUGIN_STATUS <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> test_plugin_server <span class="token punctuation">|</span> ACTIVE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
If the plugin fails to initialize, check the server error log
for diagnostic messages.
</p>
<p>
To associate MySQL accounts with the test plugin, see
<a class="xref" href="test-pluggable-authentication.html#test-pluggable-authentication-usage" title="Using Test Pluggable Authentication">
Using Test Pluggable Authentication
</a>
.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="test-pluggable-authentication-uninstallation">
</a>
Uninstalling Test Pluggable Authentication
</h5>
</div>
</div>
</div>
<p>
The method used to uninstall the test authentication plugin
depends on how you installed it:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If you installed the plugin at server startup using a
<a class="link" href="server-options.html#option_mysqld_plugin-load-add">
<code class="option">
--plugin-load-add
</code>
</a>
option,
restart the server without the option.
</p>
</li>
<li class="listitem">
<p>
If you installed the plugin at runtime using an
<a class="link" href="install-plugin.html" title="15.7.4.4 INSTALL PLUGIN Statement">
<code class="literal">
INSTALL PLUGIN
</code>
</a>
statement,
it remains installed across server restarts. To uninstall
it, use
<a class="link" href="uninstall-plugin.html" title="15.7.4.6 UNINSTALL PLUGIN Statement">
<code class="literal">
UNINSTALL PLUGIN
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa9991986"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">UNINSTALL</span> <span class="token keyword">PLUGIN</span> test_plugin_server<span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="test-pluggable-authentication-usage">
</a>
Using Test Pluggable Authentication
</h5>
</div>
</div>
</div>
<p>
To use the test authentication plugin, create an account and
name that plugin in the
<code class="literal">
IDENTIFIED WITH
</code>
clause:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa44256260"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> <span class="token string">'testuser'</span>@<span class="token string">'localhost'</span>
<span class="token keyword">IDENTIFIED</span> <span class="token keyword">WITH</span> test_plugin_server
<span class="token keyword">BY</span> <span class="token string">'<em class="replaceable">testpassword</em>'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The test authentication plugin also requires creating a proxy
user as follows:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa91352052"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">USER</span> testpassword<span class="token variable">@localhost</span><span class="token punctuation">;</span>
<span class="token keyword">GRANT</span> <span class="token keyword">PROXY</span> <span class="token keyword">ON</span> testpassword<span class="token variable">@localhost</span> <span class="token keyword">TO</span> testuser<span class="token variable">@localhost</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Then provide the
<a class="link" href="connection-options.html#option_general_user">
<code class="option">
--user
</code>
</a>
and
<a class="link" href="connection-options.html#option_general_password">
<code class="option">
--password
</code>
</a>
options for that
account when you connect to the server. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa55961003"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">mysql</span> <span class="token constant">--user</span><span class="token attr-value"><span class="token punctuation">=</span>testuser</span> <span class="token property">--password</span>
Enter password<span class="token punctuation">:</span> <em class="replaceable">testpassword</em></code></pre>
</div>
<p>
The plugin fetches the password as received from the client
and compares it with the value stored in the
<code class="literal">
authentication_string
</code>
column of the account
row in the
<code class="literal">
mysql.user
</code>
system table. If the
two values match, the plugin returns the
<code class="literal">
authentication_string
</code>
value as the new
effective user ID.
</p>
<p>
You can look in the server error log for a message indicating
whether authentication succeeded (notice that the password is
reported as the
<span class="quote">
“
<span class="quote">
user
</span>
”
</span>
):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa65096543"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">[Note] Plugin test_plugin_server reported:
'successfully authenticated user <em class="replaceable">testpassword</em>'</code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/innodb-compression-usage.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="innodb-compression-usage">
</a>
17.9.1.2 Creating Compressed Tables
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045161724704">
</a>
<a class="indexterm" name="idm46045161723216">
</a>
<a class="indexterm" name="idm46045161722144">
</a>
<a class="indexterm" name="idm46045161720656">
</a>
<a class="indexterm" name="idm46045161719584">
</a>
<p>
Compressed tables can be created in
<a class="link" href="glossary.html#glos_file_per_table" title="file-per-table">
file-per-table
</a>
tablespaces or in
<a class="link" href="glossary.html#glos_general_tablespace" title="general tablespace">
general
tablespaces
</a>
. Table compression is not available for the
InnoDB
<a class="link" href="glossary.html#glos_system_tablespace" title="system tablespace">
system
tablespace
</a>
. The system tablespace (space 0, the
<a class="link" href="glossary.html#glos_ibd_file" title=".ibd file">
.ibdata files
</a>
) can contain
user-created tables, but it also contains internal system data,
which is never compressed. Thus, compression applies only to
tables (and indexes) stored in file-per-table or general
tablespaces.
</p>
<h5>
<a name="idm46045161713952">
</a>
Creating a Compressed Table in File-Per-Table Tablespace
</h5>
<p>
To create a compressed table in a file-per-table tablespace,
<a class="link" href="innodb-parameters.html#sysvar_innodb_file_per_table">
<code class="literal">
innodb_file_per_table
</code>
</a>
must be
enabled (the default). You can set this parameter in the MySQL
configuration file (
<code class="filename">
my.cnf
</code>
or
<code class="filename">
my.ini
</code>
) or dynamically, using a
<a class="link" href="set-variable.html" title="15.7.6.1 SET Syntax for Variable Assignment">
<code class="literal">
SET
</code>
</a>
statement.
</p>
<p>
After the
<a class="link" href="innodb-parameters.html#sysvar_innodb_file_per_table">
<code class="literal">
innodb_file_per_table
</code>
</a>
option is configured, specify the
<code class="literal">
ROW_FORMAT=COMPRESSED
</code>
clause or
<code class="literal">
KEY_BLOCK_SIZE
</code>
clause, or both, in a
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
or
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
statement to create a
compressed table in a file-per-table tablespace.
</p>
<p>
For example, you might use the following statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa65922435"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> innodb_file_per_table<span class="token operator">=</span><span class="token number">1</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1
<span class="token punctuation">(</span>c1 <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">)</span>
<span class="token keyword">ROW_FORMAT</span><span class="token operator">=</span><span class="token keyword">COMPRESSED</span>
<span class="token keyword">KEY_BLOCK_SIZE</span><span class="token operator">=</span><span class="token number">8</span><span class="token punctuation">;</span></code></pre>
</div>
<h5>
<a name="idm46045161701472">
</a>
Creating a Compressed Table in a General Tablespace
</h5>
<p>
To create a compressed table in a general tablespace,
<code class="literal">
FILE_BLOCK_SIZE
</code>
must be defined for the
general tablespace, which is specified when the tablespace is
created. The
<code class="literal">
FILE_BLOCK_SIZE
</code>
value must be a
valid compressed page size in relation to the
<a class="link" href="innodb-parameters.html#sysvar_innodb_page_size">
<code class="literal">
innodb_page_size
</code>
</a>
value, and the
page size of the compressed table, defined by the
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
or
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
<code class="literal">
KEY_BLOCK_SIZE
</code>
clause, must be equal to
<code class="literal">
FILE_BLOCK_SIZE/1024
</code>
. For example, if
<a class="link" href="innodb-parameters.html#sysvar_innodb_page_size">
<code class="literal">
innodb_page_size=16384
</code>
</a>
and
<code class="literal">
FILE_BLOCK_SIZE=8192
</code>
, the
<code class="literal">
KEY_BLOCK_SIZE
</code>
of the table must be 8. For
more information, see
<a class="xref" href="general-tablespaces.html" title="17.6.3.3 General Tablespaces">
Section 17.6.3.3, “General Tablespaces”
</a>
.
</p>
<p>
The following example demonstrates creating a general tablespace
and adding a compressed table. The example assumes a default
<a class="link" href="innodb-parameters.html#sysvar_innodb_page_size">
<code class="literal">
innodb_page_size
</code>
</a>
of 16K. The
<code class="literal">
FILE_BLOCK_SIZE
</code>
of 8192 requires that the
compressed table have a
<code class="literal">
KEY_BLOCK_SIZE
</code>
of 8.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa5060560"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLESPACE</span> <span class="token punctuation">`</span>ts2<span class="token punctuation">`</span> <span class="token keyword">ADD</span> <span class="token keyword">DATAFILE</span> <span class="token string">'ts2.ibd'</span> <span class="token keyword">FILE_BLOCK_SIZE</span> <span class="token operator">=</span> <span class="token number">8192</span> <span class="token keyword">Engine</span><span class="token operator">=</span>InnoDB<span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t4 <span class="token punctuation">(</span>c1 <span class="token datatype">INT</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span><span class="token punctuation">)</span> <span class="token keyword">TABLESPACE</span> ts2 <span class="token keyword">ROW_FORMAT</span><span class="token operator">=</span><span class="token keyword">COMPRESSED</span> <span class="token keyword">KEY_BLOCK_SIZE</span><span class="token operator">=</span><span class="token number">8</span><span class="token punctuation">;</span></code></pre>
</div>
<h5>
<a name="idm46045161684320">
</a>
Notes
</h5>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
As of MySQL 8.4, the tablespace file for a
compressed table is created using the physical page size
instead of the
<code class="literal">
InnoDB
</code>
page size, which
makes the initial size of a tablespace file for an empty
compressed table smaller than in previous MySQL releases.
</p>
</li>
<li class="listitem">
<p>
If you specify
<code class="literal">
ROW_FORMAT=COMPRESSED
</code>
, you
can omit
<code class="literal">
KEY_BLOCK_SIZE
</code>
; the
<code class="literal">
KEY_BLOCK_SIZE
</code>
setting defaults to half
the
<a class="link" href="innodb-parameters.html#sysvar_innodb_page_size">
<code class="literal">
innodb_page_size
</code>
</a>
value.
</p>
</li>
<li class="listitem">
<p>
If you specify a valid
<code class="literal">
KEY_BLOCK_SIZE
</code>
value, you can omit
<code class="literal">
ROW_FORMAT=COMPRESSED
</code>
; compression is
enabled automatically.
</p>
</li>
<li class="listitem">
<p>
To determine the best value for
<code class="literal">
KEY_BLOCK_SIZE,
</code>
typically you create
several copies of the same table with different values for
this clause, then measure the size of the resulting
<code class="filename">
.ibd
</code>
files and see how well each
performs with a realistic
<a class="link" href="glossary.html#glos_workload" title="workload">
workload
</a>
. For general
tablespaces, keep in mind that dropping a table does not
reduce the size of the general tablespace
<code class="filename">
.ibd
</code>
file, nor does it return disk
space to the operating system. For more information, see
<a class="xref" href="general-tablespaces.html" title="17.6.3.3 General Tablespaces">
Section 17.6.3.3, “General Tablespaces”
</a>
.
</p>
</li>
<li class="listitem">
<p>
The
<code class="literal">
KEY_BLOCK_SIZE
</code>
value is treated as a
hint; a different size could be used by
<code class="literal">
InnoDB
</code>
if necessary. For file-per-table
tablespaces, the
<code class="literal">
KEY_BLOCK_SIZE
</code>
can only
be less than or equal to the
<a class="link" href="innodb-parameters.html#sysvar_innodb_page_size">
<code class="literal">
innodb_page_size
</code>
</a>
value. If
you specify a value greater than the
<a class="link" href="innodb-parameters.html#sysvar_innodb_page_size">
<code class="literal">
innodb_page_size
</code>
</a>
value, the
specified value is ignored, a warning is issued, and
<code class="literal">
KEY_BLOCK_SIZE
</code>
is set to half of the
<a class="link" href="innodb-parameters.html#sysvar_innodb_page_size">
<code class="literal">
innodb_page_size
</code>
</a>
value. If
<code class="literal">
innodb_strict_mode=ON
</code>
, specifying an
invalid
<code class="literal">
KEY_BLOCK_SIZE
</code>
value returns an
error. For general tablespaces, valid
<code class="literal">
KEY_BLOCK_SIZE
</code>
values depend on the
<code class="literal">
FILE_BLOCK_SIZE
</code>
setting of the
tablespace. For more information, see
<a class="xref" href="general-tablespaces.html" title="17.6.3.3 General Tablespaces">
Section 17.6.3.3, “General Tablespaces”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
InnoDB
</code>
supports 32KB and 64KB page sizes
but these page sizes do not support compression. For more
information, refer to the
<a class="link" href="innodb-parameters.html#sysvar_innodb_page_size">
<code class="literal">
innodb_page_size
</code>
</a>
documentation.
</p>
</li>
<li class="listitem">
<p>
The default uncompressed size of
<code class="literal">
InnoDB
</code>
data
<a class="link" href="glossary.html#glos_page" title="page">
pages
</a>
is 16KB.
Depending on the combination of option values, MySQL uses a
page size of 1KB, 2KB, 4KB, 8KB, or 16KB for the tablespace
data file (
<code class="filename">
.ibd
</code>
file). The actual
compression algorithm is not affected by the
<code class="literal">
KEY_BLOCK_SIZE
</code>
value; the value
determines how large each compressed chunk is, which in turn
affects how many rows can be packed into each compressed
page.
</p>
</li>
<li class="listitem">
<p>
When creating a compressed table in a file-per-table
tablespace, setting
<code class="literal">
KEY_BLOCK_SIZE
</code>
equal
to the
<code class="literal">
InnoDB
</code>
<a class="link" href="glossary.html#glos_page_size" title="page size">
page size
</a>
does not
typically result in much compression. For example, setting
<code class="literal">
KEY_BLOCK_SIZE=16
</code>
typically would not
result in much compression, since the normal
<code class="literal">
InnoDB
</code>
page size is 16KB. This setting
may still be useful for tables with many long
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
,
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
or
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
columns, because such
values often do compress well, and might therefore require
fewer
<a class="link" href="glossary.html#glos_overflow_page" title="overflow page">
overflow
pages
</a>
as described in
<a class="xref" href="innodb-compression-internals.html" title="17.9.1.5 How Compression Works for InnoDB Tables">
Section 17.9.1.5, “How Compression Works for InnoDB Tables”
</a>
. For general
tablespaces, a
<code class="literal">
KEY_BLOCK_SIZE
</code>
value equal
to the
<code class="literal">
InnoDB
</code>
page size is not permitted.
For more information, see
<a class="xref" href="general-tablespaces.html" title="17.6.3.3 General Tablespaces">
Section 17.6.3.3, “General Tablespaces”
</a>
.
</p>
</li>
<li class="listitem">
<p>
All indexes of a table (including the
<a class="link" href="glossary.html#glos_clustered_index" title="clustered index">
clustered index
</a>
)
are compressed using the same page size, as specified in the
<code class="literal">
CREATE TABLE
</code>
or
<code class="literal">
ALTER
TABLE
</code>
statement. Table attributes such as
<code class="literal">
ROW_FORMAT
</code>
and
<code class="literal">
KEY_BLOCK_SIZE
</code>
are not part of the
<code class="literal">
CREATE INDEX
</code>
syntax for
<code class="literal">
InnoDB
</code>
tables, and are ignored if they
are specified (although, if specified, they appear in the
output of the
<a class="link" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement">
<code class="literal">
SHOW CREATE
TABLE
</code>
</a>
statement).
</p>
</li>
<li class="listitem">
<p>
For performance-related configuration options, see
<a class="xref" href="innodb-compression-tuning.html" title="17.9.1.3 Tuning Compression for InnoDB Tables">
Section 17.9.1.3, “Tuning Compression for InnoDB Tables”
</a>
.
</p>
</li>
</ul>
</div>
<h5>
<a name="idm46045161629520">
</a>
Restrictions on Compressed Tables
</h5>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Compressed tables cannot be stored in the
<code class="literal">
InnoDB
</code>
system tablespace.
</p>
</li>
<li class="listitem">
<p>
General tablespaces can contain multiple tables, but
compressed and uncompressed tables cannot coexist within the
same general tablespace.
</p>
</li>
<li class="listitem">
<p>
Compression applies to an entire table and all its
associated indexes, not to individual rows, despite the
clause name
<code class="literal">
ROW_FORMAT
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
InnoDB
</code>
does not support compressed
temporary tables. When
<a class="link" href="innodb-parameters.html#sysvar_innodb_strict_mode">
<code class="literal">
innodb_strict_mode
</code>
</a>
is
enabled (the default),
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE
TEMPORARY TABLE
</code>
</a>
returns errors if
<code class="literal">
ROW_FORMAT=COMPRESSED
</code>
or
<code class="literal">
KEY_BLOCK_SIZE
</code>
is specified. If
<a class="link" href="innodb-parameters.html#sysvar_innodb_strict_mode">
<code class="literal">
innodb_strict_mode
</code>
</a>
is
disabled, warnings are issued and the temporary table is
created using a non-compressed row format. The same
restrictions apply to
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
operations on temporary tables.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/csv-storage-engine.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="csv-storage-engine">
</a>
18.4 The CSV Storage Engine
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="se-csv-repair.html">
18.4.1 Repairing and Checking CSV Tables
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="se-csv-limitations.html">
18.4.2 CSV Limitations
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045147736576">
</a>
<a class="indexterm" name="idm46045147735504">
</a>
<p>
The
<code class="literal">
CSV
</code>
storage engine stores data in text files
using comma-separated values format.
</p>
<p>
The
<code class="literal">
CSV
</code>
storage engine is always compiled into
the MySQL server.
</p>
<p>
To examine the source for the
<code class="literal">
CSV
</code>
engine, look in
the
<code class="filename">
storage/csv
</code>
directory of a MySQL source
distribution.
</p>
<p>
When you create a
<code class="literal">
CSV
</code>
table, the server creates a
plain text data file having a name that begins with the table name
and has a
<code class="filename">
.CSV
</code>
extension. When you store data
into the table, the storage engine saves it into the data file in
comma-separated values format.
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa33649344"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> test <span class="token punctuation">(</span>i <span class="token datatype">INT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">,</span> c <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">10</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">)</span>
<span class="token prompt"> -></span> <span class="token keyword">ENGINE</span> <span class="token operator">=</span> CSV<span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.06 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> test
<span class="token prompt"> -></span> <span class="token keyword">VALUES</span> <span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token string">'record one'</span><span class="token punctuation">)</span><span class="token punctuation">,</span> <span class="token keyword">ROW</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token string">'record two'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 2 rows affected (0.05 sec)</span>
<span class="token output">Records: 2 Duplicates: 0 Warnings: 0</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> test<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> i <span class="token punctuation">|</span> c <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> record one <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> record two <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">2 rows in set (0.00 sec)</span></code></pre>
</div>
<p>
Creating a
<code class="literal">
CSV
</code>
table also creates a corresponding
metafile that stores the state of the table and the number of rows
that exist in the table. The name of this file is the same as the
name of the table with the extension
<code class="filename">
CSM
</code>
.
</p>
<p>
If you examine the
<code class="filename">
test.CSV
</code>
file in the
database directory created by executing the preceding statements,
its contents should look like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa79140145"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">"1","record one"
"2","record two"</code></pre>
</div>
<p>
This format can be read, and even written, by spreadsheet
applications such as Microsoft Excel.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/performance-schema-build-configuration.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="performance-schema-build-configuration">
</a>
29.2 Performance Schema Build Configuration
</h2>
</div>
</div>
</div>
<p>
The Performance Schema is mandatory and always compiled in. It is
possible to exclude certain parts of the Performance Schema
instrumentation. For example, to exclude stage and statement
instrumentation, do this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa33568553"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">$> </span><span class="token command">cmake</span> <span class="token punctuation">.</span> \
<span class="token constant">-DDISABLE_PSI_STAGE</span><span class="token attr-value"><span class="token punctuation">=</span>1</span> \
<span class="token constant">-DDISABLE_PSI_STATEMENT</span><span class="token attr-value"><span class="token punctuation">=</span>1</span></code></pre>
</div>
<p>
For more information, see the descriptions of the
<code class="literal">
DISABLE_PSI_
<em class="replaceable">
<code>
XXX
</code>
</em>
</code>
<span class="command">
<strong>
CMake
</strong>
</span>
options in
<a class="xref" href="source-configuration-options.html" title="2.8.7 MySQL Source-Configuration Options">
Section 2.8.7, “MySQL Source-Configuration Options”
</a>
.
</p>
<p>
If you install MySQL over a previous installation that was
configured without the Performance Schema (or with an older
version of the Performance Schema that has missing or out-of-date
tables). One indication of this issue is the presence of messages
such as the following in the error log:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa56732322"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">[ERROR] Native table 'performance_schema'.'events_waits_history'
has the wrong structure
[ERROR] Native table 'performance_schema'.'events_waits_history_long'
has the wrong structure
...</code></pre>
</div>
<p>
To correct that problem, perform the MySQL upgrade procedure. See
<a class="xref" href="upgrading.html" title="Chapter 3 Upgrading MySQL">
Chapter 3,
<i>
Upgrading MySQL
</i>
</a>
.
</p>
<p>
Because the Performance Schema is configured into the server at
build time, a row for
<a class="link" href="performance-schema.html" title="Chapter 29 MySQL Performance Schema">
<code class="literal">
PERFORMANCE_SCHEMA
</code>
</a>
appears in the
output from
<a class="link" href="show-engines.html" title="15.7.7.17 SHOW ENGINES Statement">
<code class="literal">
SHOW ENGINES
</code>
</a>
. This
means that the Performance Schema is available, not that it is
enabled. To enable it, you must do so at server startup, as
described in the next section.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-oci-marketplace-deploy.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="mysql-oci-marketplace-deploy">
</a>
34.2 Deploying MySQL EE on Oracle Cloud Infrastructure
</h2>
</div>
</div>
</div>
<p>
To deploy MySQL EE on Oracle Cloud Infrastructure, do the
following:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Open the OCI Marketplace and search for
<span class="guilabel">
MySQL
</span>
.
</p>
<p>
The
<span class="guilabel">
MySQL
</span>
listings are displayed.
</p>
</li>
<li class="listitem">
<p>
Select
<span class="guilabel">
MySQL Enterprise Edition
</span>
.
</p>
<p>
The
<span class="guilabel">
MySQL Enterprise Edition
</span>
overview is displaed.
</p>
</li>
<li class="listitem">
<p>
Click
<span class="guilabel">
Launch Instance
</span>
to begin the
application launch process.
</p>
<p>
The
<span class="guilabel">
Create Compute Instance
</span>
dialog is
displayed.
</p>
<p>
See
<a class="ulink" href="https://docs.cloud.oracle.com/iaas/Content/Compute/Tasks/launchinginstance.htm" target="_blank">
To
create a Linux instance
</a>
for information on how to
complete the fields.
</p>
</li>
</ol>
</div>
<p>
By default, the MySQL server listens on port 3306 and is
configured with a single user, root.
</p>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
When the deployment is complete, and the MySQL server is
started, you must connect to the compute instance and retrieve
the default root password which was written to the MySQL log
file.
</p>
<p>
See
<a class="xref" href="mysql-oci-marketplace-connecting.html#mysql-oci-marketplace-connecting-ssh" title="Connecting with SSH">
Connecting with SSH
</a>
for
more information.
</p>
</div>
<p>
The following MySQL software is installed:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
MySQL Server EE
</p>
</li>
<li class="listitem">
<p>
MySQL Enterprise Backup
</p>
</li>
<li class="listitem">
<p>
MySQL Shell
</p>
</li>
<li class="listitem">
<p>
MySQL Router
</p>
</li>
</ul>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h3 class="title">
<a name="idm46045060103392">
</a>
MySQL Configuration
</h3>
</div>
</div>
</div>
<p>
For security, the following are enabled:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
SELinux: for more information, see
<a class="ulink" href="https://docs.oracle.com/en/operating-systems/oracle-linux/7/admin/ol7-s1-syssec.html" target="_blank">
Configuring
and Using SELinux
</a>
</p>
</li>
<li class="listitem">
<p>
<code class="filename">
firewalld
</code>
: for more information, see
<a class="ulink" href="https://docs.oracle.com/en/operating-systems/oracle-linux/7/security/ol7-implement-sec.html#ol7-firewalld-cfg" target="_blank">
Controlling
the firewalld Firewall Service
</a>
</p>
</li>
</ul>
</div>
<p>
The following MySQL plugins are enabled:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="filename">
thread_pool
</code>
</p>
</li>
<li class="listitem">
<p>
<code class="filename">
validate_password
</code>
</p>
</li>
</ul>
</div>
<p>
On startup, the following occurs:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
MySQL Server reads
<code class="filename">
/etc/my.cnf
</code>
and all
files named
<code class="filename">
<em class="replaceable">
<code>
*
</code>
</em>
.cnf
</code>
in
<code class="filename">
/etc/my.cnf.d/
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="filename">
/etc/my.cnf.d/perf-tuning.cnf
</code>
is
created by
<code class="filename">
/usr/bin/mkcnf
</code>
based on the
selected OCI shape.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
To disable this mechanism, remove
<code class="filename">
/etc/systemd/system/mysqld.service.d/perf-tuning.conf
</code>
.
</p>
</div>
<p>
Performance tuning is configured for the following shapes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
VM.Standard2.1
</p>
</li>
<li class="listitem">
<p>
VM.Standard2.2
</p>
</li>
<li class="listitem">
<p>
VM.Standard2.4
</p>
</li>
<li class="listitem">
<p>
VM.Standard2.8
</p>
</li>
<li class="listitem">
<p>
VM.Standard2.16
</p>
</li>
<li class="listitem">
<p>
VM.Standard2.24
</p>
</li>
<li class="listitem">
<p>
VM.Standard.E2.1
</p>
</li>
<li class="listitem">
<p>
VM.Standard.E2.2
</p>
</li>
<li class="listitem">
<p>
VM.Standard.E2.4
</p>
</li>
<li class="listitem">
<p>
VM.Standard.E2.8
</p>
</li>
<li class="listitem">
<p>
VM.Standard.E3.Flex
</p>
</li>
<li class="listitem">
<p>
VM.Standard.E4.Flex
</p>
</li>
<li class="listitem">
<p>
BM.Standard2.52
</p>
</li>
</ul>
</div>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
For all other shapes, the tuning for VM.Standard2.1 is
used.
</p>
</div>
</li>
</ul>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/identifiers.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="identifiers">
</a>
11.2 Schema Object Names
</h2>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="identifier-length.html">
11.2.1 Identifier Length Limits
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="identifier-qualifiers.html">
11.2.2 Identifier Qualifiers
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="identifier-case-sensitivity.html">
11.2.3 Identifier Case Sensitivity
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="identifier-mapping.html">
11.2.4 Mapping of Identifiers to File Names
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="function-resolution.html">
11.2.5 Function Name Parsing and Resolution
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045220079968">
</a>
<a class="indexterm" name="idm46045220078896">
</a>
<a class="indexterm" name="idm46045220077824">
</a>
<a class="indexterm" name="idm46045220076752">
</a>
<a class="indexterm" name="idm46045220075264">
</a>
<a class="indexterm" name="idm46045220073776">
</a>
<a class="indexterm" name="idm46045220072288">
</a>
<a class="indexterm" name="idm46045220070800">
</a>
<a class="indexterm" name="idm46045220069312">
</a>
<p>
Certain objects within MySQL, including database, table, index,
column, alias, view, stored procedure, partition, tablespace,
resource group and other object names are known as identifiers.
This section describes the permissible syntax for identifiers in
MySQL.
<a class="xref" href="identifier-length.html" title="11.2.1 Identifier Length Limits">
Section 11.2.1, “Identifier Length Limits”
</a>
, indicates the maximum
length of each type of identifier.
<a class="xref" href="identifier-case-sensitivity.html" title="11.2.3 Identifier Case Sensitivity">
Section 11.2.3, “Identifier Case Sensitivity”
</a>
, describes which
types of identifiers are case-sensitive and under what conditions.
</p>
<a class="indexterm" name="idm46045220065408">
</a>
<a class="indexterm" name="idm46045220063920">
</a>
<a class="indexterm" name="idm46045220062848">
</a>
<a class="indexterm" name="idm46045220061808">
</a>
<p>
An identifier may be quoted or unquoted. If an identifier contains
special characters or is a reserved word, you
<span class="emphasis">
<em>
must
</em>
</span>
quote it whenever you refer to it.
(Exception: A reserved word that follows a period in a qualified
name must be an identifier, so it need not be quoted.) Reserved
words are listed at
<a class="xref" href="keywords.html" title="11.3 Keywords and Reserved Words">
Section 11.3, “Keywords and Reserved Words”
</a>
.
</p>
<p>
Internally, identifiers are converted to and are stored as Unicode
(UTF-8). The permissible Unicode characters in identifiers are
those in the Basic Multilingual Plane (BMP). Supplementary
characters are not permitted. Identifiers thus may contain these
characters:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Permitted characters in unquoted identifiers:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
ASCII: [0-9,a-z,A-Z$_] (basic Latin letters, digits 0-9,
dollar, underscore)
</p>
</li>
<li class="listitem">
<p>
Extended: U+0080 .. U+FFFF
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Permitted characters in quoted identifiers include the full
Unicode Basic Multilingual Plane (BMP), except U+0000:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
ASCII: U+0001 .. U+007F
</p>
</li>
<li class="listitem">
<p>
Extended: U+0080 .. U+FFFF
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
ASCII NUL (U+0000) and supplementary characters (U+10000 and
higher) are not permitted in quoted or unquoted identifiers.
</p>
</li>
<li class="listitem">
<p>
Identifiers may begin with a digit but unless quoted may not
consist solely of digits.
</p>
</li>
<li class="listitem">
<p>
Database, table, and column names cannot end with space
characters.
</p>
</li>
<li class="listitem">
<p>
Use of the dollar sign as the first character in the unquoted
name of a database, table, view, column, stored program, or
alias is deprecated, including such names used with qualifiers
(see
<a class="xref" href="identifier-qualifiers.html" title="11.2.2 Identifier Qualifiers">
Section 11.2.2, “Identifier Qualifiers”
</a>
). An unquoted
identifier beginning with a dollar sign cannot contain any
additional dollar sign characters. Otherwise, the leading
dollar sign is permitted but triggers a deprecation warning.
</p>
<p>
The dollar sign can still be used as the leading character of
such an identifier without producing the warning, when it is
quoted according to the rules given later in this section.
</p>
</li>
</ul>
</div>
<p>
The identifier quote character is the backtick
(
<code class="literal">
`
</code>
):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa37468240"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> <span class="token punctuation">`</span><span class="token keyword">select</span><span class="token punctuation">`</span> <span class="token keyword">WHERE</span> <span class="token punctuation">`</span><span class="token keyword">select</span><span class="token punctuation">`</span><span class="token punctuation">.</span>id <span class="token operator">></span> <span class="token number">100</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If the
<a class="link" href="sql-mode.html#sqlmode_ansi_quotes">
<code class="literal">
ANSI_QUOTES
</code>
</a>
SQL mode is
enabled, it is also permissible to quote identifiers within double
quotation marks:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa21759660"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> <span class="token string">"test"</span> <span class="token punctuation">(</span>col <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">ERROR 1064<span class="token punctuation">:</span> You have an error in your SQL syntax...</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> sql_mode<span class="token operator">=</span><span class="token string">'ANSI_QUOTES'</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> <span class="token string">"test"</span> <span class="token punctuation">(</span>col <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output">Query OK, 0 rows affected (0.00 sec)</span></code></pre>
</div>
<p>
The
<a class="link" href="sql-mode.html#sqlmode_ansi_quotes">
<code class="literal">
ANSI_QUOTES
</code>
</a>
mode causes the
server to interpret double-quoted strings as identifiers.
Consequently, when this mode is enabled, string literals must be
enclosed within single quotation marks. They cannot be enclosed
within double quotation marks. The server SQL mode is controlled
as described in
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
.
</p>
<p>
Identifier quote characters can be included within an identifier
if you quote the identifier. If the character to be included
within the identifier is the same as that used to quote the
identifier itself, then you need to double the character. The
following statement creates a table named
<code class="literal">
a`b
</code>
that contains a column named
<code class="literal">
c"d
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa95046516"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>a<span class="token punctuation">`</span><span class="token punctuation">`</span>b<span class="token punctuation">`</span> <span class="token punctuation">(</span><span class="token punctuation">`</span>c"d<span class="token punctuation">`</span> <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<a class="indexterm" name="idm46045220032272">
</a>
<a class="indexterm" name="idm46045220030784">
</a>
<p>
In the select list of a query, a quoted column alias can be
specified using identifier or string quoting characters:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa65397435"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token number">1</span> <span class="token keyword">AS</span> <span class="token punctuation">`</span><span class="token keyword">one</span><span class="token punctuation">`</span><span class="token punctuation">,</span> <span class="token number">2</span> <span class="token keyword">AS</span> <span class="token string">'two'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> one <span class="token punctuation">|</span> two <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Elsewhere in the statement, quoted references to the alias must
use identifier quoting or the reference is treated as a string
literal.
</p>
<p>
It is recommended that you do not use names that begin with
<code class="literal">
<em class="replaceable">
<code>
M
</code>
</em>
e
</code>
or
<code class="literal">
<em class="replaceable">
<code>
M
</code>
</em>
e
<em class="replaceable">
<code>
N
</code>
</em>
</code>
,
where
<em class="replaceable">
<code>
M
</code>
</em>
and
<em class="replaceable">
<code>
N
</code>
</em>
are integers. For example, avoid
using
<code class="literal">
1e
</code>
as an identifier, because an
expression such as
<code class="literal">
1e+3
</code>
is ambiguous. Depending
on context, it might be interpreted as the expression
<code class="literal">
1e
+ 3
</code>
or as the number
<code class="literal">
1e+3
</code>
.
</p>
<p>
Be careful when using
<a class="link" href="encryption-functions.html#function_md5">
<code class="literal">
MD5()
</code>
</a>
to
produce table names because it can produce names in illegal or
ambiguous formats such as those just described.
</p>
<p>
It is also recommended that you do not use column names that begin
with
<code class="literal">
!hidden!
</code>
to ensure that new names do not
collide with names used by existing hidden columns for functional
indexes.
</p>
<p>
A user variable cannot be used directly in an SQL statement as an
identifier or as part of an identifier. See
<a class="xref" href="user-variables.html" title="11.4 User-Defined Variables">
Section 11.4, “User-Defined Variables”
</a>
, for more information and
examples of workarounds.
</p>
<p>
Special characters in database and table names are encoded in the
corresponding file system names as described in
<a class="xref" href="identifier-mapping.html" title="11.2.4 Mapping of Identifiers to File Names">
Section 11.2.4, “Mapping of Identifiers to File Names”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/group-replication-enterprise-backup.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="group-replication-enterprise-backup">
</a>
20.5.6 Using MySQL Enterprise Backup with Group Replication
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045132831264">
</a>
<a class="indexterm" name="idm46045132829776">
</a>
<p>
<a class="link" href="mysql-enterprise-backup.html" title="32.1 MySQL Enterprise Backup Overview">
MySQL Enterprise Backup
</a>
is a
commercially-licensed backup utility for MySQL Server, available
with
<a class="ulink" href="https://www.mysql.com/products/enterprise/" target="_blank">
MySQL Enterprise Edition
</a>
.
This section explains how to back up and subsequently restore a
Group Replication member using MySQL Enterprise Backup. The same technique can be
used to quickly add a new member to a group.
</p>
<h4>
<a name="idm46045132826080">
</a>
Backing up a Group Replication Member Using MySQL Enterprise Backup
</h4>
<p>
Backing up a Group Replication member is similar to backing up a
stand-alone MySQL instance. The following instructions assume that
you are already familiar with how to use MySQL Enterprise Backup to perform a
backup; if that is not the case, please review
<a class="ulink" href="/doc/mysql-enterprise-backup/8.4/en/backing-up.html" target="_top">
Backing Up a Database Server
</a>
. Also note the requirements described
in
<a class="ulink" href="/doc/mysql-enterprise-backup/8.4/en/mysqlbackup.privileges.html" target="_top">
Grant MySQL Privileges to Backup Administrator
</a>
and
<a class="ulink" href="/doc/mysql-enterprise-backup/8.4/en/meb-group-replication.html" target="_top">
Using MySQL Enterprise Backup with Group Replication
</a>
.
</p>
<p>
Consider the following group with three members,
<code class="literal">
s1
</code>
,
<code class="literal">
s2
</code>
, and
<code class="literal">
s3
</code>
, running on hosts with the same names:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa10563960"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> member_host<span class="token punctuation">,</span> member_port<span class="token punctuation">,</span> member_state <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> member_host <span class="token punctuation">|</span> member_port <span class="token punctuation">|</span> member_state <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> s1 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> s2 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> s3 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
Using MySQL Enterprise Backup, create a backup of
<code class="literal">
s2
</code>
by issuing
on its host, for example, the following command:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa55389885"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">s2> mysqlbackup <span class="token constant">--defaults-file</span><span class="token attr-value"><span class="token punctuation">=</span>/etc/my.cnf</span> <span class="token constant">--backup-image</span><span class="token attr-value"><span class="token punctuation">=</span>/backups/my.mbi_`date</span> +%d%m_%H%M` \
<span class="token constant">--backup-dir</span><span class="token attr-value"><span class="token punctuation">=</span>/backups/backup_`date</span> +%d%m_%H%M` <span class="token constant">--user</span><span class="token attr-value"><span class="token punctuation">=</span>root</span> <span class="token property">-p</span> \
<span class="token constant">--host</span><span class="token attr-value"><span class="token punctuation">=</span>127.0.0.1</span> backup-to-image</code></pre>
</div>
<h4>
<a name="group-replication-restore-failed-member">
</a>
Restoring a Failed Member
</h4>
<p>
Assume one of the members (
<code class="literal">
s3
</code>
in the following
example) is irreconcilably corrupted. The most recent backup of
group member
<code class="literal">
s2
</code>
can be used to restore
<code class="literal">
s3
</code>
. Here are the steps for performing the
restore:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
<span class="emphasis">
<em>
Copy the backup of s2 onto the host for
s3.
</em>
</span>
The exact way to copy the backup depends on the
operating system and tools available to you. In this example,
we assume the hosts are both Linux servers and use SCP to copy
the files between them:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa37970269"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">s2/backups> scp my<span class="token punctuation">.</span>mbi_2206_1429 s3<span class="token punctuation">:</span>/backups</code></pre>
</div>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Restore the backup.
</em>
</span>
Connect to the target
host (the host for
<code class="literal">
s3
</code>
in this case), and
restore the backup using MySQL Enterprise Backup. Here are the steps:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="a">
<li class="listitem">
<p>
Stop the corrupted server, if it is still running. For
example, on Linux distributions that use systemd:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa30376371"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">s3<span class="token operator">></span> systemctl stop mysqld</code></pre>
</div>
</li>
<li class="listitem">
<p>
Preserve the two configuration files in the corrupted
server's data directory,
<code class="filename">
auto.cnf
</code>
and
<code class="filename">
mysqld-auto.cnf
</code>
(if it exists), by
copying them to a safe location outside of the data
directory. This is for preserving the
<a class="link" href="replication-options.html#sysvar_server_uuid">
server's UUID
</a>
and
<a class="xref" href="persisted-system-variables.html" title="7.1.9.3 Persisted System Variables">
Section 7.1.9.3, “Persisted System Variables”
</a>
(if
used), which are needed in the steps below.
</p>
</li>
<li class="listitem">
<p>
Delete all contents in the data directory of
<code class="literal">
s3
</code>
. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa69151254"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">s3> rm <span class="token property">-rf</span> /var/lib/mysql/*</code></pre>
</div>
<p>
If the system variables
<a class="link" href="innodb-parameters.html#sysvar_innodb_data_home_dir">
<code class="literal">
innodb_data_home_dir
</code>
</a>
,
<a class="link" href="innodb-parameters.html#sysvar_innodb_log_group_home_dir">
<code class="literal">
innodb_log_group_home_dir
</code>
</a>
,
and
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
point to any directories other than the data directory,
they should also be made empty; otherwise, the restore
operation fails.
</p>
</li>
<li class="listitem">
<p>
Restore backup of
<code class="literal">
s2
</code>
onto the host for
<code class="literal">
s3
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa65955596"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">s3> mysqlbackup <span class="token constant">--defaults-file</span><span class="token attr-value"><span class="token punctuation">=</span>/etc/my.cnf</span> \
<span class="token constant">--datadir</span><span class="token attr-value"><span class="token punctuation">=</span>/var/lib/mysql</span> \
<span class="token constant">--backup-image</span><span class="token attr-value"><span class="token punctuation">=</span>/backups/my.mbi_2206_1429</span> \
<span class="token constant">--backup-dir</span><span class="token attr-value"><span class="token punctuation">=</span>/tmp/restore_`date</span> +%d%m_%H%M` copy-back-and-apply-log</code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The command above assumes that the binary logs and relay
logs on
<code class="literal">
s2
</code>
and
<code class="literal">
s3
</code>
have the same base name and are at the same location on
the two servers. If these conditions are not met, you
should use the
<a class="ulink" href="/doc/mysql-enterprise-backup/8.4/en/server-repository-options.html#option_meb_log-bin" target="_top">
<code class="option">
--log-bin
</code>
</a>
and
<a class="ulink" href="/doc/mysql-enterprise-backup/8.4/en/server-repository-options.html#option_meb_relay-log" target="_top">
<code class="option">
--relay-log
</code>
</a>
options to
restore the binary log and relay log to their original
file paths on
<code class="literal">
s3
</code>
. For example, if you
know that on
<code class="literal">
s3
</code>
the binary log's base
name is
<code class="literal">
s3-bin
</code>
and the relay-log's
base name is
<code class="literal">
s3-relay-bin
</code>
, your
restore command should look like:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa31323067"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">mysqlbackup <span class="token constant">--defaults-file</span><span class="token attr-value"><span class="token punctuation">=</span>/etc/my.cnf</span> \
<span class="token constant">--datadir</span><span class="token attr-value"><span class="token punctuation">=</span>/var/lib/mysql</span> \
<span class="token constant">--backup-image</span><span class="token attr-value"><span class="token punctuation">=</span>/backups/my.mbi_2206_1429</span> \
<span class="token constant">--log-bin</span><span class="token attr-value"><span class="token punctuation">=</span>s3-bin</span> <span class="token constant">--relay-log</span><span class="token attr-value"><span class="token punctuation">=</span>s3-relay-bin</span> \
<span class="token constant">--backup-dir</span><span class="token attr-value"><span class="token punctuation">=</span>/tmp/restore_`date</span> +%d%m_%H%M` copy-back-and-apply-log</code></pre>
</div>
<p>
Being able to restore the binary log and relay log to
the right file paths makes the restore process easier;
if that is impossible for some reason, see
<a class="xref" href="group-replication-enterprise-backup.html#group-replication-rebuild-member" title="Rebuild the Failed Member to Rejoin as a New Member">
Rebuild the Failed Member to Rejoin as a New Member
</a>
.
</p>
</div>
</li>
</ol>
</div>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Restore the
<code class="filename">
auto.cnf
</code>
file for
s3.
</em>
</span>
To rejoin the replication group, the restored
member
<span class="emphasis">
<em>
must
</em>
</span>
have the same
<a class="link" href="replication-options.html#sysvar_server_uuid">
<code class="literal">
server_uuid
</code>
</a>
it used to join
the group before. Supply the old server UUID by copying the
<code class="filename">
auto.cnf
</code>
file preserved in step 2 above
into the data directory of the restored member.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If you cannot supply the failed member's original
<a class="link" href="replication-options.html#sysvar_server_uuid">
<code class="literal">
server_uuid
</code>
</a>
to the restored
member by restoring its old
<code class="filename">
auto.cnf
</code>
file, you must let the restored member join the group as a
new member; see instructions in
<a class="xref" href="group-replication-enterprise-backup.html#group-replication-rebuild-member" title="Rebuild the Failed Member to Rejoin as a New Member">
Rebuild the Failed Member to Rejoin as a New Member
</a>
below on
how to do that.
</p>
</div>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Restore the
<code class="filename">
mysqld-auto.cnf
</code>
file for s3 (only required if s3 used persistent system
variables).
</em>
</span>
The settings for the
<a class="xref" href="persisted-system-variables.html" title="7.1.9.3 Persisted System Variables">
Section 7.1.9.3, “Persisted System Variables”
</a>
that were used to
configure the failed member must be provided to the restored
member. These settings are to be found in the
<code class="filename">
mysqld-auto.cnf
</code>
file of the failed
server, which you should have preserved in step 2 above.
Restore the file to the data directory of the restored server.
See
<a class="xref" href="group-replication-enterprise-backup.html#group-replication-meb-restore-persisted-variables" title="Restoring Persisted System Variables">
Restoring Persisted System Variables
</a>
on what to do if you do not have a copy of the file.
</p>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Start the restored server.
</em>
</span>
For example,
on Linux distributions that use systemd:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa87433591"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">systemctl start mysqld</code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If the server you are restoring is a primary member, perform
the steps described in
<a class="xref" href="group-replication-enterprise-backup.html#group-replication-meb-restore-primary" title="Restoring a Primary Member">
Restoring a Primary Member
</a>
<span class="emphasis">
<em>
before starting the restored server
</em>
</span>
.
</p>
</div>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Restart Group Replication.
</em>
</span>
Connect to the
restarted
<code class="literal">
s3
</code>
using, for example, a
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client, and issue the following
statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa72156766"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">START</span> <span class="token keyword">GROUP_REPLICATION</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Before the restored instance can become an online member of
the group, it needs to apply any transactions that have
happened to the group after the backup was taken; this is
achieved using Group Replication's
<a class="link" href="group-replication-distributed-recovery.html" title="20.5.4 Distributed Recovery">
distributed
recovery
</a>
mechanism, and the process starts after the
<a class="link" href="start-group-replication.html" title="15.4.3.1 START GROUP_REPLICATION Statement">
START
GROUP_REPLICATION
</a>
statement has been issued. To check
the member status of the restored instance, issue:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa62306035"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> member_host<span class="token punctuation">,</span> member_port<span class="token punctuation">,</span> member_state <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> member_host <span class="token punctuation">|</span> member_port <span class="token punctuation">|</span> member_state <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> s1 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> s2 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> s3 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> RECOVERING <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
This shows that
<code class="literal">
s3
</code>
is applying transactions
to catch up with the group. Once it has caught up with the
rest of the group, its
<code class="literal">
member_state
</code>
changes
to
<code class="literal">
ONLINE
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa12565947"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> member_host<span class="token punctuation">,</span> member_port<span class="token punctuation">,</span> member_state <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> member_host <span class="token punctuation">|</span> member_port <span class="token punctuation">|</span> member_state <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> s1 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> s2 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> s3 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If the server you are restoring is a primary member, once it
has gained synchrony with the group and become
<code class="literal">
ONLINE
</code>
, perform the steps described at
the end of
<a class="xref" href="group-replication-enterprise-backup.html#group-replication-meb-restore-primary" title="Restoring a Primary Member">
Restoring a Primary Member
</a>
to
revert the configuration changes you had made to the server
before you started it.
</p>
</div>
</li>
</ol>
</div>
<p>
The member has now been fully restored from the backup and
functions as a regular member of the group.
</p>
<h4>
<a name="group-replication-rebuild-member">
</a>
Rebuild the Failed Member to Rejoin as a New Member
</h4>
<p>
Sometimes, the steps outlined above in
<a class="xref" href="group-replication-enterprise-backup.html#group-replication-restore-failed-member" title="Restoring a Failed Member">
Restoring a Failed Member
</a>
cannot
be carried out because, for example, the binary log or relay log
is corrupted, or it is just missing from the backup. In such a
situation, use the backup to rebuild the member, and then add it
to the group as a new member. In the steps below, we assume the
rebuilt member is named
<code class="literal">
s3
</code>
, like the failed
member, and that it runs on the same host as
<code class="literal">
s3
</code>
:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
<span class="emphasis">
<em>
Copy the backup of s2 onto the host for s3
.
</em>
</span>
The exact way to copy the backup depends on the
operating system and tools available to you. In this example
we assume the hosts are both Linux servers and use SCP to copy
the files between them:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa34876704"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">s2/backups> scp my<span class="token punctuation">.</span>mbi_2206_1429 s3<span class="token punctuation">:</span>/backups</code></pre>
</div>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Restore the backup.
</em>
</span>
Connect to the target
host (the host for
<code class="literal">
s3
</code>
in this case), and
restore the backup using MySQL Enterprise Backup. Here are the steps:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="a">
<li class="listitem">
<p>
Stop the corrupted server, if it is still running. For
example, on Linux distributions that use systemd:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-simple"><div class="docs-select-all right" id="sa12324338"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-simple">s3<span class="token operator">></span> systemctl stop mysqld</code></pre>
</div>
</li>
<li class="listitem">
<p>
Preserve the configuration file
<code class="filename">
mysqld-auto.cnf
</code>
, if it is found in
the corrupted server's data directory, by copying it to a
safe location outside of the data directory. This is for
preserving the server's
<a class="xref" href="persisted-system-variables.html" title="7.1.9.3 Persisted System Variables">
Section 7.1.9.3, “Persisted System Variables”
</a>
, which are
needed later.
</p>
</li>
<li class="listitem">
<p>
Delete all contents in the data directory of
<code class="literal">
s3
</code>
. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa89115807"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">s3> rm <span class="token property">-rf</span> /var/lib/mysql/*</code></pre>
</div>
<p>
If the system variables
<a class="link" href="innodb-parameters.html#sysvar_innodb_data_home_dir">
<code class="literal">
innodb_data_home_dir
</code>
</a>
,
<a class="link" href="innodb-parameters.html#sysvar_innodb_log_group_home_dir">
<code class="literal">
innodb_log_group_home_dir
</code>
</a>
,
and
<a class="link" href="innodb-parameters.html#sysvar_innodb_undo_directory">
<code class="literal">
innodb_undo_directory
</code>
</a>
point to any directories other than the data directory,
they should also be made empty; otherwise, the restore
operation fails.
</p>
</li>
<li class="listitem">
<p>
Restore the backup of
<code class="literal">
s2
</code>
onto the host
of
<code class="literal">
s3
</code>
. With this approach, we are
rebuilding
<code class="literal">
<code class="literal">
s3
</code>
</code>
as a
new member, for which we do not need or do not want to use
the old binary and relay logs in the backup; therefore, if
these logs have been included in your backup, exclude them
using the
<a class="ulink" href="/doc/mysql-enterprise-backup/8.4/en/backup-capacity-options.html#option_meb_skip-binlog" target="_top">
<code class="option">
--skip-binlog
</code>
</a>
and
<a class="ulink" href="/doc/mysql-enterprise-backup/8.4/en/backup-capacity-options.html#option_meb_skip-relaylog" target="_top">
<code class="option">
--skip-relaylog
</code>
</a>
options:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa73627464"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">s3> mysqlbackup <span class="token constant">--defaults-file</span><span class="token attr-value"><span class="token punctuation">=</span>/etc/my.cnf</span> \
<span class="token constant">--datadir</span><span class="token attr-value"><span class="token punctuation">=</span>/var/lib/mysql</span> \
<span class="token constant">--backup-image</span><span class="token attr-value"><span class="token punctuation">=</span>/backups/my.mbi_2206_1429</span> \
<span class="token constant">--backup-dir</span><span class="token attr-value"><span class="token punctuation">=</span>/tmp/restore_`date</span> +%d%m_%H%M` \
<span class="token property">--skip-binlog</span> <span class="token property">--skip-relaylog</span> \
copy-back-and-apply-log</code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If you have healthy binary log and relay logs in the
backup that you can transfer onto the target host with
no issues, you are recommended to follow the easier
procedure as described in
<a class="xref" href="group-replication-enterprise-backup.html#group-replication-restore-failed-member" title="Restoring a Failed Member">
Restoring a Failed Member
</a>
above.
</p>
</div>
</li>
</ol>
</div>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Restore the
<code class="filename">
mysqld-auto.cnf
</code>
file for s3 (only required if s3 used persistent system
variables).
</em>
</span>
The settings for the
<a class="xref" href="persisted-system-variables.html" title="7.1.9.3 Persisted System Variables">
Section 7.1.9.3, “Persisted System Variables”
</a>
that were used to
configure the failed member must be provided to the restored
server. These settings are to be found in the
<code class="filename">
mysqld-auto.cnf
</code>
file of the failed
server, which you should have preserved in step 2 above.
Restore the file to the data directory of the restored server.
See
<a class="xref" href="group-replication-enterprise-backup.html#group-replication-meb-restore-persisted-variables" title="Restoring Persisted System Variables">
Restoring Persisted System Variables
</a>
on what to do if you do not have a copy of the file.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Do NOT restore the corrupted server's
<code class="filename">
auto.cnf
</code>
file to the data directory of
the new member—when the rebuilt
<code class="literal">
s3
</code>
joins the group as a new member, it is going to be assigned
a new server UUID.
</p>
</div>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Start the restored server.
</em>
</span>
For example,
on Linux distributions that use systemd:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa95482513"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">systemctl start mysqld</code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If the server you are restoring is a primary member, perform
the steps described in
<a class="xref" href="group-replication-enterprise-backup.html#group-replication-meb-restore-primary" title="Restoring a Primary Member">
Restoring a Primary Member
</a>
<span class="emphasis">
<em>
before starting the restored server
</em>
</span>
.
</p>
</div>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Reconfigure the restored member to join Group
Replication.
</em>
</span>
Connect to the restored server with a
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client and reset the source and
replica information with the following statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34867085"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">RESET</span> <span class="token datatype">BINARY</span> <span class="token keyword">LOGS</span> <span class="token operator">AND</span> GTIDS<span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">RESET</span> <span class="token keyword">REPLICA</span> <span class="token keyword">ALL</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For the restored server to be able to recover automatically
using Group Replication's built-in mechanism for
<a class="link" href="group-replication-distributed-recovery.html" title="20.5.4 Distributed Recovery">
distributed
recovery
</a>
, configure the server's
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
variable. To do
this, use the
<code class="filename">
backup_gtid_executed.sql
</code>
file included in the backup of
<code class="literal">
s2
</code>
, which is
usually restored under the restored member's data directory.
Disable binary logging, use the
<code class="filename">
backup_gtid_executed.sql
</code>
file to
configure
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
, and
then re-enable binary logging by issuing the following
statements with your
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa36626696"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> SQL_LOG_BIN<span class="token operator">=</span><span class="token keyword">OFF</span><span class="token punctuation">;</span>
<span class="token prompt">mysql></span> <span class="token keyword">SOURCE</span> <em class="replaceable">datadir</em><span class="token operator">/</span>backup_gtid_executed<span class="token punctuation">.</span><span class="token keyword">sql</span>
<span class="token prompt">mysql></span> <span class="token keyword">SET</span> SQL_LOG_BIN<span class="token operator">=</span><span class="token keyword">ON</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Then, configure the
<a class="link" href="group-replication-user-credentials.html" title="20.2.1.3 User Credentials For Distributed Recovery">
Group
Replication user credentials
</a>
on the member using the
SQL statements shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa546456"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CHANGE</span> <span class="token keyword">REPLICATION</span> <span class="token keyword">SOURCE</span> <span class="token keyword">TO</span> <span class="token keyword">SOURCE_USER</span><span class="token operator">=</span><span class="token string">'<em class="replaceable">rpl_user</em>'</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">SOURCE_PASSWORD</span><span class="token operator">=</span><span class="token string">'<em class="replaceable">password</em>'</span>
<span class="token prompt"> -></span> <span class="token keyword">FOR</span> <span class="token keyword">CHANNEL</span> <span class="token string">'group_replication_recovery'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Restart Group Replication.
</em>
</span>
Issue the
following statement to the restored server with your
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa31682683"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">START</span> <span class="token keyword">GROUP_REPLICATION</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Before the restored instance can become an online member of
the group, it needs to apply any transactions that have
happened to the group after the backup was taken; this is
achieved using Group Replication's
<a class="link" href="group-replication-distributed-recovery.html" title="20.5.4 Distributed Recovery">
distributed
recovery
</a>
mechanism, and the process starts after the
<a class="link" href="start-group-replication.html" title="15.4.3.1 START GROUP_REPLICATION Statement">
START
GROUP_REPLICATION
</a>
statement has been issued. To check
the member status of the restored instance, issue:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa8444444"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> member_host<span class="token punctuation">,</span> member_port<span class="token punctuation">,</span> member_state <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> member_host <span class="token punctuation">|</span> member_port <span class="token punctuation">|</span> member_state <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> s3 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> RECOVERING <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> s2 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> s1 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
This shows that
<code class="literal">
s3
</code>
is applying transactions
to catch up with the group. Once it has caught up with the
rest of the group, its
<code class="literal">
member_state
</code>
changes
to
<code class="literal">
ONLINE
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa10403582"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> member_host<span class="token punctuation">,</span> member_port<span class="token punctuation">,</span> member_state <span class="token keyword">FROM</span> performance_schema<span class="token punctuation">.</span>replication_group_members<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> member_host <span class="token punctuation">|</span> member_port <span class="token punctuation">|</span> member_state <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> s3 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> s2 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> s1 <span class="token punctuation">|</span> 3306 <span class="token punctuation">|</span> ONLINE <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If the server you are restoring is a primary member, once it
has gained synchrony with the group and become
<code class="literal">
ONLINE
</code>
, perform the steps described at
the end of
<a class="xref" href="group-replication-enterprise-backup.html#group-replication-meb-restore-primary" title="Restoring a Primary Member">
Restoring a Primary Member
</a>
to
revert the configuration changes you had made to the server
before you started it.
</p>
</div>
</li>
</ol>
</div>
<p>
The member has now been restored to the group as a new member.
</p>
<p>
<a name="group-replication-meb-restore-persisted-variables">
</a>
<b>
Restoring Persisted System Variables.
</b>
<span class="command">
<strong>
mysqlbackup
</strong>
</span>
does not provide support for
backing up or preserving
<a class="xref" href="persisted-system-variables.html" title="7.1.9.3 Persisted System Variables">
Section 7.1.9.3, “Persisted System Variables”
</a>
—the file
<code class="filename">
mysqld-auto.cnf
</code>
is not included in a
backup. To start the restored member with its persisted variable
settings, you need to do one of the following:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Preserve a copy of the
<code class="filename">
mysqld-auto.cnf
</code>
file from the corrupted server, and copy it to the restored
server's data directory.
</p>
</li>
<li class="listitem">
<p>
Copy the
<code class="filename">
mysqld-auto.cnf
</code>
file from
another member of the group into the restored server's data
directory, if that member has the same persisted system
variable settings as the corrupted member.
</p>
</li>
<li class="listitem">
<p>
After the restored server is started and before you restart
Group Replication, set all the system variables manually to
their persisted values through a
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client.
</p>
</li>
</ul>
</div>
<p>
<a name="group-replication-meb-restore-primary">
</a>
<b>
Restoring a Primary Member.
</b>
If the restored member is a primary in the group, care must be
taken to prevent writes to the restored database during the
Group Replication distributed recovery process. Depending on how
the group is accessed by clients, there is a possibility of DML
statements being executed on the restored member once it becomes
accessible on the network, prior to the member finishing its
catch-up on the activities it has missed while off the group. To
avoid this,
<span class="emphasis">
<em>
before starting the restored
server
</em>
</span>
, configure the following system variables in
the server option file:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa40131917"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token constant">group_replication_start_on_boot</span><span class="token attr-value"><span class="token punctuation">=</span>OFF</span>
<span class="token constant">super_read_only</span><span class="token attr-value"><span class="token punctuation">=</span>ON</span>
<span class="token constant">event_scheduler</span><span class="token attr-value"><span class="token punctuation">=</span>OFF</span></code></pre>
</div>
<p>
These settings ensure that the member becomes read-only at
startup, and that the event scheduler is turned off while the
member catches up with the group during the distributed recovery
process. Adequate error handling must also be provided for on the
clients, since they are unable to perform DML operations during
this period on the member being restored.
</p>
<p>
Once the restoration process is fully completed and the restored
member is synchronized with the rest of the group, you can revert
these changes. First, restart the event scheduler using the
statement shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa65183805"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">global</span> event_scheduler<span class="token operator">=</span><span class="token keyword">ON</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
After this, you should set the following system variables in the
member's option file, so that they have the necessary values
for the next time that the member is started:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-ini"><div class="docs-select-all right" id="sa43412420"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-ini"><span class="token constant">group_replication_start_on_boot</span><span class="token attr-value"><span class="token punctuation">=</span>ON</span>
<span class="token constant">super_read_only</span><span class="token attr-value"><span class="token punctuation">=</span>OFF</span>
<span class="token constant">event_scheduler</span><span class="token attr-value"><span class="token punctuation">=</span>ON</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-ps-setup-show-disabled-consumers.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-ps-setup-show-disabled-consumers">
</a>
30.4.4.16 The ps_setup_show_disabled_consumers() Procedure
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045061360688">
</a>
<a class="indexterm" name="idm46045061359168">
</a>
<p>
Displays all currently disabled Performance Schema consumers.
</p>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-ps-setup-show-disabled-consumers-parameters">
</a>
Parameters
</h5>
</div>
</div>
</div>
<p>
None.
</p>
</div>
<div class="simplesect">
<div class="titlepage">
<div>
<div class="simple">
<h5 class="title">
<a name="sys-ps-setup-show-disabled-consumers-example">
</a>
Example
</h5>
</div>
</div>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51239372"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">CALL</span> sys<span class="token punctuation">.</span>ps_setup_show_disabled_consumers<span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> disabled_consumers <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> events_stages_current <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_stages_history <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_stages_history_long <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_statements_history <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_statements_history_long <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_transactions_history <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_transactions_history_long <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_waits_current <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_waits_history <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> events_waits_history_long <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/derived-tables.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="derived-tables">
</a>
15.2.15.8 Derived Tables
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045179768640">
</a>
<a class="indexterm" name="idm46045179767568">
</a>
<a class="indexterm" name="idm46045179765664">
</a>
<p>
This section discusses general characteristics of derived
tables. For information about lateral derived tables preceded by
the
<code class="literal">
LATERAL
</code>
keyword, see
<a class="xref" href="lateral-derived-tables.html" title="15.2.15.9 Lateral Derived Tables">
Section 15.2.15.9, “Lateral Derived Tables”
</a>
.
</p>
<p>
A derived table is an expression that generates a table within
the scope of a query
<code class="literal">
FROM
</code>
clause. For
example, a subquery in a
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statement
<code class="literal">
FROM
</code>
clause is a derived table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa98808507"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">FROM</span> <span class="token punctuation">(</span><em class="replaceable">subquery</em><span class="token punctuation">)</span> <span class="token punctuation">[</span><span class="token keyword">AS</span><span class="token punctuation">]</span> <em class="replaceable">tbl_name</em> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre>
</div>
<p>
The
<a class="link" href="json-table-functions.html#function_json-table">
<code class="literal">
JSON_TABLE()
</code>
</a>
function
generates a table and provides another way to create a derived
table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa99731472"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> <span class="token keyword">JSON_TABLE</span><span class="token punctuation">(</span><em class="replaceable">arg_list</em><span class="token punctuation">)</span> <span class="token punctuation">[</span><span class="token keyword">AS</span><span class="token punctuation">]</span> <em class="replaceable">tbl_name</em> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre>
</div>
<p>
The
<code class="literal">
[AS]
<em class="replaceable">
<code>
tbl_name
</code>
</em>
</code>
clause is mandatory because every table in a
<code class="literal">
FROM
</code>
clause must have a name. Any columns in
the derived table must have unique names. Alternatively,
<em class="replaceable">
<code>
tbl_name
</code>
</em>
may be followed by a
parenthesized list of names for the derived table columns:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa15777972"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span> <span class="token keyword">FROM</span> <span class="token punctuation">(</span><em class="replaceable">subquery</em><span class="token punctuation">)</span> <span class="token punctuation">[</span><span class="token keyword">AS</span><span class="token punctuation">]</span> <em class="replaceable">tbl_name</em> <span class="token punctuation">(</span><em class="replaceable">col_list</em><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre>
</div>
<p>
The number of column names must be the same as the number of
table columns.
</p>
<p>
For the sake of illustration, assume that you have this table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa14370418"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span>s1 <span class="token datatype">INT</span><span class="token punctuation">,</span> s2 <span class="token datatype">CHAR</span><span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">,</span> s3 <span class="token datatype">FLOAT</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Here is how to use a subquery in the
<code class="literal">
FROM
</code>
clause, using the example table:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16086259"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token string">'1'</span><span class="token punctuation">,</span><span class="token number">1.0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t1 <span class="token keyword">VALUES</span> <span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token string">'2'</span><span class="token punctuation">,</span><span class="token number">2.0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> sb1<span class="token punctuation">,</span>sb2<span class="token punctuation">,</span>sb3
<span class="token keyword">FROM</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> s1 <span class="token keyword">AS</span> sb1<span class="token punctuation">,</span> s2 <span class="token keyword">AS</span> sb2<span class="token punctuation">,</span> s3<span class="token operator">*</span><span class="token number">2</span> <span class="token keyword">AS</span> sb3 <span class="token keyword">FROM</span> t1<span class="token punctuation">)</span> <span class="token keyword">AS</span> sb
<span class="token keyword">WHERE</span> sb1 <span class="token operator">></span> <span class="token number">1</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Result:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa26829867"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">+------+------+------+
| sb1 | sb2 | sb3 |
+------+------+------+
| 2 | 2 | 4 |
+------+------+------+</code></pre>
</div>
<p>
Here is another example: Suppose that you want to know the
average of a set of sums for a grouped table. This does not
work:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa82399139"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">AVG</span><span class="token punctuation">(</span><span class="token function">SUM</span><span class="token punctuation">(</span>column1<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">FROM</span> t1 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> column1<span class="token punctuation">;</span></code></pre>
</div>
<p>
However, this query provides the desired information:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa86667387"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SELECT</span> <span class="token function">AVG</span><span class="token punctuation">(</span>sum_column1<span class="token punctuation">)</span>
<span class="token keyword">FROM</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token function">SUM</span><span class="token punctuation">(</span>column1<span class="token punctuation">)</span> <span class="token keyword">AS</span> sum_column1
<span class="token keyword">FROM</span> t1 <span class="token keyword">GROUP</span> <span class="token keyword">BY</span> column1<span class="token punctuation">)</span> <span class="token keyword">AS</span> t1<span class="token punctuation">;</span></code></pre>
</div>
<p>
Notice that the column name used within the subquery
(
<code class="literal">
sum_column1
</code>
) is recognized in the outer
query.
</p>
<p>
The column names for a derived table come from its select list:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa93620597"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> dt<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 4 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 4 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
To provide column names explicitly, follow the derived table
name with a parenthesized list of column names:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa10167363"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> <span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> dt <span class="token punctuation">(</span>a<span class="token punctuation">,</span> b<span class="token punctuation">,</span> c<span class="token punctuation">,</span> d<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> a <span class="token punctuation">|</span> b <span class="token punctuation">|</span> c <span class="token punctuation">|</span> d <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 1 <span class="token punctuation">|</span> 2 <span class="token punctuation">|</span> 3 <span class="token punctuation">|</span> 4 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<p>
A derived table can return a scalar, column, row, or table.
</p>
<p>
Derived tables are subject to these restrictions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
A derived table cannot contain references to other tables of
the same
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
(use a
<code class="literal">
LATERAL
</code>
derived table for that; see
<a class="xref" href="lateral-derived-tables.html" title="15.2.15.9 Lateral Derived Tables">
Section 15.2.15.9, “Lateral Derived Tables”
</a>
).
</p>
</li>
</ul>
</div>
<p>
The optimizer determines information about derived tables in
such a way that
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
does not
need to materialize them. See
<a class="xref" href="derived-table-optimization.html" title="10.2.2.4 Optimizing Derived Tables, View References, and Common Table Expressions with Merging or Materialization">
Section 10.2.2.4, “Optimizing Derived Tables, View References, and Common Table Expressions
with Merging or Materialization”
</a>
.
</p>
<p>
It is possible under certain circumstances that using
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
SELECT
</code>
</a>
modifies table data. This can occur if the
outer query accesses any tables and an inner query invokes a
stored function that changes one or more rows of a table.
Suppose that there are two tables
<code class="literal">
t1
</code>
and
<code class="literal">
t2
</code>
in database
<code class="literal">
d1
</code>
, and a
stored function
<code class="literal">
f1
</code>
that modifies
<code class="literal">
t2
</code>
, created as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa22767578"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">CREATE</span> <span class="token keyword">DATABASE</span> d1<span class="token punctuation">;</span>
<span class="token keyword">USE</span> d1<span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t1 <span class="token punctuation">(</span>c1 <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> t2 <span class="token punctuation">(</span>c1 <span class="token datatype">INT</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token keyword">FUNCTION</span> f1<span class="token punctuation">(</span>p1 <span class="token datatype">INT</span><span class="token punctuation">)</span> <span class="token keyword">RETURNS</span> <span class="token datatype">INT</span>
<span class="token keyword">BEGIN</span>
<span class="token keyword">INSERT</span> <span class="token keyword">INTO</span> t2 <span class="token keyword">VALUES</span> <span class="token punctuation">(</span>p1<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">RETURN</span> p1<span class="token punctuation">;</span>
<span class="token keyword">END</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Referencing the function directly in an
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
SELECT
</code>
</a>
has no effect on
<code class="literal">
t2
</code>
, as
shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa16846145"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t2<span class="token punctuation">;</span>
<span class="token output">Empty set (0.02 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">EXPLAIN</span> <span class="token keyword">SELECT</span> f1<span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span>\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
id<span class="token punctuation">:</span> 1
select_type<span class="token punctuation">:</span> SIMPLE
table<span class="token punctuation">:</span> NULL
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> NULL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> NULL
filtered<span class="token punctuation">:</span> NULL
Extra<span class="token punctuation">:</span> No tables used
</span><span class="token output">1 row in set (0.01 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t2<span class="token punctuation">;</span>
<span class="token output">Empty set (0.01 sec)</span></code></pre>
</div>
<p>
This is because the
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
statement did not reference any tables, as can be seen in the
<code class="literal">
table
</code>
and
<code class="literal">
Extra
</code>
columns of
the output. This is also true of the following nested
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa29875391"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">EXPLAIN</span> <span class="token keyword">SELECT</span> <span class="token function">NOW</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> a1<span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> f1<span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> a2\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
id<span class="token punctuation">:</span> 1
select_type<span class="token punctuation">:</span> PRIMARY
table<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> NULL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> NULL
filtered<span class="token punctuation">:</span> NULL
Extra<span class="token punctuation">:</span> No tables used
</span><span class="token output">1 row in set, 1 warning (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">WARNINGS</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Level <span class="token punctuation">|</span> Code <span class="token punctuation">|</span> Message <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Note <span class="token punctuation">|</span> 1249 <span class="token punctuation">|</span> Select 2 was reduced during optimization <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t2<span class="token punctuation">;</span>
<span class="token output">Empty set (0.00 sec)</span></code></pre>
</div>
<p>
However, if the outer
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
references any tables, the optimizer executes the statement in
the subquery as well, with the result that
<code class="literal">
t2
</code>
is modified:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa69583569"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">EXPLAIN</span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t1 <span class="token keyword">AS</span> a1<span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token keyword">SELECT</span> f1<span class="token punctuation">(</span><span class="token number">5</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token keyword">AS</span> a2\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
id<span class="token punctuation">:</span> 1
select_type<span class="token punctuation">:</span> PRIMARY
table<span class="token punctuation">:</span> <derived2>
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> system
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 1
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> NULL
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 2. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
id<span class="token punctuation">:</span> 1
select_type<span class="token punctuation">:</span> PRIMARY
table<span class="token punctuation">:</span> a1
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ALL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> 1
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> NULL
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 3. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
id<span class="token punctuation">:</span> 2
select_type<span class="token punctuation">:</span> DERIVED
table<span class="token punctuation">:</span> NULL
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> NULL
possible_keys<span class="token punctuation">:</span> NULL
key<span class="token punctuation">:</span> NULL
key_len<span class="token punctuation">:</span> NULL
ref<span class="token punctuation">:</span> NULL
rows<span class="token punctuation">:</span> NULL
filtered<span class="token punctuation">:</span> NULL
Extra<span class="token punctuation">:</span> No tables used
</span><span class="token output">3 rows in set (0.00 sec)</span>
<span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> t2<span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> c1 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> 5 <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output">1 row in set (0.00 sec)</span></code></pre>
</div>
<p>
The derived table optimization can also be employed with many
correlated (scalar) subqueries. For more information and
examples, see
<a class="xref" href="correlated-subqueries.html" title="15.2.15.7 Correlated Subqueries">
Section 15.2.15.7, “Correlated Subqueries”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/alter-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="alter-table">
</a>
15.1.9 ALTER TABLE Statement
</h3>
</div>
</div>
</div>
<div class="toc">
<dl class="toc">
<dt>
<span class="section">
<a href="alter-table-partition-operations.html">
15.1.9.1 ALTER TABLE Partition Operations
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-table-generated-columns.html">
15.1.9.2 ALTER TABLE and Generated Columns
</a>
</span>
</dt>
<dt>
<span class="section">
<a href="alter-table-examples.html">
15.1.9.3 ALTER TABLE Examples
</a>
</span>
</dt>
</dl>
</div>
<a class="indexterm" name="idm46045189579920">
</a>
<a class="indexterm" name="idm46045189578848">
</a>
<a class="indexterm" name="idm46045189577360">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa70194336"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em>
<span class="token punctuation">[</span><em class="replaceable">alter_option</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">alter_option</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">]</span>
<span class="token punctuation">[</span><em class="replaceable">partition_options</em><span class="token punctuation">]</span>
<em class="replaceable">alter_option</em>: {
<em class="replaceable">table_options</em>
<span class="token operator">|</span> <span class="token keyword">ADD</span> <span class="token punctuation">[</span><span class="token keyword">COLUMN</span><span class="token punctuation">]</span> <em class="replaceable">col_name</em> <em class="replaceable">column_definition</em>
<span class="token punctuation">[</span><span class="token keyword">FIRST</span> <span class="token operator">|</span> <span class="token keyword">AFTER</span> <em class="replaceable">col_name</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">ADD</span> <span class="token punctuation">[</span><span class="token keyword">COLUMN</span><span class="token punctuation">]</span> <span class="token punctuation">(</span><em class="replaceable">col_name</em> <em class="replaceable">column_definition</em><span class="token punctuation">,</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span>
<span class="token operator">|</span> <span class="token keyword">ADD</span> {<span class="token keyword">INDEX</span> <span class="token operator">|</span> <span class="token keyword">KEY</span>} <span class="token punctuation">[</span><em class="replaceable">index_name</em><span class="token punctuation">]</span>
<span class="token punctuation">[</span><em class="replaceable">index_type</em><span class="token punctuation">]</span> <span class="token punctuation">(</span><em class="replaceable">key_part</em><span class="token punctuation">,</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span> <span class="token punctuation">[</span><em class="replaceable">index_option</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token operator">|</span> <span class="token keyword">ADD</span> {<span class="token keyword">FULLTEXT</span> <span class="token operator">|</span> <span class="token keyword">SPATIAL</span>} <span class="token punctuation">[</span><span class="token keyword">INDEX</span> <span class="token operator">|</span> <span class="token keyword">KEY</span><span class="token punctuation">]</span> <span class="token punctuation">[</span><em class="replaceable">index_name</em><span class="token punctuation">]</span>
<span class="token punctuation">(</span><em class="replaceable">key_part</em><span class="token punctuation">,</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span> <span class="token punctuation">[</span><em class="replaceable">index_option</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token operator">|</span> <span class="token keyword">ADD</span> <span class="token punctuation">[</span><span class="token keyword">CONSTRAINT</span> <span class="token punctuation">[</span><em class="replaceable">symbol</em><span class="token punctuation">]</span><span class="token punctuation">]</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span>
<span class="token punctuation">[</span><em class="replaceable">index_type</em><span class="token punctuation">]</span> <span class="token punctuation">(</span><em class="replaceable">key_part</em><span class="token punctuation">,</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span>
<span class="token punctuation">[</span><em class="replaceable">index_option</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token operator">|</span> <span class="token keyword">ADD</span> <span class="token punctuation">[</span><span class="token keyword">CONSTRAINT</span> <span class="token punctuation">[</span><em class="replaceable">symbol</em><span class="token punctuation">]</span><span class="token punctuation">]</span> <span class="token keyword">UNIQUE</span> <span class="token punctuation">[</span><span class="token keyword">INDEX</span> <span class="token operator">|</span> <span class="token keyword">KEY</span><span class="token punctuation">]</span>
<span class="token punctuation">[</span><em class="replaceable">index_name</em><span class="token punctuation">]</span> <span class="token punctuation">[</span><em class="replaceable">index_type</em><span class="token punctuation">]</span> <span class="token punctuation">(</span><em class="replaceable">key_part</em><span class="token punctuation">,</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span>
<span class="token punctuation">[</span><em class="replaceable">index_option</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token operator">|</span> <span class="token keyword">ADD</span> <span class="token punctuation">[</span><span class="token keyword">CONSTRAINT</span> <span class="token punctuation">[</span><em class="replaceable">symbol</em><span class="token punctuation">]</span><span class="token punctuation">]</span> <span class="token keyword">FOREIGN</span> <span class="token keyword">KEY</span>
<span class="token punctuation">[</span><em class="replaceable">index_name</em><span class="token punctuation">]</span> <span class="token punctuation">(</span><em class="replaceable">col_name</em><span class="token punctuation">,</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span>
<em class="replaceable">reference_definition</em>
<span class="token operator">|</span> <span class="token keyword">ADD</span> <span class="token punctuation">[</span><span class="token keyword">CONSTRAINT</span> <span class="token punctuation">[</span><em class="replaceable">symbol</em><span class="token punctuation">]</span><span class="token punctuation">]</span> <span class="token keyword">CHECK</span> <span class="token punctuation">(</span><em class="replaceable">expr</em><span class="token punctuation">)</span> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> <span class="token keyword">ENFORCED</span><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">DROP</span> {<span class="token keyword">CHECK</span> <span class="token operator">|</span> <span class="token keyword">CONSTRAINT</span>} <em class="replaceable">symbol</em>
<span class="token operator">|</span> <span class="token keyword">ALTER</span> {<span class="token keyword">CHECK</span> <span class="token operator">|</span> <span class="token keyword">CONSTRAINT</span>} <em class="replaceable">symbol</em> <span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> <span class="token keyword">ENFORCED</span>
<span class="token operator">|</span> <span class="token keyword">ALGORITHM</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token keyword">DEFAULT</span> <span class="token operator">|</span> INSTANT <span class="token operator">|</span> <span class="token keyword">INPLACE</span> <span class="token operator">|</span> <span class="token keyword">COPY</span>}
<span class="token operator">|</span> <span class="token keyword">ALTER</span> <span class="token punctuation">[</span><span class="token keyword">COLUMN</span><span class="token punctuation">]</span> <em class="replaceable">col_name</em> {
<span class="token keyword">SET</span> <span class="token keyword">DEFAULT</span> {<em class="replaceable">literal</em> <span class="token operator">|</span> <span class="token punctuation">(</span><em class="replaceable">expr</em><span class="token punctuation">)</span>}
<span class="token operator">|</span> <span class="token keyword">SET</span> {<span class="token keyword">VISIBLE</span> <span class="token operator">|</span> <span class="token keyword">INVISIBLE</span>}
<span class="token operator">|</span> <span class="token keyword">DROP</span> <span class="token keyword">DEFAULT</span>
}
<span class="token operator">|</span> <span class="token keyword">ALTER</span> <span class="token keyword">INDEX</span> <em class="replaceable">index_name</em> {<span class="token keyword">VISIBLE</span> <span class="token operator">|</span> <span class="token keyword">INVISIBLE</span>}
<span class="token operator">|</span> <span class="token keyword">CHANGE</span> <span class="token punctuation">[</span><span class="token keyword">COLUMN</span><span class="token punctuation">]</span> <em class="replaceable">old_col_name</em> <em class="replaceable">new_col_name</em> <em class="replaceable">column_definition</em>
<span class="token punctuation">[</span><span class="token keyword">FIRST</span> <span class="token operator">|</span> <span class="token keyword">AFTER</span> <em class="replaceable">col_name</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token punctuation">[</span><span class="token keyword">DEFAULT</span><span class="token punctuation">]</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <em class="replaceable">charset_name</em> <span class="token punctuation">[</span><span class="token keyword">COLLATE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <em class="replaceable">collation_name</em><span class="token punctuation">]</span>
<span class="token operator">|</span> CONVERT <span class="token keyword">TO</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <em class="replaceable">charset_name</em> <span class="token punctuation">[</span><span class="token keyword">COLLATE</span> <em class="replaceable">collation_name</em><span class="token punctuation">]</span>
<span class="token operator">|</span> {<span class="token keyword">DISABLE</span> <span class="token operator">|</span> <span class="token keyword">ENABLE</span>} <span class="token keyword">KEYS</span>
<span class="token operator">|</span> {<span class="token keyword">DISCARD</span> <span class="token operator">|</span> <span class="token keyword">IMPORT</span>} <span class="token keyword">TABLESPACE</span>
<span class="token operator">|</span> <span class="token keyword">DROP</span> <span class="token punctuation">[</span><span class="token keyword">COLUMN</span><span class="token punctuation">]</span> <em class="replaceable">col_name</em>
<span class="token operator">|</span> <span class="token keyword">DROP</span> {<span class="token keyword">INDEX</span> <span class="token operator">|</span> <span class="token keyword">KEY</span>} <em class="replaceable">index_name</em>
<span class="token operator">|</span> <span class="token keyword">DROP</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span>
<span class="token operator">|</span> <span class="token keyword">DROP</span> <span class="token keyword">FOREIGN</span> <span class="token keyword">KEY</span> <em class="replaceable">fk_symbol</em>
<span class="token operator">|</span> <span class="token keyword">FORCE</span>
<span class="token operator">|</span> <span class="token keyword">LOCK</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token keyword">DEFAULT</span> <span class="token operator">|</span> <span class="token keyword">NONE</span> <span class="token operator">|</span> <span class="token keyword">SHARED</span> <span class="token operator">|</span> <span class="token keyword">EXCLUSIVE</span>}
<span class="token operator">|</span> <span class="token keyword">MODIFY</span> <span class="token punctuation">[</span><span class="token keyword">COLUMN</span><span class="token punctuation">]</span> <em class="replaceable">col_name</em> <em class="replaceable">column_definition</em>
<span class="token punctuation">[</span><span class="token keyword">FIRST</span> <span class="token operator">|</span> <span class="token keyword">AFTER</span> <em class="replaceable">col_name</em><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">ORDER</span> <span class="token keyword">BY</span> <em class="replaceable">col_name</em> <span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">col_name</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token operator">|</span> <span class="token keyword">RENAME</span> <span class="token keyword">COLUMN</span> <em class="replaceable">old_col_name</em> <span class="token keyword">TO</span> <em class="replaceable">new_col_name</em>
<span class="token operator">|</span> <span class="token keyword">RENAME</span> {<span class="token keyword">INDEX</span> <span class="token operator">|</span> <span class="token keyword">KEY</span>} <em class="replaceable">old_index_name</em> <span class="token keyword">TO</span> <em class="replaceable">new_index_name</em>
<span class="token operator">|</span> <span class="token keyword">RENAME</span> <span class="token punctuation">[</span><span class="token keyword">TO</span> <span class="token operator">|</span> <span class="token keyword">AS</span><span class="token punctuation">]</span> <em class="replaceable">new_tbl_name</em>
<span class="token operator">|</span> {<span class="token keyword">WITHOUT</span> <span class="token operator">|</span> <span class="token keyword">WITH</span>} <span class="token keyword">VALIDATION</span>
}
<em class="replaceable">partition_options</em>:
<em class="replaceable">partition_option</em> <span class="token punctuation">[</span><em class="replaceable">partition_option</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<em class="replaceable">partition_option</em>: {
<span class="token keyword">ADD</span> <span class="token keyword">PARTITION</span> <span class="token punctuation">(</span><em class="replaceable">partition_definition</em><span class="token punctuation">)</span>
<span class="token operator">|</span> <span class="token keyword">DROP</span> <span class="token keyword">PARTITION</span> <em class="replaceable">partition_names</em>
<span class="token operator">|</span> <span class="token keyword">DISCARD</span> <span class="token keyword">PARTITION</span> {<em class="replaceable">partition_names</em> <span class="token operator">|</span> <span class="token keyword">ALL</span>} <span class="token keyword">TABLESPACE</span>
<span class="token operator">|</span> <span class="token keyword">IMPORT</span> <span class="token keyword">PARTITION</span> {<em class="replaceable">partition_names</em> <span class="token operator">|</span> <span class="token keyword">ALL</span>} <span class="token keyword">TABLESPACE</span>
<span class="token operator">|</span> <span class="token keyword">TRUNCATE</span> <span class="token keyword">PARTITION</span> {<em class="replaceable">partition_names</em> <span class="token operator">|</span> <span class="token keyword">ALL</span>}
<span class="token operator">|</span> <span class="token keyword">COALESCE</span> <span class="token keyword">PARTITION</span> <span class="token keyword"><em class="replaceable">number</em></span>
<span class="token operator">|</span> <span class="token keyword">REORGANIZE</span> <span class="token keyword">PARTITION</span> <em class="replaceable">partition_names</em> <span class="token keyword">INTO</span> <span class="token punctuation">(</span><em class="replaceable">partition_definitions</em><span class="token punctuation">)</span>
<span class="token operator">|</span> <span class="token keyword">EXCHANGE</span> <span class="token keyword">PARTITION</span> <em class="replaceable">partition_name</em> <span class="token keyword">WITH</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em> <span class="token punctuation">[</span>{<span class="token keyword">WITH</span> <span class="token operator">|</span> <span class="token keyword">WITHOUT</span>} <span class="token keyword">VALIDATION</span><span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">ANALYZE</span> <span class="token keyword">PARTITION</span> {<em class="replaceable">partition_names</em> <span class="token operator">|</span> <span class="token keyword">ALL</span>}
<span class="token operator">|</span> <span class="token keyword">CHECK</span> <span class="token keyword">PARTITION</span> {<em class="replaceable">partition_names</em> <span class="token operator">|</span> <span class="token keyword">ALL</span>}
<span class="token operator">|</span> <span class="token keyword">OPTIMIZE</span> <span class="token keyword">PARTITION</span> {<em class="replaceable">partition_names</em> <span class="token operator">|</span> <span class="token keyword">ALL</span>}
<span class="token operator">|</span> <span class="token keyword">REBUILD</span> <span class="token keyword">PARTITION</span> {<em class="replaceable">partition_names</em> <span class="token operator">|</span> <span class="token keyword">ALL</span>}
<span class="token operator">|</span> <span class="token keyword">REPAIR</span> <span class="token keyword">PARTITION</span> {<em class="replaceable">partition_names</em> <span class="token operator">|</span> <span class="token keyword">ALL</span>}
<span class="token operator">|</span> <span class="token keyword">REMOVE</span> <span class="token keyword">PARTITIONING</span>
}
<em class="replaceable">key_part</em>: {<em class="replaceable">col_name</em> <span class="token punctuation">[</span><span class="token punctuation">(</span><em class="replaceable">length</em><span class="token punctuation">)</span><span class="token punctuation">]</span> <span class="token operator">|</span> <span class="token punctuation">(</span><em class="replaceable">expr</em><span class="token punctuation">)</span>} <span class="token punctuation">[</span><span class="token keyword">ASC</span> <span class="token operator">|</span> <span class="token keyword">DESC</span><span class="token punctuation">]</span>
<em class="replaceable">index_type</em>:
<span class="token keyword">USING</span> {<span class="token keyword">BTREE</span> <span class="token operator">|</span> <span class="token keyword">HASH</span>}
<em class="replaceable">index_option</em>: {
<span class="token keyword">KEY_BLOCK_SIZE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token keyword"><em class="replaceable">value</em></span>
<span class="token operator">|</span> <em class="replaceable">index_type</em>
<span class="token operator">|</span> <span class="token keyword">WITH</span> <span class="token keyword">PARSER</span> <em class="replaceable">parser_name</em>
<span class="token operator">|</span> <span class="token keyword">COMMENT</span> <span class="token string">'<em class="replaceable">string</em>'</span>
<span class="token operator">|</span> {<span class="token keyword">VISIBLE</span> <span class="token operator">|</span> <span class="token keyword">INVISIBLE</span>}
}
<em class="replaceable">table_options</em>:
<em class="replaceable">table_option</em> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token punctuation">,</span><span class="token punctuation">]</span> <em class="replaceable">table_option</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<em class="replaceable">table_option</em>: {
<span class="token keyword">AUTOEXTEND_SIZE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token keyword"><em class="replaceable">value</em></span>
<span class="token operator">|</span> <span class="token keyword">AUTO_INCREMENT</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token keyword"><em class="replaceable">value</em></span>
<span class="token operator">|</span> <span class="token keyword">AVG_ROW_LENGTH</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token keyword"><em class="replaceable">value</em></span>
<span class="token operator">|</span> <span class="token punctuation">[</span><span class="token keyword">DEFAULT</span><span class="token punctuation">]</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <em class="replaceable">charset_name</em>
<span class="token operator">|</span> <span class="token keyword">CHECKSUM</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token number">0</span> <span class="token operator">|</span> <span class="token number">1</span>}
<span class="token operator">|</span> <span class="token punctuation">[</span><span class="token keyword">DEFAULT</span><span class="token punctuation">]</span> <span class="token keyword">COLLATE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <em class="replaceable">collation_name</em>
<span class="token operator">|</span> <span class="token keyword">COMMENT</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token string">'<em class="replaceable">string</em>'</span>
<span class="token operator">|</span> <span class="token keyword">COMPRESSION</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token string">'ZLIB'</span> <span class="token operator">|</span> <span class="token string">'LZ4'</span> <span class="token operator">|</span> <span class="token string">'NONE'</span>}
<span class="token operator">|</span> <span class="token keyword">CONNECTION</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token string">'<em class="replaceable">connect_string</em>'</span>
<span class="token operator">|</span> {<span class="token keyword">DATA</span> <span class="token operator">|</span> <span class="token keyword">INDEX</span>} <span class="token keyword">DIRECTORY</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token string">'<em class="replaceable">absolute path to directory</em>'</span>
<span class="token operator">|</span> <span class="token keyword">DELAY_KEY_WRITE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token number">0</span> <span class="token operator">|</span> <span class="token number">1</span>}
<span class="token operator">|</span> <span class="token keyword">ENCRYPTION</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token string">'Y'</span> <span class="token operator">|</span> <span class="token string">'N'</span>}
<span class="token operator">|</span> <span class="token keyword">ENGINE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <em class="replaceable">engine_name</em>
<span class="token operator">|</span> <span class="token keyword">ENGINE_ATTRIBUTE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token string">'<em class="replaceable">string</em>'</span>
<span class="token operator">|</span> <span class="token keyword">INSERT_METHOD</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> { <span class="token keyword">NO</span> <span class="token operator">|</span> <span class="token keyword">FIRST</span> <span class="token operator">|</span> <span class="token keyword">LAST</span> }
<span class="token operator">|</span> <span class="token keyword">KEY_BLOCK_SIZE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token keyword"><em class="replaceable">value</em></span>
<span class="token operator">|</span> <span class="token keyword">MAX_ROWS</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token keyword"><em class="replaceable">value</em></span>
<span class="token operator">|</span> <span class="token keyword">MIN_ROWS</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token keyword"><em class="replaceable">value</em></span>
<span class="token operator">|</span> <span class="token keyword">PACK_KEYS</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token number">0</span> <span class="token operator">|</span> <span class="token number">1</span> <span class="token operator">|</span> <span class="token keyword">DEFAULT</span>}
<span class="token operator">|</span> <span class="token keyword">PASSWORD</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token string">'<em class="replaceable">string</em>'</span>
<span class="token operator">|</span> <span class="token keyword">ROW_FORMAT</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token keyword">DEFAULT</span> <span class="token operator">|</span> <span class="token keyword">DYNAMIC</span> <span class="token operator">|</span> <span class="token keyword">FIXED</span> <span class="token operator">|</span> <span class="token keyword">COMPRESSED</span> <span class="token operator">|</span> <span class="token keyword">REDUNDANT</span> <span class="token operator">|</span> <span class="token keyword">COMPACT</span>}
<span class="token operator">|</span> <span class="token keyword">SECONDARY_ENGINE_ATTRIBUTE</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token string">'<em class="replaceable">string</em>'</span>
<span class="token operator">|</span> <span class="token keyword">STATS_AUTO_RECALC</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token keyword">DEFAULT</span> <span class="token operator">|</span> <span class="token number">0</span> <span class="token operator">|</span> <span class="token number">1</span>}
<span class="token operator">|</span> <span class="token keyword">STATS_PERSISTENT</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> {<span class="token keyword">DEFAULT</span> <span class="token operator">|</span> <span class="token number">0</span> <span class="token operator">|</span> <span class="token number">1</span>}
<span class="token operator">|</span> <span class="token keyword">STATS_SAMPLE_PAGES</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token keyword"><em class="replaceable">value</em></span>
<span class="token operator">|</span> <span class="token keyword">TABLESPACE</span> <em class="replaceable">tablespace_name</em> <span class="token punctuation">[</span><span class="token keyword">STORAGE</span> {<span class="token keyword">DISK</span> <span class="token operator">|</span> <span class="token keyword">MEMORY</span>}<span class="token punctuation">]</span>
<span class="token operator">|</span> <span class="token keyword">UNION</span> <span class="token punctuation">[</span><span class="token operator">=</span><span class="token punctuation">]</span> <span class="token punctuation">(</span><em class="replaceable">tbl_name</em><span class="token punctuation">[</span><span class="token punctuation">,</span><em class="replaceable">tbl_name</em><span class="token punctuation">]</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span>
}
<em class="replaceable">partition_options</em>:
<span class="token punctuation">(</span>see <span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> <span class="token keyword">options</span><span class="token punctuation">)</span></code></pre>
</div>
<p>
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
changes the structure
of a table. For example, you can add or delete columns, create or
destroy indexes, change the type of existing columns, or rename
columns or the table itself. You can also change characteristics
such as the storage engine used for the table or the table
comment.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
To use
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
, you need
<a class="link" href="privileges-provided.html#priv_alter">
<code class="literal">
ALTER
</code>
</a>
,
<a class="link" href="privileges-provided.html#priv_create">
<code class="literal">
CREATE
</code>
</a>
, and
<a class="link" href="privileges-provided.html#priv_insert">
<code class="literal">
INSERT
</code>
</a>
privileges for the
table. Renaming a table requires
<a class="link" href="privileges-provided.html#priv_alter">
<code class="literal">
ALTER
</code>
</a>
and
<a class="link" href="privileges-provided.html#priv_drop">
<code class="literal">
DROP
</code>
</a>
on the old table,
<a class="link" href="privileges-provided.html#priv_alter">
<code class="literal">
ALTER
</code>
</a>
,
<a class="link" href="privileges-provided.html#priv_create">
<code class="literal">
CREATE
</code>
</a>
, and
<a class="link" href="privileges-provided.html#priv_insert">
<code class="literal">
INSERT
</code>
</a>
on the new table.
</p>
</li>
<li class="listitem">
<p>
Following the table name, specify the alterations to be made.
If none are given,
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
does nothing.
</p>
</li>
<li class="listitem">
<p>
The syntax for many of the permissible alterations is similar
to clauses of the
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
statement.
<em class="replaceable">
<code>
column_definition
</code>
</em>
clauses use the same syntax for
<code class="literal">
ADD
</code>
and
<code class="literal">
CHANGE
</code>
as for
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE
TABLE
</code>
</a>
. For more information, see
<a class="xref" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
Section 15.1.20, “CREATE TABLE Statement”
</a>
.
</p>
</li>
<li class="listitem">
<p>
The word
<code class="literal">
COLUMN
</code>
is optional and can be
omitted, except for
<code class="literal">
RENAME COLUMN
</code>
(to
distinguish a column-renaming operation from the
<code class="literal">
RENAME
</code>
table-renaming operation).
</p>
</li>
<li class="listitem">
<p>
Multiple
<code class="literal">
ADD
</code>
,
<code class="literal">
ALTER
</code>
,
<code class="literal">
DROP
</code>
, and
<code class="literal">
CHANGE
</code>
clauses
are permitted in a single
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
statement, separated by commas. This is a
MySQL extension to standard SQL, which permits only one of
each clause per
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
statement. For example, to drop multiple columns in a single
statement, do this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa72565496"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t2 <span class="token keyword">DROP</span> <span class="token keyword">COLUMN</span> c<span class="token punctuation">,</span> <span class="token keyword">DROP</span> <span class="token keyword">COLUMN</span> d<span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
If a storage engine does not support an attempted
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
operation, a
warning may result. Such warnings can be displayed with
<a class="link" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
<code class="literal">
SHOW WARNINGS
</code>
</a>
. See
<a class="xref" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
Section 15.7.7.42, “SHOW WARNINGS Statement”
</a>
. For information on
troubleshooting
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
,
see
<a class="xref" href="alter-table-problems.html" title="B.3.6.1 Problems with ALTER TABLE">
Section B.3.6.1, “Problems with ALTER TABLE”
</a>
.
</p>
</li>
<li class="listitem">
<p>
For information about generated columns, see
<a class="xref" href="alter-table-generated-columns.html" title="15.1.9.2 ALTER TABLE and Generated Columns">
Section 15.1.9.2, “ALTER TABLE and Generated Columns”
</a>
.
</p>
</li>
<li class="listitem">
<p>
For usage examples, see
<a class="xref" href="alter-table-examples.html" title="15.1.9.3 ALTER TABLE Examples">
Section 15.1.9.3, “ALTER TABLE Examples”
</a>
.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
<code class="literal">
InnoDB
</code>
</a>
supports addition of
multi-valued indexes on JSON columns using a
<em class="replaceable">
<code>
key_part
</code>
</em>
specification can take the
form
<code class="literal">
(CAST
<em class="replaceable">
<code>
json_path
</code>
</em>
AS
<em class="replaceable">
<code>
type
</code>
</em>
ARRAY)
</code>
. See
<a class="xref" href="create-index.html#create-index-multi-valued" title="Multi-Valued Indexes">
Multi-Valued Indexes
</a>
, for detailed
information regarding multi-valued index creation and usage
of, as well as restrictions and limitations on multi-valued
indexes.
</p>
</li>
<li class="listitem">
<p>
With the
<a class="ulink" href="/doc/c-api/8.4/en/mysql-info.html" target="_top">
<code class="literal">
mysql_info()
</code>
</a>
C API
function, you can find out how many rows were copied by
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
. See
<a class="ulink" href="/doc/c-api/8.4/en/mysql-info.html" target="_top">
mysql_info()
</a>
.
</p>
<a class="indexterm" name="idm46045189467616">
</a>
</li>
</ul>
</div>
<p>
There are several additional aspects to the
<code class="literal">
ALTER
TABLE
</code>
statement, described under the following topics in
this section:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="xref" href="alter-table.html#alter-table-options" title="Table Options">
Table Options
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-table.html#alter-table-performance" title="Performance and Space Requirements">
Performance and Space Requirements
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-table.html#alter-table-concurrency" title="Concurrency Control">
Concurrency Control
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-table.html#alter-table-add-drop-column" title="Adding and Dropping Columns">
Adding and Dropping Columns
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-table.html#alter-table-redefine-column" title="Renaming, Redefining, and Reordering Columns">
Renaming, Redefining, and Reordering Columns
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-table.html#alter-table-index" title="Primary Keys and Indexes">
Primary Keys and Indexes
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-table.html#alter-table-foreign-key" title="Foreign Keys and Other Constraints">
Foreign Keys and Other Constraints
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-table.html#alter-table-character-set" title="Changing the Character Set">
Changing the Character Set
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-table.html#alter-table-import" title="Importing InnoDB Tables">
Importing InnoDB Tables
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-table.html#alter-table-row-order" title="Row Order for MyISAM Tables">
Row Order for MyISAM Tables
</a>
</p>
</li>
<li class="listitem">
<p>
<a class="xref" href="alter-table.html#alter-table-partition-options" title="Partitioning Options">
Partitioning Options
</a>
</p>
</li>
</ul>
</div>
<h4>
<a name="alter-table-options">
</a>
Table Options
</h4>
<p>
<em class="replaceable">
<code>
table_options
</code>
</em>
signifies table options
of the kind that can be used in the
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE
TABLE
</code>
</a>
statement, such as
<code class="literal">
ENGINE
</code>
,
<code class="literal">
AUTO_INCREMENT
</code>
,
<code class="literal">
AVG_ROW_LENGTH
</code>
,
<code class="literal">
MAX_ROWS
</code>
,
<code class="literal">
ROW_FORMAT
</code>
, or
<code class="literal">
TABLESPACE
</code>
.
</p>
<p>
For descriptions of all table options, see
<a class="xref" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
Section 15.1.20, “CREATE TABLE Statement”
</a>
. However,
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
ignores
<code class="literal">
DATA
DIRECTORY
</code>
and
<code class="literal">
INDEX DIRECTORY
</code>
when
given as table options.
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
permits them only as partitioning options, and requires that you
have the
<code class="literal">
FILE
</code>
privilege.
</p>
<p>
Use of table options with
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
provides a convenient way of altering single table
characteristics. For example:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
If
<code class="literal">
t1
</code>
is currently not an
<code class="literal">
InnoDB
</code>
table, this statement changes its
storage engine to
<code class="literal">
InnoDB
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa3578747"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">ENGINE</span> <span class="token operator">=</span> InnoDB<span class="token punctuation">;</span></code></pre>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
See
<a class="xref" href="converting-tables-to-innodb.html" title="17.6.1.5 Converting Tables from MyISAM to InnoDB">
Section 17.6.1.5, “Converting Tables from MyISAM to InnoDB”
</a>
for
considerations when switching tables to the
<code class="literal">
InnoDB
</code>
storage engine.
</p>
</li>
<li class="listitem">
<p>
When you specify an
<code class="literal">
ENGINE
</code>
clause,
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
rebuilds the
table. This is true even if the table already has the
specified storage engine.
</p>
</li>
<li class="listitem">
<p>
Running
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
<em class="replaceable">
<code>
tbl_name
</code>
</em>
ENGINE=INNODB
</code>
</a>
on an existing
<code class="literal">
InnoDB
</code>
table performs a
<span class="quote">
“
<span class="quote">
null
</span>
”
</span>
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
operation, which can be used to defragment
an
<code class="literal">
InnoDB
</code>
table, as described in
<a class="xref" href="innodb-file-defragmenting.html" title="17.11.4 Defragmenting a Table">
Section 17.11.4, “Defragmenting a Table”
</a>
. Running
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
<em class="replaceable">
<code>
tbl_name
</code>
</em>
FORCE
</code>
</a>
on an
<code class="literal">
InnoDB
</code>
table performs the same
function.
</p>
</li>
<li class="listitem">
<p>
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
<em class="replaceable">
<code>
tbl_name
</code>
</em>
ENGINE=INNODB
</code>
</a>
and
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
<em class="replaceable">
<code>
tbl_name
</code>
</em>
FORCE
</code>
</a>
use
<a class="link" href="innodb-online-ddl.html" title="17.12 InnoDB and Online DDL">
online DDL
</a>
. For
more information, see
<a class="xref" href="innodb-online-ddl.html" title="17.12 InnoDB and Online DDL">
Section 17.12, “InnoDB and Online DDL”
</a>
.
</p>
</li>
<li class="listitem">
<p>
The outcome of attempting to change the storage engine of
a table is affected by whether the desired storage engine
is available and the setting of the
<a class="link" href="sql-mode.html#sqlmode_no_engine_substitution">
<code class="literal">
NO_ENGINE_SUBSTITUTION
</code>
</a>
SQL mode, as described in
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
.
</p>
</li>
<li class="listitem">
<p>
To prevent inadvertent loss of data,
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
cannot be used
to change the storage engine of a table to
<code class="literal">
MERGE
</code>
or
<code class="literal">
BLACKHOLE
</code>
.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
To change the
<code class="literal">
InnoDB
</code>
table to use
compressed row-storage format:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa79985828"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">ROW_FORMAT</span> <span class="token operator">=</span> <span class="token keyword">COMPRESSED</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
The
<code class="literal">
ENCRYPTION
</code>
clause enables or disables
page-level data encryption for an
<code class="literal">
InnoDB
</code>
table. A keyring plugin must be installed and configured to
enable encryption.
</p>
<p>
If the
<a class="link" href="server-system-variables.html#sysvar_table_encryption_privilege_check">
<code class="literal">
table_encryption_privilege_check
</code>
</a>
variable is enabled, the
<a class="link" href="privileges-provided.html#priv_table-encryption-admin">
<code class="literal">
TABLE_ENCRYPTION_ADMIN
</code>
</a>
privilege is required to use an
<code class="literal">
ENCRYPTION
</code>
clause with a setting that differs from the default schema
encryption setting.
</p>
<p>
<code class="literal">
ENCRYPTION
</code>
is also supported for tables
residing in general tablespaces.
</p>
<p>
For tables that reside in general tablespaces, table and
tablespace encryption must match.
</p>
<p>
The
<code class="literal">
ENCRYPTION
</code>
option is supported only by
the
<code class="literal">
InnoDB
</code>
storage engine; thus it works
only if the table already uses
<code class="literal">
InnoDB
</code>
(and
you do not change the table's storage engine), or if the
<code class="literal">
ALTER TABLE
</code>
statement also specifies
<code class="literal">
ENGINE=InnoDB
</code>
. Otherwise the statement is
rejected with
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_check_not_implemented" target="_top">
<code class="literal">
ER_CHECK_NOT_IMPLEMENTED
</code>
</a>
.
</p>
<p>
Altering table encryption by moving a table to a different
tablespace or changing the storage engine is not permitted
without explicitly specifying an
<code class="literal">
ENCRYPTION
</code>
clause.
</p>
<p>
Specifying an
<code class="literal">
ENCRYPTION
</code>
clause with a
value other than
<code class="literal">
'N'
</code>
or
<code class="literal">
''
</code>
is not permitted if the table uses a
storage engine that does not support encryption. Attempting to
create a table without an
<code class="literal">
ENCRYPTION
</code>
clause
in an encryption-enabled schema using a storage engine that
does not support encryption is also not permitted.
</p>
<p>
For more information, see
<a class="xref" href="innodb-data-encryption.html" title="17.13 InnoDB Data-at-Rest Encryption">
Section 17.13, “InnoDB Data-at-Rest Encryption”
</a>
.
</p>
</li>
<li class="listitem">
<p>
To reset the current auto-increment value:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa50932411"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">AUTO_INCREMENT</span> <span class="token operator">=</span> <span class="token number">13</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
You cannot reset the counter to a value less than or equal to
the value that is currently in use. For both
<code class="literal">
InnoDB
</code>
and
<code class="literal">
MyISAM
</code>
, if
the value is less than or equal to the maximum value currently
in the
<code class="literal">
AUTO_INCREMENT
</code>
column, the value is
reset to the current maximum
<code class="literal">
AUTO_INCREMENT
</code>
column value plus one.
</p>
</li>
<li class="listitem">
<p>
To change the default table character set:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa77478368"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <span class="token operator">=</span> utf8mb4<span class="token punctuation">;</span></code></pre>
</div>
<p>
See also
<a class="xref" href="alter-table.html#alter-table-character-set" title="Changing the Character Set">
Changing the Character Set
</a>
.
</p>
</li>
<li class="listitem">
<p>
To add (or change) a table comment:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa1024643"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">COMMENT</span> <span class="token operator">=</span> <span class="token string">'New table comment'</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Use
<code class="literal">
ALTER TABLE
</code>
with the
<code class="literal">
TABLESPACE
</code>
option to move
<code class="literal">
InnoDB
</code>
tables between existing
<a class="link" href="glossary.html#glos_general_tablespace" title="general tablespace">
general
tablespaces
</a>
,
<a class="link" href="glossary.html#glos_file_per_table" title="file-per-table">
file-per-table
</a>
tablespaces, and the
<a class="link" href="glossary.html#glos_system_tablespace" title="system tablespace">
system
tablespace
</a>
. See
<a class="xref" href="general-tablespaces.html#general-tablespaces-moving-non-partitioned-tables" title="Moving Tables Between Tablespaces Using ALTER TABLE">
Moving Tables Between Tablespaces Using ALTER TABLE
</a>
.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
<code class="literal">
ALTER TABLE ... TABLESPACE
</code>
operations
always cause a full table rebuild, even if the
<code class="literal">
TABLESPACE
</code>
attribute has not changed
from its previous value.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ALTER TABLE ... TABLESPACE
</code>
syntax does
not support moving a table from a temporary tablespace to
a persistent tablespace.
</p>
</li>
<li class="listitem">
<p>
The
<code class="literal">
DATA DIRECTORY
</code>
clause, which is
supported with
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
... TABLESPACE
</code>
</a>
, is not supported with
<code class="literal">
ALTER TABLE ... TABLESPACE
</code>
, and is
ignored if specified.
</p>
</li>
<li class="listitem">
<p>
For more information about the capabilities and
limitations of the
<code class="literal">
TABLESPACE
</code>
option,
see
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
MySQL NDB Cluster 8.4 supports setting
<code class="literal">
NDB_TABLE
</code>
options for controlling a
table's partition balance (fragment count type),
read-from-any-replica capability, full replication, or any
combination of these, as part of the table comment for an
<code class="literal">
ALTER TABLE
</code>
statement in the same manner as
for
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
, as shown in
this example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa47427485"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">COMMENT</span> <span class="token operator">=</span> <span class="token string">"NDB_TABLE=READ_BACKUP=0,PARTITION_BALANCE=FOR_RA_BY_NODE"</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
It is also possible to set
<code class="literal">
NDB_COMMENT
</code>
options for columns of
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
tables
as part of an
<code class="literal">
ALTER TABLE
</code>
statement, like
this one:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa79404315"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1
<span class="token keyword">CHANGE</span> <span class="token keyword">COLUMN</span> c1 c1 <span class="token datatype">BLOB</span>
<span class="token keyword">COMMENT</span> <span class="token operator">=</span> <span class="token string">'NDB_COLUMN=BLOB_INLINE_SIZE=4096,MAX_BLOB_PART_SIZE'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Bear in mind that
<code class="literal">
ALTER TABLE ... COMMENT
...
</code>
discards any existing comment for the table. See
<a class="xref" href="create-table.html#create-table-comment-ndb-table-options" title="Setting NDB_TABLE options">
Setting NDB_TABLE options
</a>
, for
additional information and examples.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
ENGINE_ATTRIBUTE
</code>
and
<code class="literal">
SECONDARY_ENGINE_ATTRIBUTE
</code>
options are used
to specify table, column, and index attributes for primary and
secondary storage engines. These options are reserved for
future use. Index attributes cannot be altered. An index must
be dropped and added back with the desired change, which can
be performed in a single
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
statement.
</p>
</li>
</ul>
</div>
<p>
To verify that the table options were changed as intended, use
<a class="link" href="show-create-table.html" title="15.7.7.11 SHOW CREATE TABLE Statement">
<code class="literal">
SHOW CREATE TABLE
</code>
</a>
, or query the
Information Schema
<a class="link" href="information-schema-tables-table.html" title="28.3.38 The INFORMATION_SCHEMA TABLES Table">
<code class="literal">
TABLES
</code>
</a>
table.
</p>
<h4>
<a name="alter-table-performance">
</a>
Performance and Space Requirements
</h4>
<p>
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
operations are
processed using one of the following algorithms:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
COPY
</code>
: Operations are performed on a copy of
the original table, and table data is copied from the original
table to the new table row by row. Concurrent DML is not
permitted.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
INPLACE
</code>
: Operations avoid copying table
data but may rebuild the table in place. An exclusive metadata
lock on the table may be taken briefly during preparation and
execution phases of the operation. Typically, concurrent DML
is supported.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
INSTANT
</code>
: Operations only modify metadata in
the data dictionary. An exclusive metadata lock on the table
may be taken briefly during the execution phase of the
operation. Table data is unaffected, making operations
instantaneous. Concurrent DML is permitted.
</p>
</li>
</ul>
</div>
<p>
For tables using the
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
storage
engine, these algorithms work as follows:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
COPY
</code>
:
<code class="literal">
NDB
</code>
creates a copy
of the table and alters it; the NDB Cluster handler then
copies the data between the old and new versions of the table.
Subsequently,
<code class="literal">
NDB
</code>
deletes the old table and
renames the new one.
</p>
<p>
This is sometimes also referred to as a
<span class="quote">
“
<span class="quote">
copying
</span>
”
</span>
or
<span class="quote">
“
<span class="quote">
offline
</span>
”
</span>
<code class="literal">
ALTER TABLE
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
INPLACE
</code>
: The data nodes make the required
changes; the NDB Cluster handler does not copy data or
otherwise take part.
</p>
<p>
This is sometimes also referred to as a
<span class="quote">
“
<span class="quote">
non-copying
</span>
”
</span>
or
<span class="quote">
“
<span class="quote">
online
</span>
”
</span>
<code class="literal">
ALTER TABLE
</code>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
INSTANT
</code>
: Not supported by
<code class="literal">
NDB
</code>
.
</p>
</li>
</ul>
</div>
<p>
See
<a class="xref" href="mysql-cluster-online-operations.html" title="25.6.12 Online Operations with ALTER TABLE in NDB Cluster">
Section 25.6.12, “Online Operations with ALTER TABLE in NDB Cluster”
</a>
, for more
information.
</p>
<p>
The
<code class="literal">
ALGORITHM
</code>
clause is optional. If the
<code class="literal">
ALGORITHM
</code>
clause is omitted, MySQL uses
<code class="literal">
ALGORITHM=INSTANT
</code>
for storage engines and
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
clauses that support
it. Otherwise,
<code class="literal">
ALGORITHM=INPLACE
</code>
is used. If
<code class="literal">
ALGORITHM=INPLACE
</code>
is not supported,
<code class="literal">
ALGORITHM=COPY
</code>
is used.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
After adding a column to a partitioned table using
<code class="literal">
ALGORITHM=INSTANT
</code>
, it is no longer possible
to perform
<a class="link" href="alter-table-partition-operations.html" title="15.1.9.1 ALTER TABLE Partition Operations">
<code class="literal">
ALTER
TABLE ... EXCHANGE PARTITION
</code>
</a>
on the table.
</p>
</div>
<p>
Specifying an
<code class="literal">
ALGORITHM
</code>
clause requires the
operation to use the specified algorithm for clauses and storage
engines that support it, or fail with an error otherwise.
Specifying
<code class="literal">
ALGORITHM=DEFAULT
</code>
is the same as
omitting the
<code class="literal">
ALGORITHM
</code>
clause.
</p>
<p>
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
operations that use the
<code class="literal">
COPY
</code>
algorithm wait for other operations that
are modifying the table to complete. After alterations are applied
to the table copy, data is copied over, the original table is
deleted, and the table copy is renamed to the name of the original
table. While the
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
operation executes, the original table is readable by other
sessions (with the exception noted shortly). Updates and writes to
the table started after the
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
operation begins are stalled until the new table
is ready, then are automatically redirected to the new table. The
temporary copy of the table is created in the database directory
of the original table unless it is a
<code class="literal">
RENAME TO
</code>
operation that moves the table to a database that resides in a
different directory.
</p>
<p>
The exception referred to earlier is that
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
blocks reads (not just
writes) at the point where it is ready to clear outdated table
structures from the table and table definition caches. At this
point, it must acquire an exclusive lock. To do so, it waits for
current readers to finish, and blocks new reads and writes.
</p>
<p>
An
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
operation that uses
the
<code class="literal">
COPY
</code>
algorithm prevents concurrent DML
operations. Concurrent queries are still allowed. That is, a
table-copying operation always includes at least the concurrency
restrictions of
<code class="literal">
LOCK=SHARED
</code>
(allow queries but
not DML). You can further restrict concurrency for operations that
support the
<code class="literal">
LOCK
</code>
clause by specifying
<code class="literal">
LOCK=EXCLUSIVE
</code>
, which prevents DML and queries.
For more information, see
<a class="xref" href="alter-table.html#alter-table-concurrency" title="Concurrency Control">
Concurrency Control
</a>
.
</p>
<p>
To force use of the
<code class="literal">
COPY
</code>
algorithm for an
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
operation that would
otherwise not use it, specify
<code class="literal">
ALGORITHM=COPY
</code>
or
enable the
<a class="link" href="server-system-variables.html#sysvar_old_alter_table">
<code class="literal">
old_alter_table
</code>
</a>
system
variable. If there is a conflict between the
<code class="literal">
old_alter_table
</code>
setting and an
<code class="literal">
ALGORITHM
</code>
clause with a value other than
<code class="literal">
DEFAULT
</code>
, the
<code class="literal">
ALGORITHM
</code>
clause takes precedence.
</p>
<p>
For
<code class="literal">
InnoDB
</code>
tables, an
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
operation that uses the
<code class="literal">
COPY
</code>
algorithm on a table that resides in a
<a class="link" href="glossary.html#glos_shared_tablespace" title="shared tablespace">
shared tablespace
</a>
can increase the amount of space used by the tablespace. Such
operations require as much additional space as the data in the
table plus indexes. For a table residing in a shared tablespace,
the additional space used during the operation is not released
back to the operating system as it is for a table that resides in
a
<a class="link" href="glossary.html#glos_file_per_table" title="file-per-table">
file-per-table
</a>
tablespace.
</p>
<p>
For information about space requirements for online DDL
operations, see
<a class="xref" href="innodb-online-ddl-space-requirements.html" title="17.12.3 Online DDL Space Requirements">
Section 17.12.3, “Online DDL Space Requirements”
</a>
.
</p>
<p>
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
operations that support
the
<code class="literal">
INPLACE
</code>
algorithm include:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
ALTER TABLE
</code>
operations supported by the
<code class="literal">
InnoDB
</code>
<a class="link" href="glossary.html#glos_online_ddl" title="online DDL">
online DDL
</a>
feature. See
<a class="xref" href="innodb-online-ddl-operations.html" title="17.12.1 Online DDL Operations">
Section 17.12.1, “Online DDL Operations”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Renaming a table. MySQL renames files that correspond to the
table
<em class="replaceable">
<code>
tbl_name
</code>
</em>
without making a
copy. (You can also use the
<a class="link" href="rename-table.html" title="15.1.36 RENAME TABLE Statement">
<code class="literal">
RENAME
TABLE
</code>
</a>
statement to rename tables. See
<a class="xref" href="rename-table.html" title="15.1.36 RENAME TABLE Statement">
Section 15.1.36, “RENAME TABLE Statement”
</a>
.) Privileges granted
specifically for the renamed table are not migrated to the new
name. They must be changed manually.
</p>
</li>
<li class="listitem">
<p>
Operations that modify table metadata only. These operations
are immediate because the server does not touch table
contents. Metadata-only operations include:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Renaming a column. In NDB Cluster, this operation can also
be performed online.
</p>
</li>
<li class="listitem">
<p>
Changing the default value of a column (except for
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
tables).
</p>
</li>
<li class="listitem">
<p>
Modifying the definition of an
<a class="link" href="enum.html" title="13.3.5 The ENUM Type">
<code class="literal">
ENUM
</code>
</a>
or
<a class="link" href="set.html" title="13.3.6 The SET Type">
<code class="literal">
SET
</code>
</a>
column by adding new
enumeration or set members to the
<span class="emphasis">
<em>
end
</em>
</span>
of the list of valid member values, as long as the storage
size of the data type does not change. For example, adding
a member to a
<a class="link" href="set.html" title="13.3.6 The SET Type">
<code class="literal">
SET
</code>
</a>
column
that has 8 members changes the required storage per value
from 1 byte to 2 bytes; this requires a table copy. Adding
members in the middle of the list causes renumbering of
existing members, which requires a table copy.
</p>
</li>
<li class="listitem">
<p>
Changing the definition of a spatial column to remove the
<code class="literal">
SRID
</code>
attribute. (Adding or changing an
<code class="literal">
SRID
</code>
attribute requires a rebuild, and
cannot be done in place, because the server must verify
that all values have the specified
<code class="literal">
SRID
</code>
value.)
</p>
</li>
<li class="listitem">
<p>
Changing a column character set, when these conditions
apply:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: square; ">
<li class="listitem">
<p>
The column data type is
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
,
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
, a
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
type, or
<a class="link" href="enum.html" title="13.3.5 The ENUM Type">
<code class="literal">
ENUM
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
The character set change is from
<code class="literal">
utf8mb3
</code>
to
<code class="literal">
utf8mb4
</code>
, or any character set to
<code class="literal">
binary
</code>
.
</p>
</li>
<li class="listitem">
<p>
There is no index on the column.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Changing a generated column, when these conditions apply:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: square; ">
<li class="listitem">
<p>
For
<code class="literal">
InnoDB
</code>
tables, statements that
modify generated stored columns but do not change
their type, expression, or nullability.
</p>
</li>
<li class="listitem">
<p>
For non-
<code class="literal">
InnoDB
</code>
tables, statements
that modify generated stored or virtual columns but do
not change their type, expression, or nullability.
</p>
</li>
</ul>
</div>
<p>
An example of such a change is a change to the column
comment.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
Renaming an index.
</p>
</li>
<li class="listitem">
<p>
Adding or dropping a secondary index, for
<a class="link" href="innodb-storage-engine.html" title="Chapter 17 The InnoDB Storage Engine">
<code class="literal">
InnoDB
</code>
</a>
and
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
tables. See
<a class="xref" href="innodb-online-ddl-operations.html" title="17.12.1 Online DDL Operations">
Section 17.12.1, “Online DDL Operations”
</a>
.
</p>
</li>
<li class="listitem">
<p>
For
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
tables, operations that
add and drop indexes on variable-width columns. These
operations occur online, without table copying and without
blocking concurrent DML actions for most of their duration.
See
<a class="xref" href="mysql-cluster-online-operations.html" title="25.6.12 Online Operations with ALTER TABLE in NDB Cluster">
Section 25.6.12, “Online Operations with ALTER TABLE in NDB Cluster”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Modifying index visibility with an
<code class="literal">
ALTER
INDEX
</code>
operation.
</p>
</li>
<li class="listitem">
<p>
Column modifications of tables containing generated columns
that depend on columns with a
<code class="literal">
DEFAULT
</code>
value
if the modified columns are not involved in the generated
column expressions. For example, changing the
<code class="literal">
NULL
</code>
property of a separate column can be
done in place without a table rebuild.
</p>
</li>
</ul>
</div>
<p>
<code class="literal">
ALTER TABLE
</code>
operations that support the
<code class="literal">
INSTANT
</code>
algorithm include:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Adding a column. This feature is referred to as
<span class="quote">
“
<span class="quote">
Instant
<code class="literal">
ADD COLUMN
</code>
</span>
”
</span>
. Limitations apply. See
<a class="xref" href="innodb-online-ddl-operations.html" title="17.12.1 Online DDL Operations">
Section 17.12.1, “Online DDL Operations”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Dropping a column. This feature is referred to as
<span class="quote">
“
<span class="quote">
Instant
<code class="literal">
DROP COLUMN
</code>
</span>
”
</span>
.
Limitations apply. See
<a class="xref" href="innodb-online-ddl-operations.html" title="17.12.1 Online DDL Operations">
Section 17.12.1, “Online DDL Operations”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Adding or dropping a virtual column.
</p>
</li>
<li class="listitem">
<p>
Adding or dropping a column default value.
</p>
</li>
<li class="listitem">
<p>
Modifying the definition of an
<a class="link" href="enum.html" title="13.3.5 The ENUM Type">
<code class="literal">
ENUM
</code>
</a>
or
<a class="link" href="set.html" title="13.3.6 The SET Type">
<code class="literal">
SET
</code>
</a>
column. The same
restrictions apply as described above for
<code class="literal">
ALGORITHM=INSTANT
</code>
.
</p>
</li>
<li class="listitem">
<p>
Changing the index type.
</p>
</li>
<li class="listitem">
<p>
Renaming a table. The same restrictions apply as described
above for
<code class="literal">
ALGORITHM=INSTANT
</code>
.
</p>
</li>
</ul>
</div>
<p>
For more information about operations that support
<code class="literal">
ALGORITHM=INSTANT
</code>
, see
<a class="xref" href="innodb-online-ddl-operations.html" title="17.12.1 Online DDL Operations">
Section 17.12.1, “Online DDL Operations”
</a>
.
</p>
<p>
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
upgrades MySQL 5.5
temporal columns to 5.6 format for
<code class="literal">
ADD COLUMN
</code>
,
<code class="literal">
CHANGE COLUMN
</code>
,
<code class="literal">
MODIFY
COLUMN
</code>
,
<code class="literal">
ADD INDEX
</code>
, and
<code class="literal">
FORCE
</code>
operations. This conversion cannot be
done using the
<code class="literal">
INPLACE
</code>
algorithm because the
table must be rebuilt, so specifying
<code class="literal">
ALGORITHM=INPLACE
</code>
in these cases results in an
error. Specify
<code class="literal">
ALGORITHM=COPY
</code>
if necessary.
</p>
<p>
If an
<code class="literal">
ALTER TABLE
</code>
operation on a multicolumn
index used to partition a table by
<code class="literal">
KEY
</code>
changes
the order of the columns, it can only be performed using
<code class="literal">
ALGORITHM=COPY
</code>
.
</p>
<p>
The
<code class="literal">
WITHOUT VALIDATION
</code>
and
<code class="literal">
WITH
VALIDATION
</code>
clauses affect whether
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
performs an in-place
operation for
<a class="link" href="glossary.html#glos_virtual_generated_column" title="virtual generated column">
virtual generated
column
</a>
modifications. See
<a class="xref" href="alter-table-generated-columns.html" title="15.1.9.2 ALTER TABLE and Generated Columns">
Section 15.1.9.2, “ALTER TABLE and Generated Columns”
</a>
.
</p>
<p>
NDB Cluster 8.4 supports online operations using the
same
<code class="literal">
ALGORITHM=INPLACE
</code>
syntax used with the
standard MySQL Server.
<code class="literal">
NDB
</code>
does not allow
changing a tablespace online. See
<a class="xref" href="mysql-cluster-online-operations.html" title="25.6.12 Online Operations with ALTER TABLE in NDB Cluster">
Section 25.6.12, “Online Operations with ALTER TABLE in NDB Cluster”
</a>
, for more
information.
</p>
<p>
When performing a copying
<code class="literal">
ALTER TABLE
</code>
,
<code class="literal">
NDB
</code>
checks to ensure that no concurrent writes
have been made to the affected table. If it finds that any have
been made,
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
rejects the
<code class="literal">
ALTER TABLE
</code>
statement and raises
<a class="ulink" href="/doc/mysql-errors/8.4/en/server-error-reference.html#error_er_table_def_changed" target="_top">
<code class="literal">
ER_TABLE_DEF_CHANGED
</code>
</a>
.
</p>
<p>
<code class="literal">
ALTER TABLE
</code>
with
<code class="literal">
DISCARD ... PARTITION
... TABLESPACE
</code>
or
<code class="literal">
IMPORT ... PARTITION ...
TABLESPACE
</code>
does not create any temporary tables or
temporary partition files.
</p>
<p>
<code class="literal">
ALTER TABLE
</code>
with
<code class="literal">
ADD
PARTITION
</code>
,
<code class="literal">
DROP PARTITION
</code>
,
<code class="literal">
COALESCE PARTITION
</code>
,
<code class="literal">
REBUILD
PARTITION
</code>
, or
<code class="literal">
REORGANIZE PARTITION
</code>
does not create temporary tables (except when used with
<a class="link" href="mysql-cluster.html" title="Chapter 25 MySQL NDB Cluster 8.4">
<code class="literal">
NDB
</code>
</a>
tables); however, these
operations can and do create temporary partition files.
</p>
<p>
<code class="literal">
ADD
</code>
or
<code class="literal">
DROP
</code>
operations for
<code class="literal">
RANGE
</code>
or
<code class="literal">
LIST
</code>
partitions are
immediate operations or nearly so.
<code class="literal">
ADD
</code>
or
<code class="literal">
COALESCE
</code>
operations for
<code class="literal">
HASH
</code>
or
<code class="literal">
KEY
</code>
partitions copy data between all
partitions, unless
<code class="literal">
LINEAR HASH
</code>
or
<code class="literal">
LINEAR KEY
</code>
was used; this is effectively the
same as creating a new table, although the
<code class="literal">
ADD
</code>
or
<code class="literal">
COALESCE
</code>
operation is performed partition by
partition.
<code class="literal">
REORGANIZE
</code>
operations copy only
changed partitions and do not touch unchanged ones.
</p>
<p>
For
<code class="literal">
MyISAM
</code>
tables, you can speed up index
re-creation (the slowest part of the alteration process) by
setting the
<a class="link" href="server-system-variables.html#sysvar_myisam_sort_buffer_size">
<code class="literal">
myisam_sort_buffer_size
</code>
</a>
system
variable to a high value.
</p>
<h4>
<a name="alter-table-concurrency">
</a>
Concurrency Control
</h4>
<p>
For
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
operations that
support it, you can use the
<code class="literal">
LOCK
</code>
clause to
control the level of concurrent reads and writes on a table while
it is being altered. Specifying a non-default value for this
clause enables you to require a certain amount of concurrent
access or exclusivity during the alter operation, and halts the
operation if the requested degree of locking is not available.
</p>
<p>
Only
<code class="literal">
LOCK = DEFAULT
</code>
is permitted for operations
that use
<code class="literal">
ALGORITHM=INSTANT
</code>
. The other
<code class="literal">
LOCK
</code>
clause parameters are not applicable.
</p>
<p>
The parameters for the
<code class="literal">
LOCK
</code>
clause are:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
LOCK = DEFAULT
</code>
</p>
<p>
Maximum level of concurrency for the given
<code class="literal">
ALGORITHM
</code>
clause (if any) and
<code class="literal">
ALTER TABLE
</code>
operation: Permit concurrent
reads and writes if supported. If not, permit concurrent reads
if supported. If not, enforce exclusive access.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
LOCK = NONE
</code>
</p>
<p>
If supported, permit concurrent reads and writes. Otherwise,
an error occurs.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
LOCK = SHARED
</code>
</p>
<p>
If supported, permit concurrent reads but block writes. Writes
are blocked even if concurrent writes are supported by the
storage engine for the given
<code class="literal">
ALGORITHM
</code>
clause (if any) and
<code class="literal">
ALTER TABLE
</code>
operation.
If concurrent reads are not supported, an error occurs.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
LOCK = EXCLUSIVE
</code>
</p>
<p>
Enforce exclusive access. This is done even if concurrent
reads/writes are supported by the storage engine for the given
<code class="literal">
ALGORITHM
</code>
clause (if any) and
<code class="literal">
ALTER TABLE
</code>
operation.
</p>
</li>
</ul>
</div>
<h4>
<a name="alter-table-add-drop-column">
</a>
Adding and Dropping Columns
</h4>
<p>
Use
<code class="literal">
ADD
</code>
to add new columns to a table, and
<code class="literal">
DROP
</code>
to remove existing columns.
<code class="literal">
DROP
<em class="replaceable">
<code>
col_name
</code>
</em>
</code>
is a MySQL extension
to standard SQL.
</p>
<p>
To add a column at a specific position within a table row, use
<code class="literal">
FIRST
</code>
or
<code class="literal">
AFTER
<em class="replaceable">
<code>
col_name
</code>
</em>
</code>
. The default is to
add the column last.
</p>
<p>
If a table contains only one column, the column cannot be dropped.
If what you intend is to remove the table, use the
<a class="link" href="drop-table.html" title="15.1.32 DROP TABLE Statement">
<code class="literal">
DROP TABLE
</code>
</a>
statement instead.
</p>
<p>
If columns are dropped from a table, the columns are also removed
from any index of which they are a part. If all columns that make
up an index are dropped, the index is dropped as well. If you use
<code class="literal">
CHANGE
</code>
or
<code class="literal">
MODIFY
</code>
to shorten
a column for which an index exists on the column, and the
resulting column length is less than the index length, MySQL
shortens the index automatically.
</p>
<p>
For
<code class="literal">
ALTER TABLE ... ADD
</code>
, if the column has an
expression default value that uses a nondeterministic function,
the statement may produce a warning or error. For further
information, see
<a class="xref" href="data-type-defaults.html" title="13.6 Data Type Default Values">
Section 13.6, “Data Type Default Values”
</a>
, and
<a class="xref" href="replication-gtids-restrictions.html" title="19.1.3.7 Restrictions on Replication with GTIDs">
Section 19.1.3.7, “Restrictions on Replication with GTIDs”
</a>
.
</p>
<h4>
<a name="alter-table-redefine-column">
</a>
Renaming, Redefining, and Reordering Columns
</h4>
<a class="indexterm" name="idm46045189128768">
</a>
<a class="indexterm" name="idm46045189127280">
</a>
<a class="indexterm" name="idm46045189125792">
</a>
<a class="indexterm" name="idm46045189124304">
</a>
<p>
The
<code class="literal">
CHANGE
</code>
,
<code class="literal">
MODIFY
</code>
,
<code class="literal">
RENAME COLUMN
</code>
, and
<code class="literal">
ALTER
</code>
clauses enable the names and definitions of existing columns to be
altered. They have these comparative characteristics:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
CHANGE
</code>
:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Can rename a column and change its definition, or both.
</p>
</li>
<li class="listitem">
<p>
Has more capability than
<code class="literal">
MODIFY
</code>
or
<code class="literal">
RENAME COLUMN
</code>
, but at the expense of
convenience for some operations.
<code class="literal">
CHANGE
</code>
requires naming the column twice if not renaming it, and
requires respecifying the column definition if only
renaming it.
</p>
</li>
<li class="listitem">
<p>
With
<code class="literal">
FIRST
</code>
or
<code class="literal">
AFTER
</code>
,
can reorder columns.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
MODIFY
</code>
:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Can change a column definition but not its name.
</p>
</li>
<li class="listitem">
<p>
More convenient than
<code class="literal">
CHANGE
</code>
to change a
column definition without renaming it.
</p>
</li>
<li class="listitem">
<p>
With
<code class="literal">
FIRST
</code>
or
<code class="literal">
AFTER
</code>
,
can reorder columns.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
RENAME COLUMN
</code>
:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem">
<p>
Can change a column name but not its definition.
</p>
</li>
<li class="listitem">
<p>
More convenient than
<code class="literal">
CHANGE
</code>
to rename a
column without changing its definition.
</p>
</li>
</ul>
</div>
</li>
<li class="listitem">
<p>
<code class="literal">
ALTER
</code>
: Used only to change a column default
value.
</p>
</li>
</ul>
</div>
<a class="indexterm" name="idm46045189098400">
</a>
<a class="indexterm" name="idm46045189097328">
</a>
<p>
<code class="literal">
CHANGE
</code>
is a MySQL extension to standard SQL.
<code class="literal">
MODIFY
</code>
and
<code class="literal">
RENAME COLUMN
</code>
are
MySQL extensions for Oracle compatibility.
</p>
<p>
To alter a column to change both its name and definition, use
<code class="literal">
CHANGE
</code>
, specifying the old and new names and
the new definition. For example, to rename an
<code class="literal">
INT NOT
NULL
</code>
column from
<code class="literal">
a
</code>
to
<code class="literal">
b
</code>
and change its definition to use the
<code class="literal">
BIGINT
</code>
data type while retaining the
<code class="literal">
NOT NULL
</code>
attribute, do this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa62279787"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">CHANGE</span> a b <span class="token datatype">BIGINT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To change a column definition but not its name, use
<code class="literal">
CHANGE
</code>
or
<code class="literal">
MODIFY
</code>
. With
<code class="literal">
CHANGE
</code>
, the syntax requires two column names,
so you must specify the same name twice to leave the name
unchanged. For example, to change the definition of column
<code class="literal">
b
</code>
, do this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa15469092"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">CHANGE</span> b b <span class="token datatype">INT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
<code class="literal">
MODIFY
</code>
is more convenient to change the
definition without changing the name because it requires the
column name only once:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa33906722"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">MODIFY</span> b <span class="token datatype">INT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
To change a column name but not its definition, use
<code class="literal">
CHANGE
</code>
or
<code class="literal">
RENAME COLUMN
</code>
.
With
<code class="literal">
CHANGE
</code>
, the syntax requires a column
definition, so to leave the definition unchanged, you must
respecify the definition the column currently has. For example, to
rename an
<code class="literal">
INT NOT NULL
</code>
column from
<code class="literal">
b
</code>
to
<code class="literal">
a
</code>
, do this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa91860529"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">CHANGE</span> b a <span class="token datatype">INT</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
<code class="literal">
RENAME COLUMN
</code>
is more convenient to change the
name without changing the definition because it requires only the
old and new names:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa3473577"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">RENAME</span> <span class="token keyword">COLUMN</span> b <span class="token keyword">TO</span> a<span class="token punctuation">;</span></code></pre>
</div>
<p>
In general, you cannot rename a column to a name that already
exists in the table. However, this is sometimes not the case, such
as when you swap names or move them through a cycle. If a table
has columns named
<code class="literal">
a
</code>
,
<code class="literal">
b
</code>
, and
<code class="literal">
c
</code>
, these are valid operations:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa58698386"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token comment" spellcheck="true">-- swap a and b</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">RENAME</span> <span class="token keyword">COLUMN</span> a <span class="token keyword">TO</span> b<span class="token punctuation">,</span>
<span class="token keyword">RENAME</span> <span class="token keyword">COLUMN</span> b <span class="token keyword">TO</span> a<span class="token punctuation">;</span>
<span class="token comment" spellcheck="true">-- "rotate" a, b, c through a cycle</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">RENAME</span> <span class="token keyword">COLUMN</span> a <span class="token keyword">TO</span> b<span class="token punctuation">,</span>
<span class="token keyword">RENAME</span> <span class="token keyword">COLUMN</span> b <span class="token keyword">TO</span> c<span class="token punctuation">,</span>
<span class="token keyword">RENAME</span> <span class="token keyword">COLUMN</span> c <span class="token keyword">TO</span> a<span class="token punctuation">;</span></code></pre>
</div>
<p>
For column definition changes using
<code class="literal">
CHANGE
</code>
or
<code class="literal">
MODIFY
</code>
, the definition must include the data
type and all attributes that should apply to the new column, other
than index attributes such as
<code class="literal">
PRIMARY KEY
</code>
or
<code class="literal">
UNIQUE
</code>
. Attributes present in the original
definition but not specified for the new definition are not
carried forward. Suppose that a column
<code class="literal">
col1
</code>
is
defined as
<code class="literal">
INT UNSIGNED DEFAULT 1 COMMENT 'my
column'
</code>
and you modify the column as follows, intending
to change only
<code class="literal">
INT
</code>
to
<code class="literal">
BIGINT
</code>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa36479411"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">MODIFY</span> col1 <span class="token datatype">BIGINT</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
That statement changes the data type from
<code class="literal">
INT
</code>
to
<code class="literal">
BIGINT
</code>
, but it also drops the
<code class="literal">
UNSIGNED
</code>
,
<code class="literal">
DEFAULT
</code>
, and
<code class="literal">
COMMENT
</code>
attributes. To retain them, the
statement must include them explicitly:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa94917873"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">MODIFY</span> col1 <span class="token datatype">BIGINT</span> <span class="token keyword">UNSIGNED</span> <span class="token keyword">DEFAULT</span> <span class="token number">1</span> <span class="token keyword">COMMENT</span> <span class="token string">'my column'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
For data type changes using
<code class="literal">
CHANGE
</code>
or
<code class="literal">
MODIFY
</code>
, MySQL tries to convert existing column
values to the new type as well as possible.
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
This conversion may result in alteration of data. For example,
if you shorten a string column, values may be truncated. To
prevent the operation from succeeding if conversions to the new
data type would result in loss of data, enable strict SQL mode
before using
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
(see
<a class="xref" href="sql-mode.html" title="7.1.11 Server SQL Modes">
Section 7.1.11, “Server SQL Modes”
</a>
).
</p>
</div>
<p>
If you use
<code class="literal">
CHANGE
</code>
or
<code class="literal">
MODIFY
</code>
to shorten a column for which an index exists on the column, and
the resulting column length is less than the index length, MySQL
shortens the index automatically.
</p>
<p>
For columns renamed by
<code class="literal">
CHANGE
</code>
or
<code class="literal">
RENAME COLUMN
</code>
, MySQL automatically renames
these references to the renamed column:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Indexes that refer to the old column, including invisible
indexes and disabled
<code class="literal">
MyISAM
</code>
indexes.
</p>
</li>
<li class="listitem">
<p>
Foreign keys that refer to the old column.
</p>
</li>
</ul>
</div>
<p>
For columns renamed by
<code class="literal">
CHANGE
</code>
or
<code class="literal">
RENAME COLUMN
</code>
, MySQL does not automatically
rename these references to the renamed column:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Generated column and partition expressions that refer to the
renamed column. You must use
<code class="literal">
CHANGE
</code>
to
redefine such expressions in the same
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
statement as the
one that renames the column.
</p>
</li>
<li class="listitem">
<p>
Views and stored programs that refer to the renamed column.
You must manually alter the definition of these objects to
refer to the new column name.
</p>
</li>
</ul>
</div>
<p>
To reorder columns within a table, use
<code class="literal">
FIRST
</code>
and
<code class="literal">
AFTER
</code>
in
<code class="literal">
CHANGE
</code>
or
<code class="literal">
MODIFY
</code>
operations.
</p>
<a class="indexterm" name="idm46045189035088">
</a>
<p>
<code class="literal">
ALTER ... SET DEFAULT
</code>
or
<code class="literal">
ALTER ...
DROP DEFAULT
</code>
specify a new default value for a column or
remove the old default value, respectively. If the old default is
removed and the column can be
<code class="literal">
NULL
</code>
, the new
default is
<code class="literal">
NULL
</code>
. If the column cannot be
<code class="literal">
NULL
</code>
, MySQL assigns a default value as
described in
<a class="xref" href="data-type-defaults.html" title="13.6 Data Type Default Values">
Section 13.6, “Data Type Default Values”
</a>
.
</p>
<p>
<code class="literal">
ALTER ... SET VISIBLE
</code>
and
<code class="literal">
ALTER ...
SET INVISIBLE
</code>
enable column visibility to be changed.
See
<a class="xref" href="invisible-columns.html" title="15.1.20.10 Invisible Columns">
Section 15.1.20.10, “Invisible Columns”
</a>
.
</p>
<h4>
<a name="alter-table-index">
</a>
Primary Keys and Indexes
</h4>
<a class="indexterm" name="idm46045189025408">
</a>
<a class="indexterm" name="idm46045189024368">
</a>
<a class="indexterm" name="idm46045189022880">
</a>
<p>
<code class="literal">
DROP PRIMARY KEY
</code>
drops the
<a class="link" href="glossary.html#glos_primary_key" title="primary key">
primary key
</a>
. If there is
no primary key, an error occurs. For information about the
performance characteristics of primary keys, especially for
<code class="literal">
InnoDB
</code>
tables, see
<a class="xref" href="primary-key-optimization.html" title="10.3.2 Primary Key Optimization">
Section 10.3.2, “Primary Key Optimization”
</a>
.
</p>
<p>
If the
<a class="link" href="server-system-variables.html#sysvar_sql_require_primary_key">
<code class="literal">
sql_require_primary_key
</code>
</a>
system variable is enabled, attempting to drop a primary key
produces an error.
</p>
<a class="indexterm" name="idm46045189015968">
</a>
<a class="indexterm" name="idm46045189014896">
</a>
<p>
If you add a
<code class="literal">
UNIQUE INDEX
</code>
or
<code class="literal">
PRIMARY
KEY
</code>
to a table, MySQL stores it before any nonunique
index to permit detection of duplicate keys as early as possible.
</p>
<a class="indexterm" name="idm46045189011856">
</a>
<a class="indexterm" name="idm46045189010784">
</a>
<a class="indexterm" name="idm46045189009296">
</a>
<p>
<a class="link" href="drop-index.html" title="15.1.27 DROP INDEX Statement">
<code class="literal">
DROP INDEX
</code>
</a>
removes an index. This
is a MySQL extension to standard SQL. See
<a class="xref" href="drop-index.html" title="15.1.27 DROP INDEX Statement">
Section 15.1.27, “DROP INDEX Statement”
</a>
. To determine index names, use
<code class="literal">
SHOW INDEX FROM
<em class="replaceable">
<code>
tbl_name
</code>
</em>
</code>
.
</p>
<p>
Some storage engines permit you to specify an index type when
creating an index. The syntax for the
<em class="replaceable">
<code>
index_type
</code>
</em>
specifier is
<code class="literal">
USING
<em class="replaceable">
<code>
type_name
</code>
</em>
</code>
. For details about
<code class="literal">
USING
</code>
, see
<a class="xref" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
Section 15.1.15, “CREATE INDEX Statement”
</a>
. The
preferred position is after the column list. Expect support for
use of the option before the column list to be removed in a future
MySQL release.
</p>
<p>
<em class="replaceable">
<code>
index_option
</code>
</em>
values specify additional
options for an index.
<code class="literal">
USING
</code>
is one such option.
For details about permissible
<em class="replaceable">
<code>
index_option
</code>
</em>
values, see
<a class="xref" href="create-index.html" title="15.1.15 CREATE INDEX Statement">
Section 15.1.15, “CREATE INDEX Statement”
</a>
.
</p>
<p>
<code class="literal">
RENAME INDEX
<em class="replaceable">
<code>
old_index_name
</code>
</em>
TO
<em class="replaceable">
<code>
new_index_name
</code>
</em>
</code>
renames an
index. This is a MySQL extension to standard SQL. The content of
the table remains unchanged.
<em class="replaceable">
<code>
old_index_name
</code>
</em>
must be the name of an
existing index in the table that is not dropped by the same
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
statement.
<em class="replaceable">
<code>
new_index_name
</code>
</em>
is the new index name,
which cannot duplicate the name of an index in the resulting table
after changes have been applied. Neither index name can be
<code class="literal">
PRIMARY
</code>
.
</p>
<a class="indexterm" name="idm46045188993152">
</a>
<a class="indexterm" name="idm46045188992080">
</a>
<a class="indexterm" name="idm46045188990592">
</a>
<p>
If you use
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
on a
<code class="literal">
MyISAM
</code>
table, all nonunique indexes are created
in a separate batch (as for
<a class="link" href="repair-table.html" title="15.7.3.5 REPAIR TABLE Statement">
<code class="literal">
REPAIR
TABLE
</code>
</a>
). This should make
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE
</code>
</a>
much faster when you have many indexes.
</p>
<p>
For
<code class="literal">
MyISAM
</code>
tables, key updating can be
controlled explicitly. Use
<code class="literal">
ALTER TABLE ... DISABLE
KEYS
</code>
to tell MySQL to stop updating nonunique indexes.
Then use
<code class="literal">
ALTER TABLE ... ENABLE KEYS
</code>
to
re-create missing indexes.
<code class="literal">
MyISAM
</code>
does this
with a special algorithm that is much faster than inserting keys
one by one, so disabling keys before performing bulk insert
operations should give a considerable speedup. Using
<code class="literal">
ALTER TABLE ... DISABLE KEYS
</code>
requires the
<a class="link" href="privileges-provided.html#priv_index">
<code class="literal">
INDEX
</code>
</a>
privilege in addition to the
privileges mentioned earlier.
</p>
<p>
While the nonunique indexes are disabled, they are ignored for
statements such as
<a class="link" href="select.html" title="15.2.13 SELECT Statement">
<code class="literal">
SELECT
</code>
</a>
and
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
that otherwise would use
them.
</p>
<p>
After an
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
statement, it
may be necessary to run
<a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
<code class="literal">
ANALYZE
TABLE
</code>
</a>
to update index cardinality information. See
<a class="xref" href="show-index.html" title="15.7.7.23 SHOW INDEX Statement">
Section 15.7.7.23, “SHOW INDEX Statement”
</a>
.
</p>
<a class="indexterm" name="idm46045188971920">
</a>
<p>
The
<code class="literal">
ALTER INDEX
</code>
operation permits an index to
be made visible or invisible. An invisible index is not used by
the optimizer. Modification of index visibility applies to indexes
other than primary keys (either explicit or implicit), and cannot
be performed using
<code class="literal">
ALGORITHM=INSTANT
</code>
. This
feature is storage engine neutral (supported for any engine). For
more information, see
<a class="xref" href="invisible-indexes.html" title="10.3.12 Invisible Indexes">
Section 10.3.12, “Invisible Indexes”
</a>
.
</p>
<h4>
<a name="alter-table-foreign-key">
</a>
Foreign Keys and Other Constraints
</h4>
<a class="indexterm" name="idm46045188966784">
</a>
<a class="indexterm" name="idm46045188965744">
</a>
<p>
The
<code class="literal">
FOREIGN KEY
</code>
and
<code class="literal">
REFERENCES
</code>
clauses are supported by the
<code class="literal">
InnoDB
</code>
and
<code class="literal">
NDB
</code>
storage
engines, which implement
<code class="literal">
ADD [CONSTRAINT
[
<em class="replaceable">
<code>
symbol
</code>
</em>
]] FOREIGN KEY
[
<em class="replaceable">
<code>
index_name
</code>
</em>
] (...) REFERENCES ...
(...)
</code>
. See
<a class="xref" href="create-table-foreign-keys.html" title="15.1.20.5 FOREIGN KEY Constraints">
Section 15.1.20.5, “FOREIGN KEY Constraints”
</a>
.
For other storage engines, the clauses are parsed but ignored.
</p>
<p>
For
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
, unlike
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
,
<code class="literal">
ADD FOREIGN
KEY
</code>
ignores
<em class="replaceable">
<code>
index_name
</code>
</em>
if
given and uses an automatically generated foreign key name. As a
workaround, include the
<code class="literal">
CONSTRAINT
</code>
clause to
specify the foreign key name:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa68560052"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ADD</span> <span class="token keyword">CONSTRAINT</span> <span class="token keyword"><em class="replaceable">name</em></span> <span class="token keyword">FOREIGN</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre>
</div>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
MySQL silently ignores inline
<code class="literal">
REFERENCES
</code>
specifications, where the references are defined as part of the
column specification. MySQL accepts only
<code class="literal">
REFERENCES
</code>
clauses defined as part of a
separate
<code class="literal">
FOREIGN KEY
</code>
specification.
</p>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Partitioned
<code class="literal">
InnoDB
</code>
tables do not support
foreign keys. This restriction does not apply to
<code class="literal">
NDB
</code>
tables, including those explicitly
partitioned by
<code class="literal">
[LINEAR] KEY
</code>
. For more
information, see
<a class="xref" href="partitioning-limitations-storage-engines.html" title="26.6.2 Partitioning Limitations Relating to Storage Engines">
Section 26.6.2, “Partitioning Limitations Relating to Storage Engines”
</a>
.
</p>
</div>
<a class="indexterm" name="idm46045188945520">
</a>
<a class="indexterm" name="idm46045188944448">
</a>
<a class="indexterm" name="idm46045188942960">
</a>
<p>
MySQL Server and NDB Cluster both support the use of
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
to drop foreign keys:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa75617452"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em> <span class="token keyword">DROP</span> <span class="token keyword">FOREIGN</span> <span class="token keyword">KEY</span> <em class="replaceable">fk_symbol</em><span class="token punctuation">;</span></code></pre>
</div>
<p>
Adding and dropping a foreign key in the same
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
statement is supported
for
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE ...
ALGORITHM=INPLACE
</code>
</a>
but not for
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE ...
ALGORITHM=COPY
</code>
</a>
.
</p>
<p>
The server prohibits changes to foreign key columns that have the
potential to cause loss of referential integrity. A workaround is
to use
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
... DROP FOREIGN KEY
</code>
</a>
before changing the column
definition and
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER
TABLE ... ADD FOREIGN KEY
</code>
</a>
afterward. Examples of
prohibited changes include:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Changes to the data type of foreign key columns that may be
unsafe. For example, changing
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR(20)
</code>
</a>
to
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR(30)
</code>
</a>
is permitted, but
changing it to
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR(1024)
</code>
</a>
is
not because that alters the number of length bytes required to
store individual values.
</p>
</li>
<li class="listitem">
<p>
Changing a
<code class="literal">
NULL
</code>
column to
<code class="literal">
NOT
NULL
</code>
in non-strict mode is prohibited to prevent
converting
<code class="literal">
NULL
</code>
values to default
non-
<code class="literal">
NULL
</code>
values, for which there are no
corresponding values in the referenced table. The operation is
permitted in strict mode, but an error is returned if any such
conversion is required.
</p>
</li>
</ul>
</div>
<p>
<code class="literal">
ALTER TABLE
<em class="replaceable">
<code>
tbl_name
</code>
</em>
RENAME
<em class="replaceable">
<code>
new_tbl_name
</code>
</em>
</code>
changes
internally generated foreign key constraint names and user-defined
foreign key constraint names that begin with the string
<span class="quote">
“
<span class="quote">
<em class="replaceable">
<code>
tbl_name
</code>
</em>
_ibfk_
</span>
”
</span>
to
reflect the new table name.
<code class="literal">
InnoDB
</code>
interprets
foreign key constraint names that begin with the string
<span class="quote">
“
<span class="quote">
<em class="replaceable">
<code>
tbl_name
</code>
</em>
_ibfk_
</span>
”
</span>
as
internally generated names.
</p>
<a class="indexterm" name="idm46045188917328">
</a>
<p>
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
permits
<code class="literal">
CHECK
</code>
constraints for existing tables to be
added, dropped, or altered:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Add a new
<code class="literal">
CHECK
</code>
constraint:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa68801855"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em>
<span class="token keyword">ADD</span> <span class="token punctuation">[</span><span class="token keyword">CONSTRAINT</span> <span class="token punctuation">[</span><em class="replaceable">symbol</em><span class="token punctuation">]</span><span class="token punctuation">]</span> <span class="token keyword">CHECK</span> <span class="token punctuation">(</span><em class="replaceable">expr</em><span class="token punctuation">)</span> <span class="token punctuation">[</span><span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> <span class="token keyword">ENFORCED</span><span class="token punctuation">]</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The meaning of constraint syntax elements is the same as for
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
. See
<a class="xref" href="create-table-check-constraints.html" title="15.1.20.6 CHECK Constraints">
Section 15.1.20.6, “CHECK Constraints”
</a>
.
</p>
</li>
<li class="listitem">
<p>
Drop an existing
<code class="literal">
CHECK
</code>
constraint named
<em class="replaceable">
<code>
symbol
</code>
</em>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa63969837"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em>
<span class="token keyword">DROP</span> <span class="token keyword">CHECK</span> <em class="replaceable">symbol</em><span class="token punctuation">;</span></code></pre>
</div>
</li>
<li class="listitem">
<p>
Alter whether an existing
<code class="literal">
CHECK
</code>
constraint
named
<em class="replaceable">
<code>
symbol
</code>
</em>
is enforced:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa76747192"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em>
<span class="token keyword">ALTER</span> <span class="token keyword">CHECK</span> <em class="replaceable">symbol</em> <span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> <span class="token keyword">ENFORCED</span><span class="token punctuation">;</span></code></pre>
</div>
</li>
</ul>
</div>
<p>
The
<code class="literal">
DROP CHECK
</code>
and
<code class="literal">
ALTER
CHECK
</code>
clauses are MySQL extensions to standard SQL.
</p>
<p>
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
permits more general
(and SQL standard) syntax for dropping and altering existing
constraints of any type, where the constraint type is determined
from the constraint name:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Drop an existing constraint named
<em class="replaceable">
<code>
symbol
</code>
</em>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa10600870"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em>
<span class="token keyword">DROP</span> <span class="token keyword">CONSTRAINT</span> <em class="replaceable">symbol</em><span class="token punctuation">;</span></code></pre>
</div>
<p>
If the
<a class="link" href="server-system-variables.html#sysvar_sql_require_primary_key">
<code class="literal">
sql_require_primary_key
</code>
</a>
system variable is enabled, attempting to drop a primary key
produces an error.
</p>
</li>
<li class="listitem">
<p>
Alter whether an existing constraint named
<em class="replaceable">
<code>
symbol
</code>
</em>
is enforced:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa36041624"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em>
<span class="token keyword">ALTER</span> <span class="token keyword">CONSTRAINT</span> <em class="replaceable">symbol</em> <span class="token punctuation">[</span><span class="token operator">NOT</span><span class="token punctuation">]</span> <span class="token keyword">ENFORCED</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
Only
<code class="literal">
CHECK
</code>
constraints can be altered to be
unenforced. All other constraint types are always enforced.
</p>
</li>
</ul>
</div>
<p>
The SQL standard specifies that all types of constraints (primary
key, unique index, foreign key, check) belong to the same
namespace. In MySQL, each constraint type has its own namespace
per schema. Consequently, names for each type of constraint must
be unique per schema, but constraints of different types can have
the same name. When multiple constraints have the same name,
<code class="literal">
DROP CONSTRAINT
</code>
and
<code class="literal">
ADD
CONSTRAINT
</code>
are ambiguous and an error occurs. In such
cases, constraint-specific syntax must be used to modify the
constraint. For example, use
<code class="literal">
DROP PRIMARY KEY
</code>
or DROP FOREIGN KEY to drop a primary key or foreign key.
</p>
<p>
If a table alteration causes a violation of an enforced
<code class="literal">
CHECK
</code>
constraint, an error occurs and the table
is not modified. Examples of operations for which an error occurs:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Attempts to add the
<code class="literal">
AUTO_INCREMENT
</code>
attribute to a column that is used in a
<code class="literal">
CHECK
</code>
constraint.
</p>
</li>
<li class="listitem">
<p>
Attempts to add an enforced
<code class="literal">
CHECK
</code>
constraint or enforce a nonenforced
<code class="literal">
CHECK
</code>
constraint for which existing rows violate the constraint
condition.
</p>
</li>
<li class="listitem">
<p>
Attempts to modify, rename, or drop a column that is used in a
<code class="literal">
CHECK
</code>
constraint, unless that constraint is
also dropped in the same statement. Exception: If a
<code class="literal">
CHECK
</code>
constraint refers only to a single
column, dropping the column automatically drops the
constraint.
</p>
</li>
</ul>
</div>
<p>
<code class="literal">
ALTER TABLE
<em class="replaceable">
<code>
tbl_name
</code>
</em>
RENAME
<em class="replaceable">
<code>
new_tbl_name
</code>
</em>
</code>
changes
internally generated and user-defined
<code class="literal">
CHECK
</code>
constraint names that begin with the string
<span class="quote">
“
<span class="quote">
<em class="replaceable">
<code>
tbl_name
</code>
</em>
_chk_
</span>
”
</span>
to reflect
the new table name. MySQL interprets
<code class="literal">
CHECK
</code>
constraint names that begin with the string
<span class="quote">
“
<span class="quote">
<em class="replaceable">
<code>
tbl_name
</code>
</em>
_chk_
</span>
”
</span>
as
internally generated names.
</p>
<h4>
<a name="alter-table-character-set">
</a>
Changing the Character Set
</h4>
<p>
<a class="indexterm" name="idm46045188867552">
</a>
To change the table default character set and all character
columns (
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
,
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
) to a new character set, use a
statement like this:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa32961287"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em> CONVERT <span class="token keyword">TO</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <em class="replaceable">charset_name</em><span class="token punctuation">;</span></code></pre>
</div>
<p>
The statement also changes the collation of all character columns.
If you specify no
<code class="literal">
COLLATE
</code>
clause to indicate
which collation to use, the statement uses default collation for
the character set. If this collation is inappropriate for the
intended table use (for example, if it would change from a
case-sensitive collation to a case-insensitive collation), specify
a collation explicitly.
</p>
<p>
For a column that has a data type of
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
or one of the
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
types,
<code class="literal">
CONVERT TO
CHARACTER SET
</code>
changes the data type as necessary to
ensure that the new column is long enough to store as many
characters as the original column. For example, a
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
column has two length bytes,
which store the byte-length of values in the column, up to a
maximum of 65,535. For a
<code class="literal">
latin1
</code>
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
column, each character
requires a single byte, so the column can store up to 65,535
characters. If the column is converted to
<code class="literal">
utf8mb4
</code>
, each character might require up to 4
bytes, for a maximum possible length of 4 × 65,535 = 262,140
bytes. That length does not fit in a
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
column's length bytes, so
MySQL converts the data type to
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
MEDIUMTEXT
</code>
</a>
, which is the smallest
string type for which the length bytes can record a value of
262,140. Similarly, a
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
column might be converted to
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
MEDIUMTEXT
</code>
</a>
.
</p>
<p>
To avoid data type changes of the type just described, do not use
<code class="literal">
CONVERT TO CHARACTER SET
</code>
. Instead, use
<code class="literal">
MODIFY
</code>
to change individual columns. For
example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34821741"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t <span class="token keyword">MODIFY</span> latin1_text_col <span class="token datatype">TEXT</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> utf8mb4<span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t <span class="token keyword">MODIFY</span> latin1_varchar_col <span class="token datatype">VARCHAR</span><span class="token punctuation">(</span><em class="replaceable">M</em><span class="token punctuation">)</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> utf8mb4<span class="token punctuation">;</span></code></pre>
</div>
<p>
If you specify
<code class="literal">
CONVERT TO CHARACTER SET binary
</code>
,
the
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
CHAR
</code>
</a>
,
<a class="link" href="char.html" title="13.3.2 The CHAR and VARCHAR Types">
<code class="literal">
VARCHAR
</code>
</a>
, and
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
TEXT
</code>
</a>
columns are converted to their
corresponding binary string types
(
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
BINARY
</code>
</a>
,
<a class="link" href="binary-varbinary.html" title="13.3.3 The BINARY and VARBINARY Types">
<code class="literal">
VARBINARY
</code>
</a>
,
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
). This means that the columns
no longer have a character set and a subsequent
<code class="literal">
CONVERT
TO
</code>
operation does not apply to them.
</p>
<p>
If
<em class="replaceable">
<code>
charset_name
</code>
</em>
is
<code class="literal">
DEFAULT
</code>
in a
<code class="literal">
CONVERT TO CHARACTER
SET
</code>
operation, the character set named by the
<a class="link" href="server-system-variables.html#sysvar_character_set_database">
<code class="literal">
character_set_database
</code>
</a>
system
variable is used.
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
The
<code class="literal">
CONVERT TO
</code>
operation converts column
values between the original and named character sets. This is
<span class="emphasis">
<em>
not
</em>
</span>
what you want if you have a column in
one character set (like
<code class="literal">
latin1
</code>
) but the
stored values actually use some other, incompatible character
set (like
<code class="literal">
utf8mb4
</code>
). In this case, you have to
do the following for each such column:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa51832325"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">CHANGE</span> c1 c1 <span class="token datatype">BLOB</span><span class="token punctuation">;</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> t1 <span class="token keyword">CHANGE</span> c1 c1 <span class="token datatype">TEXT</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> utf8mb4<span class="token punctuation">;</span></code></pre>
</div>
<p>
The reason this works is that there is no conversion when you
convert to or from
<a class="link" href="blob.html" title="13.3.4 The BLOB and TEXT Types">
<code class="literal">
BLOB
</code>
</a>
columns.
</p>
</div>
<p>
To change only the
<span class="emphasis">
<em>
default
</em>
</span>
character set for
a table, use this statement:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa17876601"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <em class="replaceable">tbl_name</em> <span class="token keyword">DEFAULT</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> <em class="replaceable">charset_name</em><span class="token punctuation">;</span></code></pre>
</div>
<p>
The word
<code class="literal">
DEFAULT
</code>
is optional. The default
character set is the character set that is used if you do not
specify the character set for columns that you add to a table
later (for example, with
<code class="literal">
ALTER TABLE ... ADD
column
</code>
).
</p>
<p>
When the
<a class="link" href="server-system-variables.html#sysvar_foreign_key_checks">
<code class="literal">
foreign_key_checks
</code>
</a>
system variable is enabled, which is the default setting,
character set conversion is not permitted on tables that include a
character string column used in a foreign key constraint. The
workaround is to disable
<a class="link" href="server-system-variables.html#sysvar_foreign_key_checks">
<code class="literal">
foreign_key_checks
</code>
</a>
before
performing the character set conversion. You must perform the
conversion on both tables involved in the foreign key constraint
before re-enabling
<a class="link" href="server-system-variables.html#sysvar_foreign_key_checks">
<code class="literal">
foreign_key_checks
</code>
</a>
. If you
re-enable
<a class="link" href="server-system-variables.html#sysvar_foreign_key_checks">
<code class="literal">
foreign_key_checks
</code>
</a>
after converting only one of the tables, an
<code class="literal">
ON DELETE
CASCADE
</code>
or
<code class="literal">
ON UPDATE CASCADE
</code>
operation could corrupt data in the referencing table due to
implicit conversion that occurs during these operations (Bug
#45290, Bug #74816).
</p>
<h4>
<a name="alter-table-import">
</a>
Importing InnoDB Tables
</h4>
<a class="indexterm" name="idm46045188809568">
</a>
<a class="indexterm" name="idm46045188808496">
</a>
<p>
An
<code class="literal">
InnoDB
</code>
table created in its own
<a class="link" href="glossary.html#glos_file_per_table" title="file-per-table">
file-per-table
</a>
tablespace can be imported from a backup or from another MySQL
server instance using
<code class="literal">
DISCARD TABLEPACE
</code>
and
<code class="literal">
IMPORT TABLESPACE
</code>
clauses. See
<a class="xref" href="innodb-table-import.html" title="17.6.1.3 Importing InnoDB Tables">
Section 17.6.1.3, “Importing InnoDB Tables”
</a>
.
</p>
<h4>
<a name="alter-table-row-order">
</a>
Row Order for MyISAM Tables
</h4>
<a class="indexterm" name="idm46045188801936">
</a>
<p>
<code class="literal">
ORDER BY
</code>
enables you to create the new table
with the rows in a specific order. This option is useful primarily
when you know that you query the rows in a certain order most of
the time. By using this option after major changes to the table,
you might be able to get higher performance. In some cases, it
might make sorting easier for MySQL if the table is in order by
the column that you want to order it by later.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
The table does not remain in the specified order after inserts
and deletes.
</p>
</div>
<p>
<code class="literal">
ORDER BY
</code>
syntax permits one or more column
names to be specified for sorting, each of which optionally can be
followed by
<code class="literal">
ASC
</code>
or
<code class="literal">
DESC
</code>
to
indicate ascending or descending sort order, respectively. The
default is ascending order. Only column names are permitted as
sort criteria; arbitrary expressions are not permitted. This
clause should be given last after any other clauses.
</p>
<p>
<code class="literal">
ORDER BY
</code>
does not make sense for
<code class="literal">
InnoDB
</code>
tables because
<code class="literal">
InnoDB
</code>
always orders table rows according to the
<a class="link" href="glossary.html#glos_clustered_index" title="clustered index">
clustered index
</a>
.
</p>
<p>
When used on a partitioned table,
<code class="literal">
ALTER TABLE ... ORDER
BY
</code>
orders rows within each partition only.
</p>
<h4>
<a name="alter-table-partition-options">
</a>
Partitioning Options
</h4>
<p>
<em class="replaceable">
<code>
partition_options
</code>
</em>
signifies options
that can be used with partitioned tables for repartitioning, to
add, drop, discard, import, merge, and split partitions, and to
perform partitioning maintenance.
</p>
<p>
It is possible for an
<a class="link" href="alter-table.html" title="15.1.9 ALTER TABLE Statement">
<code class="literal">
ALTER TABLE
</code>
</a>
statement to contain a
<code class="literal">
PARTITION BY
</code>
or
<code class="literal">
REMOVE PARTITIONING
</code>
clause in an addition to
other alter specifications, but the
<code class="literal">
PARTITION
BY
</code>
or
<code class="literal">
REMOVE PARTITIONING
</code>
clause must
be specified last after any other specifications. The
<code class="literal">
ADD
PARTITION
</code>
,
<code class="literal">
DROP PARTITION
</code>
,
<code class="literal">
DISCARD PARTITION
</code>
,
<code class="literal">
IMPORT
PARTITION
</code>
,
<code class="literal">
COALESCE PARTITION
</code>
,
<code class="literal">
REORGANIZE PARTITION
</code>
,
<code class="literal">
EXCHANGE
PARTITION
</code>
,
<code class="literal">
ANALYZE PARTITION
</code>
,
<code class="literal">
CHECK PARTITION
</code>
, and
<code class="literal">
REPAIR
PARTITION
</code>
options cannot be combined with other alter
specifications in a single
<code class="literal">
ALTER TABLE
</code>
, since
the options just listed act on individual partitions.
</p>
<p>
For more information about partition options, see
<a class="xref" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
Section 15.1.20, “CREATE TABLE Statement”
</a>
, and
<a class="xref" href="alter-table-partition-operations.html" title="15.1.9.1 ALTER TABLE Partition Operations">
Section 15.1.9.1, “ALTER TABLE Partition Operations”
</a>
. For
information about and examples of
<code class="literal">
ALTER TABLE ...
EXCHANGE PARTITION
</code>
statements, see
<a class="xref" href="partitioning-management-exchange.html" title="26.3.3 Exchanging Partitions and Subpartitions with Tables">
Section 26.3.3, “Exchanging Partitions and Subpartitions with Tables”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/rename-user.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="rename-user">
</a>
15.7.1.7 RENAME USER Statement
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045173199328">
</a>
<a class="indexterm" name="idm46045173198256">
</a>
<a class="indexterm" name="idm46045173196768">
</a>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa89561826"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">RENAME</span> <span class="token keyword">USER</span> <em class="replaceable">old_user</em> <span class="token keyword">TO</span> <em class="replaceable">new_user</em>
<span class="token punctuation">[</span><span class="token punctuation">,</span> <em class="replaceable">old_user</em> <span class="token keyword">TO</span> <em class="replaceable">new_user</em><span class="token punctuation">]</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre>
</div>
<p>
The
<a class="link" href="rename-user.html" title="15.7.1.7 RENAME USER Statement">
<code class="literal">
RENAME USER
</code>
</a>
statement renames
existing MySQL accounts. An error occurs for old accounts that
do not exist or new accounts that already exist.
</p>
<p>
To use
<a class="link" href="rename-user.html" title="15.7.1.7 RENAME USER Statement">
<code class="literal">
RENAME USER
</code>
</a>
, you must have
the global
<a class="link" href="privileges-provided.html#priv_create-user">
<code class="literal">
CREATE USER
</code>
</a>
privilege,
or the
<a class="link" href="privileges-provided.html#priv_update">
<code class="literal">
UPDATE
</code>
</a>
privilege for the
<code class="literal">
mysql
</code>
system schema. When the
<a class="link" href="server-system-variables.html#sysvar_read_only">
<code class="literal">
read_only
</code>
</a>
system variable is
enabled,
<a class="link" href="rename-user.html" title="15.7.1.7 RENAME USER Statement">
<code class="literal">
RENAME USER
</code>
</a>
additionally
requires the
<a class="link" href="privileges-provided.html#priv_connection-admin">
<code class="literal">
CONNECTION_ADMIN
</code>
</a>
privilege (or the deprecated
<a class="link" href="privileges-provided.html#priv_super">
<code class="literal">
SUPER
</code>
</a>
privilege).
</p>
<p>
<a class="link" href="rename-user.html" title="15.7.1.7 RENAME USER Statement">
<code class="literal">
RENAME USER
</code>
</a>
fails with an error
if any account to be renamed is named as the
<code class="literal">
DEFINER
</code>
attribute for any stored object.
(That is, the statement fails if renaming an account would cause
a stored object to become orphaned.) To perform the operation
anyway, you must have the
<a class="link" href="privileges-provided.html#priv_set-any-definer">
<code class="literal">
SET_ANY_DEFINER
</code>
</a>
or
<a class="link" href="privileges-provided.html#priv_allow-nonexistent-definer">
<code class="literal">
ALLOW_NONEXISTENT_DEFINER
</code>
</a>
privilege; in this case, the statement succeeds with a warning
rather than failing with an error. For additional information,
including how to identify which objects name a given account as
the
<code class="literal">
DEFINER
</code>
attribute, see
<a class="xref" href="stored-objects-security.html#stored-objects-security-orphan-objects" title="Orphan Stored Objects">
Orphan Stored Objects
</a>
.
</p>
<p>
Each account name uses the format described in
<a class="xref" href="account-names.html" title="8.2.4 Specifying Account Names">
Section 8.2.4, “Specifying Account Names”
</a>
. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa85920903"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">RENAME</span> <span class="token keyword">USER</span> <span class="token string">'jeffrey'</span>@<span class="token string">'localhost'</span> <span class="token keyword">TO</span> <span class="token string">'jeff'</span>@<span class="token string">'127.0.0.1'</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
The host name part of the account name, if omitted, defaults to
<code class="literal">
'%'
</code>
.
</p>
<p>
<a class="link" href="rename-user.html" title="15.7.1.7 RENAME USER Statement">
<code class="literal">
RENAME USER
</code>
</a>
causes the privileges
held by the old user to be those held by the new user. However,
<a class="link" href="rename-user.html" title="15.7.1.7 RENAME USER Statement">
<code class="literal">
RENAME USER
</code>
</a>
does not
automatically drop or invalidate databases or objects within
them that the old user created. This includes stored programs or
views for which the
<code class="literal">
DEFINER
</code>
attribute names
the old user. Attempts to access such objects may produce an
error if they execute in definer security context. (For
information about security context, see
<a class="xref" href="stored-objects-security.html" title="27.6 Stored Object Access Control">
Section 27.6, “Stored Object Access Control”
</a>
.)
</p>
<p>
The privilege changes take effect as indicated in
<a class="xref" href="privilege-changes.html" title="8.2.13 When Privilege Changes Take Effect">
Section 8.2.13, “When Privilege Changes Take Effect”
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/key-cache-restructuring.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="key-cache-restructuring">
</a>
10.10.2.6 Restructuring a Key Cache
</h4>
</div>
</div>
</div>
<p>
A key cache can be restructured at any time by updating its
parameter values. For example:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa6346368"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> cold_cache<span class="token punctuation">.</span>key_buffer_size<span class="token operator">=</span><span class="token number">4</span><span class="token operator">*</span><span class="token number">1024</span><span class="token operator">*</span><span class="token number">1024</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If you assign to either the
<a class="link" href="server-system-variables.html#sysvar_key_buffer_size">
<code class="literal">
key_buffer_size
</code>
</a>
or
<a class="link" href="server-system-variables.html#sysvar_key_cache_block_size">
<code class="literal">
key_cache_block_size
</code>
</a>
key
cache component a value that differs from the component's
current value, the server destroys the cache's old
structure and creates a new one based on the new values. If
the cache contains any dirty blocks, the server saves them to
disk before destroying and re-creating the cache.
Restructuring does not occur if you change other key cache
parameters.
</p>
<p>
When restructuring a key cache, the server first flushes the
contents of any dirty buffers to disk. After that, the cache
contents become unavailable. However, restructuring does not
block queries that need to use indexes assigned to the cache.
Instead, the server directly accesses the table indexes using
native file system caching. File system caching is not as
efficient as using a key cache, so although queries execute, a
slowdown can be anticipated. After the cache has been
restructured, it becomes available again for caching indexes
assigned to it, and the use of file system caching for the
indexes ceases.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-replication-starting.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="mysql-cluster-replication-starting">
</a>
25.7.6 Starting NDB Cluster Replication (Single Replication Channel)
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045086100992">
</a>
<p>
This section outlines the procedure for starting NDB Cluster
replication using a single replication channel.
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Start the MySQL replication source server by issuing this
command, where
<em class="replaceable">
<code>
id
</code>
</em>
is this
server's unique ID (see
<a class="xref" href="mysql-cluster-replication-general.html" title="25.7.2 General Requirements for NDB Cluster Replication">
Section 25.7.2, “General Requirements for NDB Cluster Replication”
</a>
):
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-terminal"><div class="docs-select-all right" id="sa33674089"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal"><span class="token prompt">shell<em class="replaceable">S</em>></span><span class="token command"> mysqld</span> <span class="token property">--ndbcluster</span> <span class="token constant">--server-id</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">id</em></span> \
<span class="token property">--log-bin</span> <span class="token property">--ndb-log-bin</span> &</code></pre>
</div>
<p>
This starts the server's
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
process with binary logging enabled using the proper logging
format. It is also necessary to enable logging of updates to
<code class="literal">
NDB
</code>
tables explicitly, using the
<a class="link" href="mysql-cluster-options-variables.html#sysvar_ndb_log_bin">
<code class="option">
--ndb-log-bin
</code>
</a>
option.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
You can also start the source with
<a class="link" href="replication-options-binary-log.html#sysvar_binlog_format">
<code class="option">
--binlog-format=MIXED
</code>
</a>
, in
which case row-based replication is used automatically when
replicating between clusters. Statement-based binary logging
is not supported for NDB Cluster Replication (see
<a class="xref" href="mysql-cluster-replication-general.html" title="25.7.2 General Requirements for NDB Cluster Replication">
Section 25.7.2, “General Requirements for NDB Cluster Replication”
</a>
).
</p>
</div>
</li>
<li class="listitem">
<p>
Start the MySQL replica server as shown here:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-terminal"><div class="docs-select-all right" id="sa81595080"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-terminal">shell<em class="replaceable">R</em>> mysqld <span class="token property">--ndbcluster</span> <span class="token constant">--server-id</span><span class="token attr-value"><span class="token punctuation">=</span><em class="replaceable">id</em></span> &</code></pre>
</div>
<p>
In the command just shown,
<em class="replaceable">
<code>
id
</code>
</em>
is
the replica server's unique ID. It is not necessary to
enable logging on the replica.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Unless you want replication to begin immediately, delay the
start of the replication threads until the appropriate
<a class="link" href="start-replica.html" title="15.4.2.4 START REPLICA Statement">
<code class="literal">
START REPLICA
</code>
</a>
statement has
been issued, as explained in Step 4 below. You can do this
by starting the replica with
<a class="link" href="replication-options-replica.html#option_mysqld_skip-replica-start">
<code class="option">
--skip-replica-start
</code>
</a>
.
</p>
</div>
</li>
<li class="listitem">
<p>
It is necessary to synchronize the replica server with the
source server's replication binary log. If binary logging
has not previously been running on the source, run the
following statement on the replica:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa34464179"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">mysql<em class="replaceable">R</em><span class="token operator">></span> <span class="token keyword">CHANGE</span> <span class="token keyword">REPLICATION</span> <span class="token keyword">SOURCE</span> <span class="token keyword">TO</span>
<span class="token prompt"> -></span> <span class="token keyword">SOURCE_LOG_FILE</span><span class="token operator">=</span><span class="token string">''</span><span class="token punctuation">,</span>
<span class="token prompt"> -></span> <span class="token keyword">SOURCE_LOG_POS</span><span class="token operator">=</span><span class="token number">4</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This instructs the replica to begin reading the source
server's binary log from the log's starting point.
Otherwise—that is, if you are loading data from the
source using a backup—see
<a class="xref" href="mysql-cluster-replication-failover.html" title="25.7.8 Implementing Failover with NDB Cluster Replication">
Section 25.7.8, “Implementing Failover with NDB Cluster Replication”
</a>
, for
information on how to obtain the correct values to use for
<code class="literal">
SOURCE_LOG_FILE
</code>
and
<code class="literal">
SOURCE_LOG_POS
</code>
in such cases.
</p>
</li>
<li class="listitem">
<p>
Finally, instruct the replica to begin applying replication by
issuing this command from the
<a class="link" href="mysql.html" title="6.5.1 mysql — The MySQL Command-Line Client">
<span class="command">
<strong>
mysql
</strong>
</span>
</a>
client
on the replica:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa39502227"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql">mysql<em class="replaceable">R</em><span class="token operator">></span> <span class="token keyword">START</span> <span class="token keyword">REPLICA</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
This also initiates the transmission of data and changes from
the source to the replica.
</p>
</li>
</ol>
</div>
<p>
It is also possible to use two replication channels, in a manner
similar to the procedure described in the next section; the
differences between this and using a single replication channel
are covered in
<a class="xref" href="mysql-cluster-replication-two-channels.html" title="25.7.7 Using Two Replication Channels for NDB Cluster Replication">
Section 25.7.7, “Using Two Replication Channels for NDB Cluster Replication”
</a>
.
</p>
<a class="indexterm" name="idm46045086065488">
</a>
<p>
It is also possible to improve cluster replication performance by
enabling
<span class="firstterm">
batched updates
</span>
.
This can be accomplished by setting the system variable
<a class="link" href="mysql-cluster-options-variables.html#sysvar_replica_allow_batching">
<code class="literal">
replica_allow_batching
</code>
</a>
on the
replicas'
<a class="link" href="mysqld.html" title="6.3.1 mysqld — The MySQL Server">
<span class="command">
<strong>
mysqld
</strong>
</span>
</a>
processes. Normally,
updates are applied as soon as they are received. However, the use
of batching causes updates to be applied in batches of 32 KB each;
this can result in higher throughput and less CPU usage,
particularly where individual updates are relatively small.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Batching works on a per-epoch basis; updates belonging to more
than one transaction can be sent as part of the same batch.
</p>
<p>
All outstanding updates are applied when the end of an epoch is
reached, even if the updates total less than 32 KB.
</p>
</div>
<a class="indexterm" name="idm46045086058896">
</a>
<a class="indexterm" name="idm46045086057824">
</a>
<p>
Batching can be turned on and off at runtime. To activate it at
runtime, you can use either of these two statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa99975536"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> replica_allow_batching <span class="token operator">=</span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> replica_allow_batching <span class="token operator">=</span> <span class="token keyword">ON</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
If a particular batch causes problems (such as a statement whose
effects do not appear to be replicated correctly), batching can be
deactivated using either of the following statements:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa30714248"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> replica_allow_batching <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>
<span class="token keyword">SET</span> <span class="token keyword">GLOBAL</span> replica_allow_batching <span class="token operator">=</span> <span class="token keyword">OFF</span><span class="token punctuation">;</span></code></pre>
</div>
<p>
You can check whether batching is currently being used by means of
an appropriate
<a class="link" href="show-variables.html" title="15.7.7.41 SHOW VARIABLES Statement">
<code class="literal">
SHOW VARIABLES
</code>
</a>
statement, like this one:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa4905650"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">VARIABLES</span> <span class="token operator">LIKE</span> <span class="token string">'replica%'</span><span class="token punctuation">;</span></code></pre>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/optimizing-innodb-ddl-operations.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="optimizing-innodb-ddl-operations">
</a>
10.5.7 Optimizing InnoDB DDL Operations
</h3>
</div>
</div>
</div>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Many DDL operations on tables and indexes
(
<code class="literal">
CREATE
</code>
,
<code class="literal">
ALTER
</code>
, and
<code class="literal">
DROP
</code>
statements) can be performed online.
See
<a class="xref" href="innodb-online-ddl.html" title="17.12 InnoDB and Online DDL">
Section 17.12, “InnoDB and Online DDL”
</a>
for details.
</p>
</li>
<li class="listitem">
<p>
Online DDL support for adding secondary indexes means that
you can generally speed up the process of creating and
loading a table and associated indexes by creating the table
without secondary indexes, then adding secondary indexes
after the data is loaded.
</p>
</li>
<li class="listitem">
<p>
Use
<a class="link" href="truncate-table.html" title="15.1.37 TRUNCATE TABLE Statement">
<code class="literal">
TRUNCATE TABLE
</code>
</a>
to empty a
table, not
<code class="literal">
DELETE FROM
<em class="replaceable">
<code>
tbl_name
</code>
</em>
</code>
. Foreign key
constraints can make a
<code class="literal">
TRUNCATE
</code>
statement
work like a regular
<code class="literal">
DELETE
</code>
statement, in
which case a sequence of commands like
<a class="link" href="drop-table.html" title="15.1.32 DROP TABLE Statement">
<code class="literal">
DROP TABLE
</code>
</a>
and
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
might be
fastest.
</p>
</li>
<li class="listitem">
<p>
Because the primary key is integral to the storage layout of
each
<code class="literal">
InnoDB
</code>
table, and changing the
definition of the primary key involves reorganizing the
whole table, always set up the primary key as part of the
<a class="link" href="create-table.html" title="15.1.20 CREATE TABLE Statement">
<code class="literal">
CREATE TABLE
</code>
</a>
statement, and
plan ahead so that you do not need to
<code class="literal">
ALTER
</code>
or
<code class="literal">
DROP
</code>
the
primary key afterward.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/pluggable-storage-common-layer.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="pluggable-storage-common-layer">
</a>
18.11.2 The Common Database Server Layer
</h3>
</div>
</div>
</div>
<p>
A MySQL pluggable storage engine is the component in the MySQL
database server that is responsible for performing the actual
data I/O operations for a database as well as enabling and
enforcing certain feature sets that target a specific
application need. A major benefit of using specific storage
engines is that you are only delivered the features needed for a
particular application, and therefore you have less system
overhead in the database, with the end result being more
efficient and higher database performance. This is one of the
reasons that MySQL has always been known to have such high
performance, matching or beating proprietary monolithic
databases in industry standard benchmarks.
</p>
<p>
From a technical perspective, what are some of the unique
supporting infrastructure components that are in a storage
engine? Some of the key feature differentiations include:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<span class="emphasis">
<em>
Concurrency
</em>
</span>
: Some applications have
more granular lock requirements (such as row-level locks)
than others. Choosing the right locking strategy can reduce
overhead and therefore improve overall performance. This
area also includes support for capabilities such as
multi-version concurrency control or
<span class="quote">
“
<span class="quote">
snapshot
</span>
”
</span>
read.
</p>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Transaction Support
</em>
</span>
: Not every
application needs transactions, but for those that do, there
are very well defined requirements such as ACID compliance
and more.
</p>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Referential Integrity
</em>
</span>
: The need to have
the server enforce relational database referential integrity
through DDL defined foreign keys.
</p>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Physical Storage
</em>
</span>
: This involves
everything from the overall page size for tables and indexes
as well as the format used for storing data to physical
disk.
</p>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Index Support
</em>
</span>
: Different application
scenarios tend to benefit from different index strategies.
Each storage engine generally has its own indexing methods,
although some (such as B-tree indexes) are common to nearly
all engines.
</p>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Memory Caches
</em>
</span>
: Different applications
respond better to some memory caching strategies than
others, so although some memory caches are common to all
storage engines (such as those used for user connections),
others are uniquely defined only when a particular storage
engine is put in play.
</p>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Performance Aids
</em>
</span>
: This includes
multiple I/O threads for parallel operations, thread
concurrency, database checkpointing, bulk insert handling,
and more.
</p>
</li>
<li class="listitem">
<p>
<span class="emphasis">
<em>
Miscellaneous Target Features
</em>
</span>
: This may
include support for geospatial operations, security
restrictions for certain data manipulation operations, and
other similar features.
</p>
</li>
</ul>
</div>
<p>
Each set of the pluggable storage engine infrastructure
components are designed to offer a selective set of benefits for
a particular application. Conversely, avoiding a set of
component features helps reduce unnecessary overhead. It stands
to reason that understanding a particular application's set of
requirements and selecting the proper MySQL storage engine can
have a dramatic impact on overall system efficiency and
performance.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/updating-apt-repo.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h2 class="title">
<a name="updating-apt-repo">
</a>
3.9 Upgrading MySQL with the MySQL APT Repository
</h2>
</div>
</div>
</div>
<a class="indexterm" name="idm46045325938368">
</a>
<a class="indexterm" name="idm46045325937328">
</a>
<p>
On Debian and Ubuntu platforms, to perform an in-place upgrade of
MySQL and its components, use the MySQL APT repository. See
<a class="xref" href="linux-installation-apt-repo.html#repo-qg-apt-upgrading" title="Upgrading MySQL with the MySQL APT Repository">
Upgrading MySQL with the MySQL APT Repository
</a>
.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/reset-binary-logs-and-gtids.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="reset-binary-logs-and-gtids">
</a>
15.4.1.2 RESET BINARY LOGS AND GTIDS Statement
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045177855152">
</a>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
This statement takes the place of the old
<code class="literal">
RESET
MASTER
</code>
statement, which is no longer supported.
</p>
</div>
<div class="copytoclipboard-wrapper">
<pre class="programlisting one-line language-sql"><div class="docs-select-all right" id="sa89060994"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">RESET</span> <span class="token datatype">BINARY</span> <span class="token keyword">LOGS</span> <span class="token operator">AND</span> GTIDS <span class="token punctuation">[</span><span class="token keyword">TO</span> <em class="replaceable">binary_log_file_index_number</em><span class="token punctuation">]</span></code></pre>
</div>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
Use this statement with caution to ensure you do not lose any
wanted binary log file data and GTID execution history.
</p>
</div>
<p>
<code class="literal">
RESET BINARY LOGS AND GTIDS
</code>
requires the
<a class="link" href="privileges-provided.html#priv_reload">
<code class="literal">
RELOAD
</code>
</a>
privilege.
</p>
<p>
For a server where binary logging is enabled
(
<a class="link" href="replication-options-binary-log.html#sysvar_log_bin">
<code class="literal">
log_bin
</code>
</a>
is
<code class="literal">
ON
</code>
),
<code class="literal">
RESET BINARY LOGS AND
GTIDS
</code>
deletes all existing binary log files and resets
the binary log index file, resetting the server to its state
before binary logging was started. A new empty binary log file
is created so that binary logging can be restarted.
</p>
<p>
For a server where GTIDs are in use
(
<a class="link" href="replication-options-gtids.html#sysvar_gtid_mode">
<code class="literal">
gtid_mode
</code>
</a>
is
<code class="literal">
ON
</code>
), issuing
<code class="literal">
RESET BINARY LOGS AND
GTIDS
</code>
resets the GTID execution history. The value of
the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_purged">
<code class="literal">
gtid_purged
</code>
</a>
system variable
is set to an empty string (
<code class="literal">
''
</code>
), the global
value (but not the session value) of the
<a class="link" href="replication-options-gtids.html#sysvar_gtid_executed">
<code class="literal">
gtid_executed
</code>
</a>
system variable
is set to an empty string, and the
<code class="literal">
mysql.gtid_executed
</code>
table is cleared (see
<a class="xref" href="replication-gtids-concepts.html#replication-gtids-gtid-executed-table" title="mysql.gtid_executed Table">
mysql.gtid_executed Table
</a>
). If the
GTID-enabled server has binary logging enabled,
<code class="literal">
RESET
BINARY LOGS AND GTIDS
</code>
also resets the binary log as
described above. Note that
<code class="literal">
RESET BINARY LOGS AND
GTIDS
</code>
is the method to reset the GTID execution
history even if the GTID-enabled server is a replica where
binary logging is disabled;
<a class="link" href="reset-replica.html" title="15.4.2.3 RESET REPLICA Statement">
<code class="literal">
RESET
REPLICA
</code>
</a>
has no effect on the GTID execution history.
For more information on resetting the GTID execution history,
see
<a class="xref" href="replication-gtids-lifecycle.html#replication-gtids-execution-history" title="Resetting the GTID Execution History">
Resetting the GTID Execution History
</a>
.
</p>
<p>
Issuing
<code class="literal">
RESET BINARY LOGS AND GTIDS
</code>
without
the optional
<code class="literal">
TO
</code>
clause deletes all binary log
files listed in the index file, resets the binary log index file
to be empty, and creates a new binary log file starting at
<code class="literal">
1
</code>
. Use the optional
<code class="literal">
TO
</code>
clause to start the binary log file index from a number other
than
<code class="literal">
1
</code>
after the reset.
</p>
<p>
Check that you are using a reasonable value for the index
number. If you enter an incorrect value, you can correct this by
issuing another
<code class="literal">
RESET BINARY LOGS AND GTIDS
</code>
statement with or without the
<code class="literal">
TO
</code>
clause. If
you do not correct a value that is out of range, the server
cannot be restarted.
</p>
<p>
The following example demonstrates
<code class="literal">
TO
</code>
clause
usage:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa74476384"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token keyword">RESET</span> <span class="token datatype">BINARY</span> <span class="token keyword">LOGS</span> <span class="token operator">AND</span> GTIDS <span class="token keyword">TO</span> <span class="token number">1234</span><span class="token punctuation">;</span>
<span class="token keyword">SHOW</span> <span class="token datatype">BINARY</span> <span class="token keyword">LOGS</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> Log_name <span class="token punctuation">|</span> File_size <span class="token punctuation">|</span> Encrypted <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> source<span class="token punctuation">-</span>bin.001234 <span class="token punctuation">|</span> 154 <span class="token punctuation">|</span> No <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span></code></pre>
</div>
<div class="important" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Important
</div>
<p>
The effects of
<code class="literal">
RESET BINARY LOGS AND GTIDS
</code>
without the
<code class="literal">
TO
</code>
clause differ from those of
<a class="link" href="purge-binary-logs.html" title="15.4.1.1 PURGE BINARY LOGS Statement">
<code class="literal">
PURGE BINARY LOGS
</code>
</a>
in 2 key
ways:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
<code class="literal">
RESET BINARY LOGS AND GTIDS
</code>
removes
<span class="emphasis">
<em>
all
</em>
</span>
binary log files that are listed
in the index file, leaving only a single, empty binary log
file with a numeric suffix of
<code class="literal">
.000001
</code>
,
whereas the numbering is not reset by
<a class="link" href="purge-binary-logs.html" title="15.4.1.1 PURGE BINARY LOGS Statement">
<code class="literal">
PURGE BINARY LOGS
</code>
</a>
.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
RESET BINARY LOGS AND GTIDS
</code>
is
<span class="emphasis">
<em>
not
</em>
</span>
intended to be used while any
replicas are running. The behavior of
<code class="literal">
RESET
BINARY LOGS AND GTIDS
</code>
when used while replicas
are running is undefined (and thus unsupported), whereas
<a class="link" href="purge-binary-logs.html" title="15.4.1.1 PURGE BINARY LOGS Statement">
<code class="literal">
PURGE BINARY LOGS
</code>
</a>
may be
safely used while replicas are running.
</p>
</li>
</ol>
</div>
<p>
See also
<a class="xref" href="purge-binary-logs.html" title="15.4.1.1 PURGE BINARY LOGS Statement">
Section 15.4.1.1, “PURGE BINARY LOGS Statement”
</a>
.
</p>
</div>
<p>
<code class="literal">
RESET BINARY LOGS AND GTIDS
</code>
without the
<code class="literal">
TO
</code>
clause can prove useful when you first set
up a source and replica, so that you can verify the setup as
follows:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1">
<li class="listitem">
<p>
Start the source and replica, and start replication (see
<a class="xref" href="replication-howto.html" title="19.1.2 Setting Up Binary Log File Position Based Replication">
Section 19.1.2, “Setting Up Binary Log File Position Based Replication”
</a>
).
</p>
</li>
<li class="listitem">
<p>
Execute a few test queries on the source.
</p>
</li>
<li class="listitem">
<p>
Check that the queries were replicated to the replica.
</p>
</li>
<li class="listitem">
<p>
When replication is running correctly, issue
<a class="link" href="stop-replica.html" title="15.4.2.5 STOP REPLICA Statement">
<code class="literal">
STOP REPLICA
</code>
</a>
followed by
<a class="link" href="reset-replica.html" title="15.4.2.3 RESET REPLICA Statement">
<code class="literal">
RESET REPLICA
</code>
</a>
(both on the
replica), then verify that no unwanted data from the test
queries exists on the replica. Following this, issue
<code class="literal">
RESET BINARY LOGS AND GTIDS
</code>
(also on the
replica) to remove binary logs and and associated
transaction IDs.
</p>
</li>
<li class="listitem">
<p>
Remove the unwanted data from the source, then issue
<code class="literal">
RESET BINARY LOGS AND GTIDS
</code>
to purge any
binary log entries and identifiers associated with it.
</p>
</li>
</ol>
</div>
<p>
After verifying the setup, resetting the source and replica and
ensuring that no unwanted data or binary log files generated by
testing remain on the source or replica, you can start the
replica and begin replicating.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/sys-innodb-buffer-stats-by-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="sys-innodb-buffer-stats-by-table">
</a>
30.4.3.8 The innodb_buffer_stats_by_table and x$innodb_buffer_stats_by_table
Views
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045063164736">
</a>
<a class="indexterm" name="idm46045063163280">
</a>
<a class="indexterm" name="idm46045063161776">
</a>
<a class="indexterm" name="idm46045063160272">
</a>
<p>
These views summarize the information in the
<code class="literal">
INFORMATION_SCHEMA
</code>
<a class="link" href="information-schema-innodb-buffer-page-table.html" title="28.4.2 The INFORMATION_SCHEMA INNODB_BUFFER_PAGE Table">
<code class="literal">
INNODB_BUFFER_PAGE
</code>
</a>
table, grouped
by schema and table. By default, rows are sorted by descending
buffer size.
</p>
<div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Warning
</div>
<p>
Querying views that access the
<a class="link" href="information-schema-innodb-buffer-page-table.html" title="28.4.2 The INFORMATION_SCHEMA INNODB_BUFFER_PAGE Table">
<code class="literal">
INNODB_BUFFER_PAGE
</code>
</a>
table can
affect performance. Do not query these views on a production
system unless you are aware of the performance impact and
have determined it to be acceptable. To avoid impacting
performance on a production system, reproduce the issue you
want to investigate and query buffer pool statistics on a
test instance.
</p>
</div>
<p>
The
<a class="link" href="sys-innodb-buffer-stats-by-table.html" title="30.4.3.8 The innodb_buffer_stats_by_table and x$innodb_buffer_stats_by_table Views">
<code class="literal">
innodb_buffer_stats_by_table
</code>
</a>
and
<a class="link" href="sys-innodb-buffer-stats-by-table.html" title="30.4.3.8 The innodb_buffer_stats_by_table and x$innodb_buffer_stats_by_table Views">
<code class="literal">
x$innodb_buffer_stats_by_table
</code>
</a>
views have these columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
object_schema
</code>
</p>
<p>
The schema name for the object, or
<code class="literal">
InnoDB
System
</code>
if the table belongs to the
<code class="literal">
InnoDB
</code>
storage engine.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
object_name
</code>
</p>
<p>
The table name.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
allocated
</code>
</p>
<p>
The total number of bytes allocated for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
data
</code>
</p>
<p>
The number of data bytes allocated for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
pages
</code>
</p>
<p>
The total number of pages allocated for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
pages_hashed
</code>
</p>
<p>
The number of hashed pages allocated for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
pages_old
</code>
</p>
<p>
The number of old pages allocated for the table.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
rows_cached
</code>
</p>
<p>
The number of cached rows for the table.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-ndbinfo-table-fragments.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h4 class="title">
<a name="mysql-cluster-ndbinfo-table-fragments">
</a>
25.6.17.58 The ndbinfo table_fragments Table
</h4>
</div>
</div>
</div>
<a class="indexterm" name="idm46045087730832">
</a>
<p>
The
<code class="literal">
table_fragments
</code>
table provides
information about the fragmentation, partitioning, distribution,
and (internal) replication of
<code class="literal">
NDB
</code>
tables.
</p>
<p>
The
<code class="literal">
table_fragments
</code>
table contains the
following columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
node_id
</code>
</p>
<p>
Node ID (
<a class="ulink" href="/doc/ndb-internals/en/ndb-internals-kernel-blocks-dbdih.html" target="_top">
<code class="literal">
DIH
</code>
</a>
master)
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
table_id
</code>
</p>
<p>
Table ID
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
partition_id
</code>
</p>
<p>
Partition ID
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
fragment_id
</code>
</p>
<p>
Fragment ID (same as partition ID unless table is fully
replicated)
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
partition_order
</code>
</p>
<p>
Order of fragment in partition
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
log_part_id
</code>
</p>
<p>
Log part ID of fragment
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
no_of_replicas
</code>
</p>
<p>
Number of fragment replicas
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
current_primary
</code>
</p>
<p>
Current primary node ID
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
preferred_primary
</code>
</p>
<p>
Preferred primary node ID
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
current_first_backup
</code>
</p>
<p>
Current first backup node ID
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
current_second_backup
</code>
</p>
<p>
Current second backup node ID
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
current_third_backup
</code>
</p>
<p>
Current third backup node ID
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
num_alive_replicas
</code>
</p>
<p>
Current number of live fragment replicas
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
num_dead_replicas
</code>
</p>
<p>
Current number of dead fragment replicas
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
num_lcp_replicas
</code>
</p>
<p>
Number of fragment replicas remaining to be checkpointed
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-foreign-table.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="information-schema-innodb-foreign-table">
</a>
28.4.12 The INFORMATION_SCHEMA INNODB_FOREIGN Table
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045077035104">
</a>
<p>
The
<a class="link" href="information-schema-innodb-foreign-table.html" title="28.4.12 The INFORMATION_SCHEMA INNODB_FOREIGN Table">
<code class="literal">
INNODB_FOREIGN
</code>
</a>
table provides
metadata about
<code class="literal">
InnoDB
</code>
<a class="link" href="glossary.html#glos_foreign_key" title="foreign key">
foreign keys
</a>
.
</p>
<p>
For related usage information and examples, see
<a class="xref" href="innodb-information-schema-system-tables.html" title="17.15.3 InnoDB INFORMATION_SCHEMA Schema Object Tables">
Section 17.15.3, “InnoDB INFORMATION_SCHEMA Schema Object Tables”
</a>
.
</p>
<p>
The
<a class="link" href="information-schema-innodb-foreign-table.html" title="28.4.12 The INFORMATION_SCHEMA INNODB_FOREIGN Table">
<code class="literal">
INNODB_FOREIGN
</code>
</a>
table has these
columns:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<code class="literal">
ID
</code>
</p>
<p>
The name (not a numeric value) of the foreign key index,
preceded by the schema (database) name (for example,
<code class="literal">
test/products_fk
</code>
).
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
FOR_NAME
</code>
</p>
<p>
The name of the
<a class="link" href="glossary.html#glos_child_table" title="child table">
child
table
</a>
in this foreign key relationship.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
REF_NAME
</code>
</p>
<p>
The name of the
<a class="link" href="glossary.html#glos_parent_table" title="parent table">
parent
table
</a>
in this foreign key relationship.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
N_COLS
</code>
</p>
<p>
The number of columns in the foreign key index.
</p>
</li>
<li class="listitem">
<p>
<code class="literal">
TYPE
</code>
</p>
<p>
A collection of bit flags with information about the foreign
key column, ORed together. 0 =
<code class="literal">
ON DELETE/UPDATE
RESTRICT
</code>
, 1 =
<code class="literal">
ON DELETE CASCADE
</code>
,
2 =
<code class="literal">
ON DELETE SET NULL
</code>
, 4 =
<code class="literal">
ON
UPDATE CASCADE
</code>
, 8 =
<code class="literal">
ON UPDATE SET
NULL
</code>
, 16 =
<code class="literal">
ON DELETE NO ACTION
</code>
,
32 =
<code class="literal">
ON UPDATE NO ACTION
</code>
.
</p>
</li>
</ul>
</div>
<h4>
<a name="idm46045077010016">
</a>
Example
</h4>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa609264"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> <span class="token operator">*</span> <span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>INNODB_FOREIGN\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
ID<span class="token punctuation">:</span> test/fk1
FOR_NAME<span class="token punctuation">:</span> test/child
REF_NAME<span class="token punctuation">:</span> test/parent
N_COLS<span class="token punctuation">:</span> 1
TYPE<span class="token punctuation">:</span> 1</span></code></pre>
</div>
<h4>
<a name="idm46045077007520">
</a>
Notes
</h4>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
You must have the
<a class="link" href="privileges-provided.html#priv_process">
<code class="literal">
PROCESS
</code>
</a>
privilege to query this table.
</p>
</li>
<li class="listitem">
<p>
Use the
<code class="literal">
INFORMATION_SCHEMA
</code>
<a class="link" href="information-schema-columns-table.html" title="28.3.8 The INFORMATION_SCHEMA COLUMNS Table">
<code class="literal">
COLUMNS
</code>
</a>
table or the
<a class="link" href="show-columns.html" title="15.7.7.6 SHOW COLUMNS Statement">
<code class="literal">
SHOW COLUMNS
</code>
</a>
statement to view
additional information about the columns of this table,
including data types and default values.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/information-schema-optimization.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="information-schema-optimization">
</a>
10.2.3 Optimizing INFORMATION_SCHEMA Queries
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045227782048">
</a>
<a class="indexterm" name="idm46045227780544">
</a>
<p>
Applications that monitor databases may make frequent use of
<code class="literal">
INFORMATION_SCHEMA
</code>
tables. To write queries
for these tables most efficiently, use the following general
guidelines:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
Try to query only
<code class="literal">
INFORMATION_SCHEMA
</code>
tables that are views on data dictionary tables.
</p>
</li>
<li class="listitem">
<p>
Try to query only for static metadata. Selecting columns or
using retrieval conditions for dynamic metadata along with
static metadata adds overhead to process the dynamic
metadata.
</p>
</li>
</ul>
</div>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
Comparison behavior for database and table names in
<code class="literal">
INFORMATION_SCHEMA
</code>
queries might differ
from what you expect. For details, see
<a class="xref" href="charset-collation-information-schema.html" title="12.8.7 Using Collation in INFORMATION_SCHEMA Searches">
Section 12.8.7, “Using Collation in INFORMATION_SCHEMA Searches”
</a>
.
</p>
</div>
<p>
These
<code class="literal">
INFORMATION_SCHEMA
</code>
tables are
implemented as views on data dictionary tables, so queries on
them retrieve information from the data dictionary:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa87620233"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">CHARACTER_SETS
CHECK_CONSTRAINTS
COLLATIONS
COLLATION_CHARACTER_SET_APPLICABILITY
COLUMNS
EVENTS
FILES
INNODB_COLUMNS
INNODB_DATAFILES
INNODB_FIELDS
INNODB_FOREIGN
INNODB_FOREIGN_COLS
INNODB_INDEXES
INNODB_TABLES
INNODB_TABLESPACES
INNODB_TABLESPACES_BRIEF
INNODB_TABLESTATS
KEY_COLUMN_USAGE
PARAMETERS
PARTITIONS
REFERENTIAL_CONSTRAINTS
RESOURCE_GROUPS
ROUTINES
SCHEMATA
STATISTICS
TABLES
TABLE_CONSTRAINTS
TRIGGERS
VIEWS
VIEW_ROUTINE_USAGE
VIEW_TABLE_USAGE</code></pre>
</div>
<p>
Some types of values, even for a non-view
<code class="literal">
INFORMATION_SCHEMA
</code>
table, are retrieved by
lookups from the data dictionary. This includes values such as
database and table names, table types, and storage engines.
</p>
<p>
Some
<code class="literal">
INFORMATION_SCHEMA
</code>
tables contain
columns that provide table statistics:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-none"><div class="docs-select-all right" id="sa81222058"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-none">STATISTICS.CARDINALITY
TABLES.AUTO_INCREMENT
TABLES.AVG_ROW_LENGTH
TABLES.CHECKSUM
TABLES.CHECK_TIME
TABLES.CREATE_TIME
TABLES.DATA_FREE
TABLES.DATA_LENGTH
TABLES.INDEX_LENGTH
TABLES.MAX_DATA_LENGTH
TABLES.TABLE_ROWS
TABLES.UPDATE_TIME</code></pre>
</div>
<p>
Those columns represent dynamic table metadata; that is,
information that changes as table contents change.
</p>
<p>
By default, MySQL retrieves cached values for those columns from
the
<code class="literal">
mysql.index_stats
</code>
and
<code class="literal">
mysql.innodb_table_stats
</code>
dictionary tables
when the columns are queried, which is more efficient than
retrieving statistics directly from the storage engine. If
cached statistics are not available or have expired, MySQL
retrieves the latest statistics from the storage engine and
caches them in the
<code class="literal">
mysql.index_stats
</code>
and
<code class="literal">
mysql.innodb_table_stats
</code>
dictionary tables.
Subsequent queries retrieve the cached statistics until the
cached statistics expire. A server restart or the first opening
of the
<code class="literal">
mysql.index_stats
</code>
and
<code class="literal">
mysql.innodb_table_stats
</code>
tables do not update
cached statistics automatically.
</p>
<p>
The
<a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
<code class="literal">
information_schema_stats_expiry
</code>
</a>
session variable defines the period of time before cached
statistics expire. The default is 86400 seconds (24 hours), but
the time period can be extended to as much as one year.
</p>
<p>
To update cached values at any time for a given table, use
<a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
<code class="literal">
ANALYZE TABLE
</code>
</a>
.
</p>
<p>
Querying statistics columns does not store or update statistics
in the
<code class="literal">
mysql.index_stats
</code>
and
<code class="literal">
mysql.innodb_table_stats
</code>
dictionary tables
under these circumstances:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
When cached statistics have not expired.
</p>
</li>
<li class="listitem">
<p>
When
<a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
<code class="literal">
information_schema_stats_expiry
</code>
</a>
is set to 0.
</p>
</li>
<li class="listitem">
<p>
When the server is in
<a class="link" href="server-system-variables.html#sysvar_read_only">
<code class="literal">
read_only
</code>
</a>
,
<a class="link" href="server-system-variables.html#sysvar_super_read_only">
<code class="literal">
super_read_only
</code>
</a>
,
<a class="link" href="server-system-variables.html#sysvar_transaction_read_only">
<code class="literal">
transaction_read_only
</code>
</a>
, or
<a class="link" href="innodb-parameters.html#sysvar_innodb_read_only">
<code class="literal">
innodb_read_only
</code>
</a>
mode.
</p>
</li>
<li class="listitem">
<p>
When the query also fetches Performance Schema data.
</p>
</li>
</ul>
</div>
<p>
<a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
<code class="literal">
information_schema_stats_expiry
</code>
</a>
is a session variable, and each client session can define its
own expiration value. Statistics that are retrieved from the
storage engine and cached by one session are available to other
sessions.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<div class="admon-title">
Note
</div>
<p>
If the
<a class="link" href="innodb-parameters.html#sysvar_innodb_read_only">
<code class="literal">
innodb_read_only
</code>
</a>
system variable is enabled,
<a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
<code class="literal">
ANALYZE
TABLE
</code>
</a>
may fail because it cannot update statistics
tables in the data dictionary, which use
<code class="literal">
InnoDB
</code>
. For
<a class="link" href="analyze-table.html" title="15.7.3.1 ANALYZE TABLE Statement">
<code class="literal">
ANALYZE
TABLE
</code>
</a>
operations that update the key distribution,
failure may occur even if the operation updates the table
itself (for example, if it is a
<code class="literal">
MyISAM
</code>
table). To obtain the updated distribution statistics, set
<a class="link" href="server-system-variables.html#sysvar_information_schema_stats_expiry">
<code class="literal">
information_schema_stats_expiry=0
</code>
</a>
.
</p>
</div>
<p>
For
<code class="literal">
INFORMATION_SCHEMA
</code>
tables implemented as
views on data dictionary tables, indexes on the underlying data
dictionary tables permit the optimizer to construct efficient
query execution plans. To see the choices made by the optimizer,
use
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
. To also see the
query used by the server to execute an
<code class="literal">
INFORMATION_SCHEMA
</code>
query, use
<a class="link" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
<code class="literal">
SHOW WARNINGS
</code>
</a>
immediately
following
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
.
</p>
<p>
Consider this statement, which identifies collations for the
<code class="literal">
utf8mb4
</code>
character set:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa43829076"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SELECT</span> COLLATION_NAME
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>COLLATION_CHARACTER_SET_APPLICABILITY
<span class="token keyword">WHERE</span> CHARACTER_SET_NAME <span class="token operator">=</span> <span class="token string">'utf8mb4'</span><span class="token punctuation">;</span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> COLLATION_NAME <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">+</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">-</span><span class="token punctuation">+</span></span>
<span class="token output"><span class="token punctuation">|</span> utf8mb4_general_ci <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> utf8mb4_bin <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> utf8mb4_unicode_ci <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> utf8mb4_icelandic_ci <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> utf8mb4_latvian_ci <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> utf8mb4_romanian_ci <span class="token punctuation">|</span></span>
<span class="token output"><span class="token punctuation">|</span> utf8mb4_slovenian_ci <span class="token punctuation">|</span></span>
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span></code></pre>
</div>
<p>
How does the server process that statement? To find out, use
<a class="link" href="explain.html" title="15.8.2 EXPLAIN Statement">
<code class="literal">
EXPLAIN
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa4207036"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">EXPLAIN</span> <span class="token keyword">SELECT</span> COLLATION_NAME
<span class="token keyword">FROM</span> INFORMATION_SCHEMA<span class="token punctuation">.</span>COLLATION_CHARACTER_SET_APPLICABILITY
<span class="token keyword">WHERE</span> CHARACTER_SET_NAME <span class="token operator">=</span> <span class="token string">'utf8mb4'</span>\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
id<span class="token punctuation">:</span> 1
select_type<span class="token punctuation">:</span> SIMPLE
table<span class="token punctuation">:</span> cs
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> const
possible_keys<span class="token punctuation">:</span> PRIMARY,name
key<span class="token punctuation">:</span> name
key_len<span class="token punctuation">:</span> 194
ref<span class="token punctuation">:</span> const
rows<span class="token punctuation">:</span> 1
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> Using index
<span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 2. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
id<span class="token punctuation">:</span> 1
select_type<span class="token punctuation">:</span> SIMPLE
table<span class="token punctuation">:</span> col
partitions<span class="token punctuation">:</span> NULL
type<span class="token punctuation">:</span> ref
possible_keys<span class="token punctuation">:</span> character_set_id
key<span class="token punctuation">:</span> character_set_id
key_len<span class="token punctuation">:</span> 8
ref<span class="token punctuation">:</span> const
rows<span class="token punctuation">:</span> 68
filtered<span class="token punctuation">:</span> 100.00
Extra<span class="token punctuation">:</span> NULL
</span><span class="token output">2 rows in set, 1 warning (0.01 sec)</span></code></pre>
</div>
<p>
To see the query used to satisfy that statement, use
<a class="link" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
<code class="literal">
SHOW WARNINGS
</code>
</a>
:
</p>
<div class="copytoclipboard-wrapper">
<pre class="programlisting language-sql"><div class="docs-select-all right" id="sa17703466"><div class="copy-help left">Press ⌘+C to copy</div> <div class="right"><button class="clipboard-btn" title="Copy to Clipboard"><span class="icon-clipboard"></span></button></div></div><code class="language-sql"><span class="token prompt">mysql></span> <span class="token keyword">SHOW</span> <span class="token keyword">WARNINGS</span>\G
<span class="token output"><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span> 1. row <span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span><span class="token punctuation">*</span>
Level<span class="token punctuation">:</span> Note
Code<span class="token punctuation">:</span> 1003
Message<span class="token punctuation">:</span> /<span class="token punctuation">*</span> select#1 <span class="token punctuation">*</span>/ select `mysql`.`col`.`name` AS `COLLATION_NAME`
from `mysql`.`character_sets` `cs`
join `mysql`.`collations` `col`
where ((`mysql`.`col`.`character_set_id` = '45')
and ('utf8mb4' = 'utf8mb4'))</span></code></pre>
</div>
<p>
As indicated by
<a class="link" href="show-warnings.html" title="15.7.7.42 SHOW WARNINGS Statement">
<code class="literal">
SHOW WARNINGS
</code>
</a>
,
the server handles the query on
<a class="link" href="information-schema-collation-character-set-applicability-table.html" title="28.3.7 The INFORMATION_SCHEMA COLLATION_CHARACTER_SET_APPLICABILITY Table">
<code class="literal">
COLLATION_CHARACTER_SET_APPLICABILITY
</code>
</a>
as a query on the
<code class="literal">
character_sets
</code>
and
<code class="literal">
collations
</code>
data dictionary tables in the
<code class="literal">
mysql
</code>
system database.
</p>
</div>
<br/>
</div>
|
https://dev.mysql.com/doc/refman/8.4/en/event-scheduler-thread-states.html | <div id="docs-body">
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title">
<a name="event-scheduler-thread-states">
</a>
10.14.9 Event Scheduler Thread States
</h3>
</div>
</div>
</div>
<a class="indexterm" name="idm46045220941504">
</a>
<a class="indexterm" name="idm46045220940016">
</a>
<p>
These states occur for the Event Scheduler thread, threads that
are created to execute scheduled events, or threads that
terminate the scheduler.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p>
<a class="indexterm" name="idm46045220937184">
</a>
<a class="indexterm" name="idm46045220935696">
</a>
<code class="literal">
Clearing
</code>
</p>
<p>
The scheduler thread or a thread that was executing an event
is terminating and is about to end.
</p>
</li>
<li class="listitem">
<p>
<a class="indexterm" name="idm46045220932224">
</a>
<a class="indexterm" name="idm46045220930736">
</a>
<code class="literal">
Initialized
</code>
</p>
<p>
The scheduler thread or a thread that executes an event has
been initialized.
</p>
</li>
<li class="listitem">
<p>
<a class="indexterm" name="idm46045220927280">
</a>
<a class="indexterm" name="idm46045220925776">
</a>
<code class="literal">
Waiting for next activation
</code>
</p>
<p>
The scheduler has a nonempty event queue but the next
activation is in the future.
</p>
</li>
<li class="listitem">
<p>
<a class="indexterm" name="idm46045220922288">
</a>
<a class="indexterm" name="idm46045220920784">
</a>
<code class="literal">
Waiting for scheduler to stop
</code>
</p>
<p>
The thread issued
<code class="literal">
SET GLOBAL
event_scheduler=OFF
</code>
and is waiting for the
scheduler to stop.
</p>
</li>
<li class="listitem">
<p>
<a class="indexterm" name="idm46045220916576">
</a>
<a class="indexterm" name="idm46045220915088">
</a>
<code class="literal">
Waiting on empty queue
</code>
</p>
<p>
The scheduler's event queue is empty and it is
sleeping.
</p>
</li>
</ul>
</div>
</div>
<br/>
</div>
|
Subsets and Splits