Question; Answer; Project
What is the aggregate function singleValueOrNull used to implement?; subquery operators; ClickHouse
What checks if there is only one unique non-NULL value in the data?; singleValueOrNull; ClickHouse
If there are zero or at least two distinct values, what does singleValueOrNull return?; NULL; ClickHouse
What is the unique value if there is only one unique non-NULL value in x?; NULL; ClickHouse