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828 B
828 B
EXISTS
The EXISTS
operator checks how many records are in the result of a subquery. If it is empty, then the operator returns 0
. Otherwise, it returns 1
.
EXISTS
can be used in a WHERE clause.
!!! warning "Warning" References to main query tables and columns are not supported in a subquery.
Syntax
WHERE EXISTS(subquery)
Example
Query:
SELECT 'Exists' WHERE EXISTS (SELECT * FROM numbers(10) WHERE number < 2);
SELECT 'Empty subquery' WHERE EXISTS (SELECT * FROM numbers(10) WHERE number > 12);
The first query returns one row while the second query does not return rows because the result of the subquery is empty:
┌─'Exists'─┐
│ Exists │
└──────────┘