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SQL Anywhere 12.0.0 (Français) » SQL Anywhere Server - SQL Usage » Querying and modifying data » Using subqueries » Testing subqueries


Subqueries and the EXISTS test

Subqueries used in the subquery comparison test and set membership test both return data values from the subquery table. Sometimes, however, you may be more concerned with whether the subquery returns any results, rather than which results. The existence test (EXISTS) checks whether a subquery produces any rows of query results. If the subquery produces one or more rows of results, the EXISTS test returns TRUE. Otherwise, it returns FALSE.

 Explanation of the existence test
 Negating the existence test
 Correlated subqueries