The EXISTS predicate can be used to check for the existence of specific rows. The query_expression returns rows rather than values. The predicate evaluates to true if the number of rows returned by the query_expression is nonzero.
Syntax
This is the syntax for an EXISTS predicate:
EXISTS (query_expression)
Example
In this example, the predicate returns the item names of all items which contain sub-items:
SELECT itemname FROM pub.mtitem
WHERE EXISTS(SELECT subitem FROM pub.mtitem);
