Progress
SQL-92
Guide and Reference


EXISTS Predicate

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.

This is the syntax for an exists_predicate:

SYNTAX
EXISTS (query_expression) 

EXAMPLE

In this example, the predicate evaluates to true if the specified customer has any orders:

EXISTS (SELECT * FROM order_tbl
     WHERE order_tbl.custid = ’888’ ;) 


Copyright © 2004 Progress Software Corporation
www.progress.com
Voice: (781) 280-4000
Fax: (781) 280-4095