EXISTS predicate

The exists predicate tests for the presence or absence of a condition specified by a subselect.

Use the following syntax:

EXISTS ( subselect )

EXISTS collection-valued-path-expression

The result of EXISTS is true if the subselect returns at least one value or the path expression evaluates to a nonempty collection, otherwise the result is false.

To negate an EXISTS predicate, precede it with the logical operator NOT.

Example: EXISTS predicate

Return departments that have at least one employee earning more than 1000000:

SELECT OBJECT(d) FROM DeptBean d WHERE EXISTS ( SELECT 1 FROM IN (d.emps) e WHERE e.salary > 1000000 )

Return departments that have no employees:

SELECT OBJECT(d) FROM DeptBean d WHERE NOT EXISTS ( SELECT 1 FROM IN (d.emps) e)

The previous query can also be written as follows:

SELECT OBJECT(d) FROM DeptBean d WHERE NOT EXISTS d.emps

Related concepts

EJB query language

WHERE clause

Related tasks

Use EJB query