EXISTS predicate

>>-EXISTS--( fullselect )--------------------------------------><
The EXISTS predicate tests for the existence
of certain rows. The fullselect may specify any number of columns, and
- The result is true only if the number of rows specified by
the fullselect is not zero.
- The result is false only if the number of rows specified by
the fullselect is zero.
- The result cannot be unknown.
The values returned by the fullselect are ignored.
Example
EXISTS (SELECT *
FROM EMPLOYEE WHERE SALARY > 60000)
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