An EXISTS predicate tests whether or not the result table
specified in a column select expression is empty.
(B)0[m[1mexists-predicate = [m
[1m [m
[1mqqq> [1;4mEXISTS[m[1m ( select-expr ) qqqqqqq> [m
If the result table specified in the select expression has one or
more rows, SQL evaluates the EXISTS predicate as true. Otherwise,
the predicate is false. An EXISTS predicate cannot be unknown.
Because it only checks for the existence of rows, an EXISTS
predicate does not require that the result table from its column
select expression be a single column wide (see Column_Select_
Expressions for details on column select expressions). For
EXISTS predicates, an asterisk (*) wildcard in the column select
expression can refer to a multicolumn table .