EXISTS predicate ; sql

DB

snippet from reference

8.8  <exists predicate>

Function
Specify a test for a non-empty set.

Format
<exists predicate> ::= EXISTS <table subquery>

General Rules

1) Let T be the result of the <table subquery>.

2) If the cardinality of T is greater than 0, then the result of
   the <exists predicate> is true; otherwise, the result of the
   <exists predicate> is false.

reference

Carnegie Mellon University, Computer Club, sql, sql1992.txt

at 8.8 <exists predicate>

note

  • SQL-92 is obsoleted
  • check yourself latest SQL-2011
  • latest is in ISO/IEC 9075 and non-free

extra

predicate

cardinality