On 2019-08-12 10:55, Svein Erling Tysvær [email protected] [firebird-support] wrote: > I certainly agree with you that if EXISTS returns false, then NOT > EXISTS should return true. It could make some sense if both EXISTS and > NOT EXISTS returned <null> (though it should be documented somewhere), > but not that one returns false and the other <null>. When you write > this in the tracker, I think it would be good if you included a very > simple reproducible test case.
EXISTS (nor NOT EXISTS) cannot and should not ever produce NULL. If it does, then that is a bug. SQL:2016 says: """ 1) Let T be the result of the <table subquery>. 2) If the cardinality of T is greater than 0 (zero), then the result of the <exists predicate> is True; otherwise, the result of the <exists predicate> is False. """ Mark
