"Dann Corbit" <DCorbit@xxxxxxxxx> writes: > Or (perhaps better yet, violating trichotomy) ... > If <Some_column> has a null numeric value, then ALL of the following are > FALSE for that case: > Some_column < 0 > Some_column > 0 > Some_column = 0 > Some_column <> 0 // This is the one that many find surprising > Some_column <= 0 > Some_column >= 0 It's worse than that: the above do *not* yield FALSE, they yield NULL. Which does act like FALSE in a simple WHERE clause, but there are other cases (like CHECK clauses) where it doesn't. "x NOT IN (SELECT ...)" is a case that newbies routinely get bitten by. > Even at that, I think that being able to insert more than one null value > into a unique index should be considered as a bug (or diagnosed as an > error). Direct your complaints to the ISO SQL standards committee. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
