On Mon, Aug 31, 2009 at 07:26:59PM +0200, Pavel Stehule wrote: > 2009/8/31 Sam Mason <s...@samason.me.uk>: > > The more awkward case (to me anyway) is that the standard says (1,NULL) > > IS NULL should evaluate to TRUE. > > what? > > only (NULL, NULL) IS NULL is true
Bah, sorry you're right! I was rattling my favorite tin and getting mixed up with the behavior with IS NOT NULL, the negation of which would say this row is null. I.e: SELECT NOT (1,NULL) IS NOT NULL; evaluates to TRUE. I think the consensus is that we should continue to follow the spec on this, but I was getting confused as to which operator contains the EXISTS and FORALL operator. I.e. a value "v" IS NULL iff all elements of "v" are not 'the null value', whereas "v" IS NOT NULL iff an element of "v" is 'the null value'. > p.s. what isn't consistent (maybe - there are more possible > interpretations) is > > (NULL, NULL) IS DISTINCT FROM NULL is true Yup, I'd agree with Merlin that a ROW consisting entirely of 'null values' should itself be 'the null value' (to use the terminology from the copy of the SQL spec I'm reading). I think this should also work recursively: SELECT ROW(ROW(NULL)) IS DISTINCT FROM NULL; should return FALSE, in my understanding. -- Sam http://samason.me.uk/ -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
