2009/9/1 Sam Mason <s...@samason.me.uk>: > 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.
it's question. You ask, is it (NULL, NULL) same as NULL. Without some reduction - ROW(NULL, NULL) is really different than NULL. Pavel > > -- > 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 > -- Sent via pgsql-bugs mailing list (pgsql-bugs@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-bugs
