Re: Bug #765: 'IS NULL' versus '= NULL'

On Sat, Sep 14, 2002 at 04:43:15AM -0400, pgsql-bugs@postgresql.org wrote:
> Eventhough my_table contain a record with id as null, the last 2 sqls
> are not resulting that record. Why? Maybe my understanding would be
> wrong on this behaviour, if so please kindly apologize and give some
> description on this difference, since i dont have answer in the
> documentation.

afaik: according to sql documentation (and implementations different
that postgresql), any comparison where one of values is null should
yield "null" as response. is means, that NULL =3D NULL gives you "null"
instead of "true", and if you want this kind of checks you have to use
"is null" operator.

postgresql used to process "NULL =3D NULL" as true, but it was changed to
conform with standard and typical implementations in ohter databases.

best regards

depesz

--=20
hubert depesz lubaczewski                          http://www.depesz.pl/
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M=F3j Bo=BFe, spraw abym milcza=B3, dop=F3ki si=EA nie upewni=EA,  =BFe  na=
prawd=EA  mam
co=B6 do powiedzenia.                                      (c) 1998 depesz