From: | Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com> |
---|---|
To: | Patrick Narkinsky <patrick(at)narkinsky(dot)com> |
Cc: | pgsql-bugs(at)postgresql(dot)org |
Subject: | Re: BUG #2334: WHERE IN (SUBSELECT) fails when column is null |
Date: | 2006-03-19 00:13:49 |
Message-ID: | 20060318161050.V82070@megazone.bigpanda.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-bugs |
On Fri, 17 Mar 2006, Patrick Narkinsky wrote:
> This may be expected behavior, but it certainly doesn't seem right to me,
> and it works as expected in sqlite.
>
> The database is as follows:
>
> BEGIN TRANSACTION;
> create table a (
> id integer,
> text varchar(20)
> );
> INSERT INTO a VALUES(0,'test');
> INSERT INTO a VALUES(1,'test2');
> create table b (
> id integer,
> a_id integer);
> INSERT INTO b VALUES(0,NULL);
> INSERT INTO b VALUES(1,NULL);
> INSERT INTO b VALUES(2,NULL);
> COMMIT;
>
> The following query returns everything in a in sqlite, but returns nothing
> in postgresql:
>
> select * from a where a.id not in (select a_id from b);
AFAICS, our behavior follows SQL.
a NOT IN b is NOT(a IN b)
IN is defined in terms of = ANY.
a =ANY (b) is basically (by my reading of 8.8 anyway):
True if a = bi for some bi in b
False if b is empty or a <> bi for all bi in b
Unknown otherwise
Since a <> NULL returns unknown, the second one won't come up, so the
whole expression won't ever be true after the negation. It might be false
or it might be unknown.
From | Date | Subject | |
---|---|---|---|
Next Message | Bruce Momjian | 2006-03-19 02:10:22 | Re: BUG #2333: dropdb ignores the database name argument |
Previous Message | Neil Conway | 2006-03-18 22:11:56 | Re: [PATCHES] Bonjour registration on Intel Macs is broken |