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Re: What's wrong with this query?

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Thanks all, that's pretty much what I figured - just wanted to make sure..  I'm still trying to master this SQL thing you speak of.

On Sun, Jun 21, 2009 at 5:20 PM, Martin Gainty <mgainty@xxxxxxxxxxx> wrote:
testcase for a null uuid?

thanks,
Martin
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> To: pgsql-general@xxxxxxxxxxxxxx
> From: spam_eater@xxxxxxx
> Subject: Re: What's wrong with this query?
> Date: Mon, 22 Jun 2009 00:37:41 +0200

>
> Mike Christensen wrote on 22.06.2009 00:10:
> > I just tracked down a bug in my software due to an "unexpected" behavior
> > in Postgres.. Can someone clarify why this doesn't work (I haven't
> > tried it on MSSQL or anything else, so I'm not sure if this is the
> > official SQL standard or anything)..
> >
> > CREATE TABLE test
> > (
> > value uuid
> > );
> >
> > INSERT INTO test VALUES ('00000000-0000-0000-0000-000000000000');
> > INSERT INTO test VALUES ('11111111-1111-1111-1111-111111111111');
> > INSERT INTO test VALUES (null);
> >
> > select * from test where value != '00000000-0000-0000-0000-000000000000';
> >
> > What I expect to get is two rows: the
> > '11111111-1111-1111-1111-111111111111' row and the null row, as both
> > those values are in fact not '00000000-0000-0000-0000-000000000000'.
> > However, I only get the first one.
> >
> That is standard behaviour.
> A comparison with a NULL value always returns false (and that is not a Postgres
> speciality).
>
> You need to use
>
> select *
> from test
> where value != '00000000-0000-0000-0000-000000000000'
> or value is null;
>
> Thomas
>
>
> --
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