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Null comparisons (was Re: checksum)

From: Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com>
To: Mike Rylander <mrylander(at)gmail(dot)com>
Cc: David Helgason <david(at)uti(dot)is>,Federico Balbi <fbalbi(at)cs(dot)utsa(dot)edu>,postgresql-general <pgsql-general(at)postgresql(dot)org>
Subject: Null comparisons (was Re: checksum)
Date: 2004-09-27 14:47:37
Message-ID: 20040927074416.C70916@megazone.bigpanda.com (view raw or flat)
Thread:
Lists: pgsql-general
On Mon, 27 Sep 2004, Mike Rylander wrote:

> On Sun, 26 Sep 2004 20:16:52 +0200, David Helgason <david(at)uti(dot)is> wrote:

> > On a similar note, I've found myself wanting an extended '=' operator
> > meaning
> >         (a = b or (a is null and b is null))
> >
>
> Setting 'transform_null_equals' to true in postgresql.conf should do
> what you want.

Unfortunately, it probably won't.  That only changes the explicit token
sequence = NULL into an IS NULL, it won't help if you're doing a=b where a
or b may be NULL.

The original does appear to be equivalent to "not(a is distinct from b)",
although I'm not sure that's necessarily easier to use than the above.

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