Date: Tue, 26 Oct 2004 23:01:29 +0200
To: Stephan Szabo <sszabo@megazone.bigpanda.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: How do you compare (NULL) and (non-NULL)?
Message-ID: <20041026210129.GC5922@localhost.localdomain>
References: <417EB238.1000109@kencast.com>
	<20041026134508.N5021@megazone.bigpanda.com>
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From: Jerome Alet <alet@librelogiciel.com>

On Tue, Oct 26, 2004 at 01:48:48PM -0700, Stephan Szabo wrote:
> On Tue, 26 Oct 2004, Wei Weng wrote:
> 
> > In the following query
> >
> > SELECT Parent FROM Channels ORDER BY Parent ASC;
> >
> > If I have a couple of (NULL)s in the field [Parent], they will be listed at
> > the bottom of the query result.
> >
> > Is it because PostgreSQL considers (NULL) as the biggest value? If I run the
> > same query under MSSQL Server 2000, I get the exact opposite result
> > regarding the order of (NULL)s and (non-NULL) values. They are listed at the
> > very beginning of the query result.

you could try to use COALESCE to treat NULLs as either a minimal or
maximal value so that your ordering is correct :

SELECT Parent FROM Channels ORDER BY COALESCE(Parent, -1) ASC;

to treat NULLs as -1 for example

hth

Jerome Alet