From: Jean-Luc Lachance <jllachan@nsd.ca>
To: Ross J. Reedstrom <reedstrm@rice.edu>
Cc: A.M. <agentm@cmu.edu>
Cc: pgsql-sql@postgresql.org
Subject: Re: order by date desc but NULLs last
Date: Mon, 10 Feb 2003 13:32:54 -0500
Message-ID: <3E47F056.DE8707E2@nsd.ca> (raw)
References: <F427C52A-3C7D-11D7-A094-0030657192DA@cmu.edu>
<20030209231204.GB11550@wallace.ece.rice.edu>
Why not try the obvious first?
order by gradedtime is null, gradedtime desc;
"Ross J. Reedstrom" wrote:
>
> On Sun, Feb 09, 2003 at 05:29:29PM -0500, A.M. wrote:
> > I have a simple query that sorts by descending date but the NULL dates
> > show up first. Is there a way I can sort so they come last without
> > sorting ascending?
> >
> > SELECT submittime,score,gradedtime FROM student_gradedmaterial WHERE
> > gradedmaterialid=3 and studentid=102 order by gradedtime desc;
> >
> > submittime | score | gradedtime
> > ---------------------+-------+----------------------------
> > 2003-01-30 22:56:38 | |
> > 2003-01-31 03:42:29 | 99 | 2003-02-06 14:21:43.043587
> >
> > but what I want is all the graded items first in gradedtime desc and
> > NULL afterwards. I do need to keep the NULL score rows. (So I get the
> > latest submitted grade for the assignment but also any ungraded
> > submission information.)
>
> You need to ORDER BY a _function_ of the gradedtime column, substituting
> an extreme value for NULL. Try this:
>
> SELECT submittime,score,gradedtime FROM student_gradedmaterial
> WHERE gradedmaterialid=3 and studentid=102 order by
> coalesce(gradedtime,'-infinity') desc;
>
> Ross
>
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To: pgsql-sql@postgresql.org
Cc: jllachan@nsd.ca, reedstrm@rice.edu, agentm@cmu.edu
Subject: Re: order by date desc but NULLs last
In-Reply-To: <3E47F056.DE8707E2@nsd.ca>
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