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* order by date desc but NULLs last
@ 2003-02-09 22:29 A.M. <agentm@cmu.edu>
0 siblings, 2 replies; 5+ messages in thread
From: A.M. @ 2003-02-09 22:29 UTC (permalink / raw)
To: pgsql-sql
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.)
Thanks for any advice.
><><><><><><><><><
AgentM
agentm@cmu.edu
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: order by date desc but NULLs last
@ 2003-02-09 23:12 Ross J. Reedstrom <reedstrm@rice.edu>
parent: A.M. <agentm@cmu.edu>
1 sibling, 1 reply; 5+ messages in thread
From: Ross J. Reedstrom @ 2003-02-09 23:12 UTC (permalink / raw)
To: A.M. <agentm@cmu.edu>; +Cc: pgsql-sql
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
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: order by date desc but NULLs last
@ 2003-02-09 23:12 Tomasz Myrta <jasiek@klaster.net>
parent: A.M. <agentm@cmu.edu>
1 sibling, 0 replies; 5+ messages in thread
From: Tomasz Myrta @ 2003-02-09 23:12 UTC (permalink / raw)
To: A.M. <agentm@cmu.edu>; pgsql-sql
> 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.)
>
> Thanks for any advice.
> ><><><><><><><><><
> AgentM
> agentm@cmu.edu
order by gradetime is null asc, gradetime desc;
Regards,
Tomasz Myrta
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: order by date desc but NULLs last
@ 2003-02-10 18:32 Jean-Luc Lachance <jllachan@nsd.ca>
parent: Ross J. Reedstrom <reedstrm@rice.edu>
0 siblings, 1 reply; 5+ messages in thread
From: Jean-Luc Lachance @ 2003-02-10 18:32 UTC (permalink / raw)
To: Ross J. Reedstrom <reedstrm@rice.edu>; +Cc: A.M. <agentm@cmu.edu>; pgsql-sql
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
>
> ---------------------------(end of broadcast)---------------------------
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^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: order by date desc but NULLs last
@ 2003-02-10 18:52 Ross J. Reedstrom <reedstrm@rice.edu>
parent: Jean-Luc Lachance <jllachan@nsd.ca>
0 siblings, 0 replies; 5+ messages in thread
From: Ross J. Reedstrom @ 2003-02-10 18:52 UTC (permalink / raw)
To: Jean-Luc Lachance <jllachan@nsd.ca>; +Cc: A.M. <agentm@cmu.edu>; pgsql-sql
On Mon, Feb 10, 2003 at 01:32:54PM -0500, Jean-Luc Lachance wrote:
> Why not try the obvious first?
Because it's not always obvious ;-) Yup, if you want two kinds of order
(NULLs last, descending dates), use two order by clauses.
> order by gradedtime is null, gradedtime desc;
>
> "Ross J. Reedstrom" wrote:
<a different, less elegant way to get the NULLs last>
Ross
^ permalink raw reply [nested|flat] 5+ messages in thread
end of thread, other threads:[~2003-02-10 18:52 UTC | newest]
Thread overview: 5+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2003-02-09 22:29 order by date desc but NULLs last A.M. <agentm@cmu.edu>
2003-02-09 23:12 ` Ross J. Reedstrom <reedstrm@rice.edu>
2003-02-10 18:32 ` Jean-Luc Lachance <jllachan@nsd.ca>
2003-02-10 18:52 ` Ross J. Reedstrom <reedstrm@rice.edu>
2003-02-09 23:12 ` Tomasz Myrta <jasiek@klaster.net>
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