From: Jeff Boes <jboes@qtm.net>
To: pgsql-sql@postgresql.org
Subject: Re: Complicated "group by" question
Date: Thu, 02 Sep 2004 10:39:36 -0400
Message-ID: <IgGZc.92877$JG7.85347@hydra.nntpserver.com> (raw)
In-Reply-To: <Pine.LNX.4.53.0408251300580.20106@perrin.socsci.unc.edu>
References: <Pine.LNX.4.53.0408251300580.20106@perrin.socsci.unc.edu>
Andrew Perrin wrote:
> I have a table of people ("reviewers"), a table of review assignments
> ("assign"), and a table of review acceptances ("accept"). I would like to
> be able to write a query to return the latest (e.g., max(assign_date))
> assignment for each reviewer, plus the acc_id field from "accept". I
> think I should be able to do this with a GROUP BY clause, but am having no
> luck.
>
> Table structure:
>
> reviewers assign accept
> -----------------------------------------
> reviewer_id assign_id accept_id
> reviewer_id assign_id
> ... assign_date
> ... ...
>
I think you want to write a non-GROUPed query using "DISTINCT ON".
Something like this:
SELECT DISTINCT ON (reviewer_id,assign_id)
reviewer_id,
assign_id,
assign_date,
accept_id
FROM reviewers
JOIN assign USING (reviewer_id)
JOIN accept USING (accept_id)
ORDER BY reviewer_id, assign_id, assign_date DESC;
--
(Posted from an account used as a SPAM dump. If you really want to get
in touch with me, dump the 'jboes' and substitute 'mur'.)
________
Jeffery Boes <>< jboes@qtm.net
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To: pgsql-sql@postgresql.org
Cc: jboes@qtm.net
Subject: Re: Complicated "group by" question
In-Reply-To: <IgGZc.92877$JG7.85347@hydra.nntpserver.com>
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