Message-ID: <412CD247.5020706@sympatico.ca>
Date: Wed, 25 Aug 2004 13:54:15 -0400
From: Jean-Luc Lachance <jllachan@sympatico.ca>
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To: Andrew Perrin <clists@perrin.socsci.unc.edu>
Cc: pgsql-sql@postgresql.org
Subject: Re: Complicated "group by" question
References: <Pine.LNX.4.53.0408251300580.20106@perrin.socsci.unc.edu>
In-Reply-To: <Pine.LNX.4.53.0408251300580.20106@perrin.socsci.unc.edu>
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Andrew,

If assing is not a many to many relation,
why did you not fold accept_id into assign?

Any way, here is the query you need:

select assign.reviewer_id, ss.max_assign_date,
   accept.assign_id, accept.accept_id
from (
   select reviewer_id, max( assign_date) as max_assign_date
   from assign group by reviewer_id) as ss, assign, accept
where ss.reviewer_id = assign.reviewer_id
   and ss.max_assign_date = assign.assign_date
   and assign.assign_id = accept.assign_id;


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
> 		...		...
> 
> 
> Thanks for any guidance.
> 
> Andy
> 
> ----------------------------------------------------------------------
> Andrew J Perrin - http://www.unc.edu/~aperrin
> Assistant Professor of Sociology, U of North Carolina, Chapel Hill
> clists@perrin.socsci.unc.edu * andrew_perrin (at) unc.edu
> 
> 
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