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Re: Complicated "group by" question

From: Jean-Luc Lachance <jllachan(at)sympatico(dot)ca>
To: Andrew Perrin <clists(at)perrin(dot)socsci(dot)unc(dot)edu>
Cc: pgsql-sql(at)postgresql(dot)org
Subject: Re: Complicated "group by" question
Date: 2004-08-25 17:54:15
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-sql

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 -
> Assistant Professor of Sociology, U of North Carolina, Chapel Hill
> clists(at)perrin(dot)socsci(dot)unc(dot)edu * andrew_perrin (at)
> ---------------------------(end of broadcast)---------------------------
> TIP 1: subscribe and unsubscribe commands go to majordomo(at)postgresql(dot)org

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Next:From: Andrew PerrinDate: 2004-08-25 18:20:52
Subject: Re: Complicated "group by" question
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Subject: Re: Complicated "group by" question

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