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Message-ID: <4427F351.5010303@logix-tt.com>
Date: Mon, 27 Mar 2006 16:14:41 +0200
From: Markus Schaber <schabi@logix-tt.com>
Organization: Logical Tracking and Tracing International AG, Switzerland
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To: Weimao Ke <wke@indiana.edu>
Cc: Michael Fuhr <mike@fuhr.org>, pgsql-sql@postgresql.org
Subject: Re: pgsql aggregate: conditional max
References: <4413AD1C.9050604@indiana.edu>
	<20060312054212.GA25423@winnie.fuhr.org>
	<44145569.3010208@indiana.edu>
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Hi, Weimao Ke,

Weimao Ke wrote:
>> SELECT aid, cat
>> FROM tablename AS t
>> JOIN (SELECT aid, max(weight) AS weight
>>      FROM tablename
>>      GROUP BY aid) AS s USING (aid, weight);
>>
> This query will return duplicates if there are multiple categories (for
> one aid) with the same max weight. Yet, I should be able to remove the
> duplicates somehow...:)

Try

SELECT DISTINCT aid, cat
FROM tablename AS t
JOIN (SELECT aid, max(weight) AS weight
     FROM tablename
     GROUP BY aid) AS s USING (aid, weight);

HTH,
Markus


-- 
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

Fight against software patents in EU! www.ffii.org www.nosoftwarepatents.org