From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Gaetano Mendola <mendola@bigfoot.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Select the max on a field
Date: Thu, 12 Sep 2002 07:02:06 -0700 (PDT)
Message-ID: <20020912065516.L45340-100000@megazone23.bigpanda.com> (raw)
In-Reply-To: <alq3mr$2s7o$1@news.hub.org>
On Thu, 12 Sep 2002, Gaetano Mendola wrote:
> Hi all,
>
> Suppose that I have a table like this:
>
>
> att_1 | att_2 | att_3 | att_4
> --------------------------------
> 1 | a | y | y1
> 2 | b | y | y2
> 3 | a | xx | y3
> 4 | c | zz | y4
> 5 | a | t | y5
> 6 | c | x | y6
>
>
>
> I want obtain all row that have for each att_2
> the max of att_1
>
> some like
>
> SELECT *
> FROM MY_TABLE
> GROUP BY att_2
> HAVING att_1 = max ( id_user_log)
If you don't mind using postgres extensions and
don't need a particular att_1 ordering:
select distinct on (att_2) * from test
order by att_2, att_1 desc;
Otherwise I'm not sure you can do it without
a subselect somewhere.
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To: pgsql-sql@postgresql.org
Cc: sszabo@megazone23.bigpanda.com, mendola@bigfoot.com
Subject: Re: Select the max on a field
In-Reply-To: <20020912065516.L45340-100000@megazone23.bigpanda.com>
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