Re: For each key, find row with highest value of other field

From: "Fernando Hevia" <fhevia(at)ip-tel(dot)com(dot)ar>
To: <raju(at)linux-delhi(dot)org>, <pgsql-sql(at)postgresql(dot)org>
Subject: Re: For each key, find row with highest value of other field
Date: 2008-10-03 19:19:04
Message-ID: 062a01c9258c$e65aa880$8f01010a@iptel.com.ar
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> Raj Mathur wrote:
>
> I have some data of the form:
>
> Key | Date | Value
> A | 2008-05-01 | foo *
> A | 2008-04-01 | bar
> A | 2008-03-01 | foo *
> B | 2008-03-04 | baz
> B | 2008-02-04 | bar
> C | 2008-06-03 | foo *
> C | 2008-04-04 | baz
> C | 2008-03-04 | bar
>
> Is there any way to select only the rows marked with a (*)
> out of these without doing a join? I.e. I wish to find the
> row with the highest Date for each Key and use the Value from that.
>

This should do it:

Select value
from table a
where date = (select max(b.date) from table b where b.key = a.key) q;

Regards,
Fernando.

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