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From: A. Kretschmer <andreas.kretschmer@schollglas.com>
To: pgsql-sql@postgresql.org
Subject: Re: Ask About SQL
Date: Wed, 19 Aug 2009 12:46:48 +0200
Message-ID: <20090819104648.GA11859@a-kretschmer.de> (raw)
In-Reply-To: <1703cd180908190317p3b1c4140hc9cbe41331c0725e@mail.gmail.com>
References: <1703cd180908190317p3b1c4140hc9cbe41331c0725e@mail.gmail.com>

In response to Otniel Michael :
> Hi All.
> 
> Can help to create sql queries for this data :
> 
> tabel A
> field1, field2, field3
> x1,     y1,     5
> x1,     y2,     1
> x2,     y1,     2
> x2,     y3,     4
> x1,     y3,     4
> 
> I want to get 2 record with the max value at field3 for each kombination of
> field1 :
> 
> tabel B
> field1, field2, field3
> x1,     y1,     5
> x1,     y3,     4
> x2,     y3,     4
> x2,     y1,     2
> 
> Anyone have an ideas?

Works since 8.4:

test=*# select * from table_a ;
 field1 | field2 | field3
--------+--------+--------
 x1     | y1     |      5
 x1     | y2     |      1
 x2     | y1     |      2
 x2     | y3     |      4
 x1     | y3     |      4
(5 rows)

test=*# select field1, field2, field3 from (select field1, field2,
field3, row_number() over(partition by field1 order by field3 desc) from
table_a order by field1, field3) foo where row_number < 3 order by
field1, field2;
 field1 | field2 | field3
--------+--------+--------
 x1     | y1     |      5
 x1     | y3     |      4
 x2     | y1     |      2
 x2     | y3     |      4
(4 rows)


Regards, Andreas
-- 
Andreas Kretschmer
Kontakt:  Heynitz: 035242/47150,   D1: 0160/7141639 (mehr: -> Header)
GnuPG-ID:   0x3FFF606C, privat 0x7F4584DA   http://wwwkeys.de.pgp.net



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