Another couple of possible ways: Select groupfield,value >From tbl x1 Where number = (select max(number) from tbl x2 where x2.groupfield= x1.groupfield) Select groupfield,value >From tbl x1 Where (groupfield,number) in (select groupfield,max(number) from tbl group by groupfield) Which is quickest? Probably best to try out and see. -----Original Message----- From: pgsql-performance-owner@xxxxxxxxxxxxxx [mailto:pgsql-performance-owner@xxxxxxxxxxxxxx] On Behalf Of Kevin Grittner Sent: Tuesday, August 10, 2010 7:38 PM To: Matthew Wakeling; pgsql-performance@xxxxxxxxxxxxxx Subject: Re: Sorted group by Matthew Wakeling <matthew@xxxxxxxxxxx> wrote: > I'm trying to eke a little bit more performance out of an application In addition to the suggestion from Thomas Kellerer, it would be interesting to try the following and see how performance compares using real data. select group, value from tbl x where not exists (select * from tbl y where y.group = x.group and y.number > x.number); We have a lot of code using this general technique, and I'm curious whether there are big gains to be had by moving to the windowing functions. (I suspect there are.) -Kevin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.851 / Virus Database: 271.1.1/3061 - Release Date: 08/09/10 21:35:00 -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
