Re: Keeping top N records of a group

Alex Magnum <magnum11200(at)gmail(dot)com> wrote:

> Hi,
> i want to archive data and am looking for a query to replace a rather slow
> function i am currently using.
>
> The idea is that for every sym and doc_key I want to keep the records of the
> top 2 sources. Eg. in below table I want to archive 

sounds like a case for window-functions here (maybe row_number() or
rank()), please read that for the start:

http://stackoverflow.com/questions/7613785/postgresql-top-n-entries-per-item-in-same-table

Regards, Andreas Kretschmer
--
Andreas Kretschmer
http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services