Re: How to handle a group query

Nigel Metheringham <Nigel(dot)Metheringham(at)dev(dot)intechnology(dot)co(dot)uk> writes:
> What I am trying to do is get a set of rows out of a table based on a
> set of grouping constraints. A simplified form of the table I am using
> is:-
> CREATE TABLE grouptest (
> rowid serial PRIMARY KEY,
> grouping integer,
> tstval integer,
> other character varying);

> I want to get out rows of data where tstval is at a minimum value for
> each set GROUPed by grouping. If there is more than one row with the
> same minimal value for tstval then I want any of those rows (but the
> data for a row must be consistent).

If you don't mind using a Postgres-specific construct, SELECT DISTINCT ON
works nicely for this. See the "weather reports" example in the SELECT
reference page.

regards, tom lane