On Thu, Aug 28, 2003 at 19:50:38 -0700, Ken Geis <[EMAIL PROTECTED]> wrote: > Bruno Wolff III wrote: > >On Thu, Aug 28, 2003 at 17:10:31 -0700, > > Ken Geis <[EMAIL PROTECTED]> wrote: > > > >>The query I want to run is > >> > >>select stock_id, min(price_date) from day_ends group by stock_id; > > > >The fast way to do this is: > > > >select distinct on (stock_id) stock_id, price_date > > order by stock_id, price_date; > > Not according to the optimizer! Plus, this is not guaranteed to return > the correct results.
For it to be fast you need an index on (stock_id, price_date) so that you can use an index scan. The answers are guarenteed to be correct. See: http://developer.postgresql.org/docs/postgres/sql-select.html#SQL-DISTINCT ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
