"hubert depesz lubaczewski" <depesz@xxxxxxxxxx> writes: > On Wed, Sep 05, 2007 at 12:30:21PM +0100, Gregory Stark wrote: >> SELECT DISTINCT ON (id) id, the_date AS min_date FROM my_table ORDER BY id, the_date ASC >> SELECT DISTINCT ON (id) id, the_date AS max_date FROM my_table ORDER BY id, the_date DESC >> I think the first of these can actually use your index but the latter can't >> unless you create one for it specifically (which is not so easy -- it'll be >> easier in 8.3 though). Worse, I'm not really sure it'll be any faster than the >> query you already have. > > it's easy to fix the second query (fix to use index) - just change order > by to: > order by id desc, the_date desc. Cute. I didn't think of that, thanks -- Gregory Stark EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 7: You can help support the PostgreSQL project by donating at http://www.postgresql.org/about/donate
