george young <gry(at)ll(dot)mit(dot)edu> writes:
> This schema seemed logical at the outset, but the most common query is:
> select m.machine_name, m.text, ml.status, ml.date
> from machine m, machine_log ml
> where m.machine_name=ml.machine_name and ml.date=(select max(date)from
> machine_log where machine_name=ml.machine_name);
You can do this a lot better with SELECT DISTINCT ON --- see the "weather
report" example in the SELECT reference page. Given a suitable index
it should even be pretty quick.
regards, tom lane