In response to Vratislav Benes :
> but when I try make a condition by join table, the query plan is not optimal:
>
>
> select period_id from periods where y=2009 and w=14;
> period_id
> -----------
> 704
> (1 row)
>
>
> explain select sum(s_pcs),sum(s_val)
> from data d inner join periods p on d.period_id=p.period_id
> where p.y=2009 and p.w=14;
How about
select sum(s_pcs),sum(s_val)
from data d inner join periods p on d.period_id=p.period_id
where p.y=2009 and p.w=14
and p.period_id in (select period_id from periods where y=2009 and w=14);
Untested.
Andreas
--
Andreas Kretschmer
Kontakt: Heynitz: 035242/47150, D1: 0160/7141639 (mehr: -> Header)