On Wed, Jan 26, 2005 at 23:12:25 +0100, PFC <lists@xxxxxxxxxxxxxxxxxxxxx> wrote: > > How do you do a self-join on a subselect ? > > like > SELECT a.x+b.x FROM (subselect) a, (subselect) b WHERE a.id = b.id+10 > > but without performing the subselect twice > ..................................? You have to write the subselect twice if you want to match up different rows. In some cases it might be worth making a copy in a temp table. For simple subselects where there is an index on id, leaving it as is should work fine. ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend
