On Wed, Jan 26, 2005 at 23:12:25 +0100,
PFC <lists@boutiquenumerique.com> 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.
