Re: WITH AS vs subselect was: count (DISTINCT expression [ , ... ] ) and documentation

On Fri, Dec 26, 2008 at 07:13:48PM -0500, Tom Lane wrote:
> Ivan Sergio Borgonovo <mail(at)webthatworks(dot)it> writes:
> >>> David Fetter <david(at)fetter(dot)org> wrote:
> >>>> In 8.4, you'll be able to do:
>
> >>>> WITH d AS (
> >>>> SELECT DISTINCT c1, c2 FROM table1
> >>>> )
> >>>> SELECT count(*) FROM d;
>
> >>> Nice, but what will be the difference from
> >>> select count(*) from (select distinct c1, c2 from t);
> >>> ?
> >>> Optimisation?
>
> >> None especially.
>
> > So what would be the advantage compared to subselect?
>
> None, David just has WITH on the brain ;-)

LOL!

You're only saying that because it's true ;)

Cheers,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter
Skype: davidfetter XMPP: david(dot)fetter(at)gmail(dot)com

Remember to vote!
Consider donating to Postgres: http://www.postgresql.org/about/donate