Re: SQL Newbie

On Fri, Aug 12, 2005 at 18:57:34 +0100,
Nick Stone <nick(at)harelane(dot)com> wrote:
> Hope this helps
>
> SELECT
> *
> FROM
> speed_history as outside etc..
> WHERE
> (speed = (
> SELECT
> speed
> FROM
> speed_history as inside etc..
> WHERE
> (outside.interface = inside.interface)
> LIMIT 1
> ORDER BY
> speed DESC
> )
> )
>
> Hopefully you get the idea - basically it's a corelated sub-query - very
> useful
>

Note that you want to order by interface DESC, speed DESC in the subselect
and have an index on (interface, speed) for this to really be efficient.
I think 8.1 might be smart enough to use an index on (interface, speed)
in the above case, but currently released versions won't.