Re: index usage in joins q'n

On Sat, Nov 03, 2007 at 11:42:39AM +0400, rihad wrote:
> Does this mean that a condition like "WHERE ... [AND] lhs.a=rhs.b [AND]
> ..." where rhs.b is already unique-indexed, also requires (non-unique)
> index on lhs.a for maximal join speed? Otherwise why would they want to
> say that?

No, as long as one of the two columns is indexed it can help. An index
on both might help if you need a lot of rows but it's a bit hard to
construct a situation where it'd be obvious.

Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Those who make peaceful revolution impossible will make violent revolution inevitable.
> -- John F Kennedy