On Tue, Jan 09, 2007 at 05:07:03PM -0800, Brian Herlihy wrote:
> Actually, as I recently discovered, GROUP BY is faster than DISTINCT. It's
> just due to how they are implemented, so don't go looking for any deep
> reason :) The thread "GROUP BY vs DISTINCT" from 2006-12-20 discusses it.
> DISTINCT sorts the results to find the unique rows, but GROUP BY uses a
> hash.
Actually, GROUP BY _can_ use a sort too, it's just that a hash is usually
faster.
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