>Not necessarily so. The source for the select may be anything - a result from a previous SQL, a XmlToCursor() cursor, a SPT cursor - and there's no way Fox could rely on any key there to be a key of any sort, specially when none of them (nor the regular tables) are required to have indexes of any kind. And it does have the requirement to work in all of those cases - so it has to compare all fields. It has done so since 2.0.

Thanks for the additional information

It's one of those clauses I never use.