>I am using a concatenated key in my query. While I can test what you mentioned,
it would be slower than what I mentioned in my original post. (Speed test has been done here on the UniversalThread.)

Strange, SYS(3054) message is ?

>The question remains, why does it happen for one table and not another when there are NO indexes applied to any of the tables?

Because VFP , if it can, use index or build temp index.

>Why does it work in VFP8 and not in VFP7 Service Pack 1?

A bug fixed ?

>Strange how you can get an Invalid Key Length error when there are no indexes on the tables!

Because VFP can do IN,EXISTS,... subquery only if it can do a seek, if a index not exists
VFP build a temp index ( see SYS(3054,11) message ).

Fabio