>Dore,
>
>Is there more than one field in the origional tables? I don't think subqueries are optimizable, so in the first example all of table1 may need to be passed without an index, but in the second example you pulled a smaller file with just one field. The subquery in the second example would still not be optimizable, but there's far less to load and pass.

I believe that IN subqueries are optimizable, but a NOT IN is not.