Bruce,

>select * from table1;
where keyfield NOT IN;
(select keyfield from table2)

>is not optimizable, and is extremely slow (about 15 minutes or more) for each query. I have tried a SCAN/SEEK, but it is at least as slow or worse, since you're looking for unique keys that don't exist, and therefore must hit every record.

Try using a left join.

select * from table1 left join table2 on table1.keyfield = table2.keyfield
where isnull(table2.keyfield)

This will return only the records from table1 where there is no match in table2.

Cheers
Steve Lea