I know I'm going to catch hell for suggesting using the deleted mark but this will work fast.

DELETE FROM table1 WHERE keyfield IN (SELECT keyfield FROM table2)
SELECT * FROM table1 WHERE !DELETED()

>I have some very large tables from which I have to get records NOT IN other very large tables. Code like this:
>
>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.
>
>Any ideas for something faster?