Guys,

By replacing the union query with a temporary table you can get a further performance enhancement, this implies that a Constant scan is slower than a Table scan.

My results...

Beginning test run...1 NOT IN

Elapsed Time: 121543 ms

Beginning test run...2 <>

Elapsed Time: 132310 ms

Beginning test run...3 LEFT OUTER JOIN

Elapsed Time: 105760 ms

Beginning test run...4 NOT EXISTS (UNION)

Elapsed Time: 96250 ms

Beginning test run...5 NOT EXISTS (temp table)

Elapsed Time: 66633 ms

ta.

Nick