Last month, I told you about changes to the query optimizer's behavior in SQL Server 2000 and 7.0 and the huge increase in the optimizer's complexity. The optimizer can evaluate so many more possible plans than in previous releases that there's no guarantee that the optimizer will always find the best plan; the optimizer's goal is to find a plan that's "good enough." This month, let's look at a couple of the new query-processing techniques that the optimizer can include in a query plan.