WayneS (7/22/2010)
I would agree that Unique, filtered and included indexes are a sub-type of the clustered (for Unique) or non-clustered index types. However, according to the latest Microsoft documentation, they are a type of index. I'm not going to base a QotD off of what I believe it should be without any documentation to back me up.You might want to take a look at SQL 2008 (R1) BOL for index types at http://msdn.microsoft.com/en-us/library/ms175049.aspx%28sql.100%29 - here they list 9 (they included Indexed Views). Since an Indexed View is a type of a view, physically manifested by having a clustered index and optionally having non-clustered indexes, I believe that it is correct that it was removed from this list.
I don't subscribe to the logic that if it's on BOL, it must be true. If you want to include sub index types, you could include Ascending and Descending. The list could go on and on.