What are hypothetical indexes?

Question

Does anybody know what hypothetical indexes are used for in sql server 2000? I have a table with 15+ such indexes, but have no idea what they were created for. Can they slow down deletes/inserts?

Answer 1

hypothetical indexes are usually created when you run index tuning wizard, and are suggestions, under normal circumstances they will be removed if the wizard runs OK.

If some are left around they can cause some issues, see this link for ways to remove them.