How to properly index a many-many association table?

Question

In a typical many-many arrangement like this...

Movies       Actors       Movies_Actors
------       ------       -------------
movie_ID     actor_ID     FK_movie_ID
         


        

Answer 1

In SQL Server, a composite index can be used for a single field search for the first column only. That means you should have an additional, one field index on FK_actor_id if there will be searches on that field without FK_Movie_id in the same query.