Not sure how to bing this, so, I am asking here. I have Primary Key of three columns. If I only query against one of the column, will primary key be used?
Like for example,
Primary Key = OrderID, LineItemID.
And I just say, SELET * FROM Items WHERE OrderID = 0001, will this be fast? Or do I need to create a separate index? I kind of think the index with more columns is capable of being used when subset of columns are queried?