sql primary key and index

Question

Say I have an ID row (int) in a database set as the primary key. If I query off the ID often do I also need to index it? Or does it being a primary key mean it\'s already in

Answer 1

Primary keys are always indexed by default.

You can define a primary key in SQL Server 2012 by using SQL Server Management Studio or Transact-SQL. Creating a primary key automatically creates a corresponding unique, clustered or nonclustered index.

http://technet.microsoft.com/en-us/library/ms189039.aspx