title: Is the Sql Server Unique Key also an Index?
body: <p>I've got a column in a table (eg. UserName) which I want to make sure is unique. So I create a unique key for that column and call it IX_Users_UserName.</p>
  
  <p>Now, if I do lots of searching for users based on their username I want to make sure there is an index for that field.</p>
  
  <p>Do I need to create a separate index, or is the unique key also considered an index, just like the primary key is a clustered unique key?</p>