title: Is an index (1 column) on a primary key (> 1 column) useful? (SQL)
body: <p>I have a table with more than 40k rows and a primary key consisting of 2 columns on this table.</p>
  
  <p>Could a seperate nonclustered (NOT unique!) index on ONE of these primary key columns speed up queries on THIS column (without using the other PK columns)? Or would SQL Server use the primary key in an equally efficient manner for accessing only one column of the primary key?</p>
  
  <p>I know a primary key is a unique index but that has nothing to do with the question, I'm just concerned about the primary key spanning multiple columns as opposed to one when accessing data just from one of the PK columns..</p>