title: Adding an identity to an existing column
body: <p>I need to change the primary key of a table to an identity column, and there's already a number of rows in table. </p>
  
  <p>I've got a script to clean up the IDs to ensure they're sequential starting at 1, works fine on my test database. </p>
  
  <p>What's the SQL command to alter the column to have an identity property?</p>