title: SQL Partial primary key, composite key
body: <p>In the author/title entity the two "primary" keys should act together as a primary key , how can i do that in sql. Do i need to create a new key that hold those values? I know you're not allowed two have two primary keys in a entity but i didnt know how to write that they were compiste key/ partial primary keys. Im using sql server 2008</p>
  
  <p>Here's the link to the er diagram  ( <a href="http://img69.imageshack.us/img69/3048/68810818.png" rel="nofollow noreferrer">http://img69.imageshack.us/img69/3048/68810818.png</a> )</p>
  
  <p><img src="https://i.stack.imgur.com/VEE7V.png" alt="enter image description here"></p>