title: unique key based on 2 columns in SQl Server 2008?
body: <p>is it posible to have SQL Server to have a unique key based on 2 columns?  </p>
  
  <p>I can have duplicates in both columns but not at the same time:</p>
  
  <pre><code>MfgID  :   CustNum   
  1      :     Cust01   
  1      :     Cust02  
  2      :     Cust02  
  1      :     Cust03  
  3      :     Cust03  
  3      :     Cust04  
  1      :     Cust02
  </code></pre>
  
  <p>In the example above all of these would be fine EXCEPT the last row.  I'd like SQL Server to kck out an error on this for me.</p>