title: Finding unmatched records with SQL
body: <p>I'm trying write a query to find records which don't have a matching record in another table.</p>
  
  <p>For example, I have a two tables whose structures looks something like this:  </p>
  
  <pre>
  Table1
      State | Product | Distributor | other fields
      CA    | P1      |  A          | xxxx
      OR    | P1      |  A          | xxxx
      OR    | P1      |  B          | xxxx
      OR    | P1      |  X          | xxxx
      WA    | P1      |  X          | xxxx
      VA    | P2      |  A          | xxxx
  
  Table2
      State | Product | Version | other fields
      CA    | P1      |  1.0    | xxxx
      OR    | P1      |  1.5    | xxxx
      WA    | P1      |  1.0    | xxxx
      VA    | P2      |  1.2    | xxxx
  </pre>
  
  <p>(State/Product/Distributor together form the key for Table1. State/Product is the key for Table2)  </p>
  
  <p>I want to find all the State/Product/Version combinations which are Not using distributor X.  (So the result in this example is CA-P1-1.0, and VA-P2-1.2.)  </p>
  
  <p>Any suggestions on a query to do this?</p>