title: SQL NOT IN () statement not working
body: <p>I am working with medical data and have a list of claim numbers. Those claim numbers have multiple revenue codes associated with each claim.  </p>
  
  <p>I am attempting to eliminate any claims that have a <code>REVENUE_CD</code> of 450.  </p>
  
  <p>The result however, still includes claims with that revenue code.  It appears to be returning claims that have the 450 along with other codes.  I need it to look at all the Revenue codes and eliminate claims that have 450 as any of the multiple codes.</p>
  
  <pre><code>SELECT claim_num
  FROM claims c
  WHERE revenue_cd NOT IN ('0450')
  </code></pre>
  
  <p><strong>RESULTS:</strong></p>
  
  <pre><code>ICN_NUM REVENUE_CD
  1   1335    0352
  2   1335    0300
  3   1335    0252
  4   1335    0306
  5   1335    0324
  6   1335    0272
  7   1335    0762
  8   1335    0305
  9   1335    0450
  10  1335    0637
  </code></pre>
  
  <p>Any help is greatly appreciated.</p>