title: SQL DELETE STATEMENT explanation
body: <p>This request works:</p>
  
  <p>There are two successive FROMs.
  When I delete the first one, it doesn't work why?</p>
  
  <pre><code>DELETE FROM TableA
  FROM TableA dim
  LEFT OUTER JOIN (
      SELECT DISTINCT ColA
      FROM TableB
      UNION ALL
      SELECT DISTINCT ColA
      FROM tableC
  
  ) A ON A.ColA= dim.ColA
  WHERE A.ColA IS NULL
  </code></pre>
  
  <p><strong>EDIT</strong> 
  This one doesn't work which I was supposing was the correct one:</p>
  
  <pre><code> DELETE 
      FROM TableA dim
      LEFT OUTER JOIN (
          SELECT DISTINCT ColA
          FROM TableB
          UNION ALL
          SELECT DISTINCT ColA
          FROM tableC
  
      ) A ON A.ColA= dim.ColA
      WHERE A.ColA IS NULL
  </code></pre>
  
  <p>Thanks</p>