title: Eliminate group of NULLs from result set
body: <p>I have a query that returns a result set similar to the one below:</p>
  
  <pre><code>   Quarter  | Count
     -------  | -----
  1   Q2 2009 | NULL
  2   Q2 2009 | NULL
  3   Q2 2009 | NULL
  4   Q3 2009 | 26
  5   Q3 2009 | 27
  6   Q3 2009 | NULL
  </code></pre>
  
  <p>I don't want rows 1-3, because their combined Quarter-Count is NULL.  But I do want rows 3-6 because at least one Count from the same Quarter is not NULL.</p>
  
  <p>How do I come from the result set above to this one:</p>
  
  <pre><code>   Quarter  | Count
     -------  | -----
  1   Q3 2009 | 26
  2   Q3 2009 | 27
  3   Q3 2009 | NULL
  </code></pre>
  
  <p>Thanks.</p>