title: Combing CASE WHEN with NVL() and GROUP BY
body: <p>I do a <code>CASE WHEN</code> in my SELECT to convert any null into <code>'None'</code>. I also want to take a specific non-null value (e.g. <code>'X'</code>) and treat this the same as the null values (e.g. make them all <code>'None'</code>).</p>
  
  <p>I do something like this:</p>
  
  <pre><code>SELECT
  CASE WHEN Val = 'X' THEN 'None' ELSE NVL(Val, 'None') END ValCol
  FROM tbl
  GROUP BY Val
  </code></pre>
  
  <p>What I end up with is two rows of 'None'; in essence the two 'None' values are being treated separately. </p>
  
  <p>How do I combine them?</p>