title: Adding column alias values used in case statement
body: <p>How can I sum the total of these column aliases when used in a case statement?</p>
  
  <pre><code>SELECT 
      (CASE WHEN TYPE = 'FEES' THEN AMOUNT END) AS Fees, 
      (CASE WHEN TYPE = 'PENALTY' THEN AMOUNT END) AS Penalty, 
      (CASE WHEN TYPE = 'INTEREST' THEN AMOUNT END) AS Interest, 
      SUM(Fees + Penalty + Interest) AS Total
  FROM MyTable
  </code></pre>
  
  <p>Note: There are more types than just the 3 summed, so <code>sum(Amount)</code> doesn't give the required result.</p>