title: 'IF' in 'SELECT' statement - choose output value based on column values
body: <pre><code>SELECT id, amount FROM report
  </code></pre>
  
  <p>I need <code>amount</code> to be <code>amount</code> if <code>report.type='P'</code> and <code>-amount</code> if <code>report.type='N'</code>. How do I add this to the above query?</p>