title: Does UNION ALL guarantee the order of the result set
body: <p>Can I be sure that the result set of the following script will always be sorted like this O-R-D-E-R ?</p>
  
  <pre><code>SELECT 'O'
  UNION ALL
  SELECT 'R'
  UNION ALL
  SELECT 'D'
  UNION ALL
  SELECT 'E'
  UNION ALL
  SELECT 'R'
  </code></pre>
  
  <p>Can it be proved to sometimes be in a different order?</p>