title: How to use ORDER BY to place last the row when a column IS NOT empty string?
body: <p>I want to place last if a column (lets say 'answer') is not empty string.</p>
  <p>My base query:</p>
  <pre><code>SELECT messages.id
       , users.username
       , messages.answer 
    FROM MESSAGES 
    JOIN users 
      ON messages.user_id = users.id 
   ORDER 
      BY ?
  &quot;;
  </code></pre>
  <p>How to use ORDER BY to place NON EMPTY users.answer to the bottom?</p>
  <p>(It is like a ticket system so answered tickets should be last)</p>