title: How can I order entries in a UNION without ORDER BY?
body: <p>How can I be sure that my result set will have <code>a</code> first and <code>b</code> second? It would help me to solve a tricky ordering problem.</p>
  
  <p>Here is a simplified example of what I'm doing:</p>
  
  <pre><code>SELECT a FROM A LIMIT 1 
  UNION 
  SELECT b FROM B LIMIT 1;
  </code></pre>