title: mysql - Find duplicate users with firstname/lastname swapped
body: <p>I need to find users that have been inserted twice in a table, but with their first name &amp; last name swapped.</p>
  
  <p>e.g. Bob Smith is in the database as </p>
  
  <pre><code>firstname:Bob 
  lastname:Smith
  &amp;
  firstname:Smith
  lastname:Bob
  </code></pre>
  
  <p>What's the best query to find those users?</p>
  
  <p>The server runs mysql. </p>