title: Using ORDER BY in $wpdb
body: <p>If I query the database using this code, I get an array of 4 objects as expected.</p>
  
  <pre><code>global $wpdb;
  $rows = $wpdb-&gt;get_results("SELECT * FROM ppm_playlists");
  var_dump($rows); die();
  </code></pre>
  
  <p>But if I query using this, I get an empty array.</p>
  
  <pre><code>global $wpdb;
  $rows = $wpdb-&gt;get_results("SELECT * FROM ppm_playlists ORDER BY sort-order ASC");
  var_dump($rows); die();
  </code></pre>
  
  <p>Is there a "trick" to using "ORDER BY" in the database class that I am missing in the documentation?</p>
  
  <p>Thanks in advance.</p>