title: Remove "Using filesort" for simple MySQL query
body: <p>I am trying to remove filesort from a simple MySQL query.</p>
  
  <p>The table has the column <code>active</code> which is either 0 or 1 and has a column <code>season_average</code> which is an integer, and no joins.</p>
  
  <p>My select statement is as follows:</p>
  
  <pre><code>SELECT 
  *
  FROM `group` WHERE active=1 
  ORDER BY season_average DESC
  </code></pre>
  
  <p>I have tried an index on <code>active</code>, on <code>season_average</code>, and multiple columns on <code>(active, season_average)</code> and <code>(season_average, active)</code> None of which solve the issue.</p>
  
  <p>This SQL Fiddle shows the problem I am having: <a href="http://sqlfiddle.com/#!9/77861/2" rel="nofollow">http://sqlfiddle.com/#!9/77861/2</a></p>
  
  <p>Is there a way to get around this problem?</p>