title: Maintain sql order in mysql after group
body: <p>I have next sql</p>
  
  <pre><code>select site_id,count from tags where match (tag) against ('statistici' in boolean mode) ORDER BY count DESC;
  
  +---------+-------+
  | site_id | count |
  +---------+-------+
  |       9 |  1300 |
  |      13 |  1200 |
  |       9 |  1100 |
  |      13 |  1000 |
  |       9 |   900 |
  |      13 |   800 |
  |      13 |   800 |
  +---------+-------+
  </code></pre>
  
  <p>What i need is to get distinct site_id.
  But when i use a group by statement the order by count is not kept</p>
  
  <pre><code>select site_id,count from tags where match (tag) against ('statistici' in boolean mode) GROUP by site_id ORDER BY count DESC;
  
  +---------+-------+
  | site_id | count |
  +---------+-------+
  |      13 |  1000 |
  |       9 |   900 |
  +---------+-------+
  </code></pre>
  
  <p>What should i do ?</p>