title: GROUP_CONCAT(DISTINCT xxx) reverse the order of the concatened values
body: <p>I have some trouble with my sql request, when i compare thoses two GROUP_CONTACT,
  results seems to be reverse. I tried to put an order statement into the group_concat but with no success.</p>
  <p>How can i get the same result between GROUP_CONCAT without DISTINCT statement and GROUP_CONCAT with DISTINCT statement.</p>
  <pre><code>SELECT GROUP_CONCAT(a.artiste_nom SEPARATOR '|') as 'std', GROUP_CONCAT(DISTINCT a.artiste_nom SEPARATOR '|') as 'std1'
  FROM produit p
  LEFT JOIN produit_artiste pa ON pa.produit_id = p.produit_id 
  LEFT JOIN artiste a ON pa.artiste_id = a.artiste_id
  WHERE pa.produit_id = p.produit_id
  GROUP BY p.produit_id 
  HAVING std &lt;&gt; std1
  </code></pre>
  <p>while using GROUP_CONCAT(DISTINCT a.artiste_nom ORDER BY a.artiste_nom ASC SEPARATOR '|') made no difference at all</p>
  <p>GROUP_CONCAT(DISTINCT a.artiste_nom ORDER BY a.artiste_nom DESC SEPARATOR '|') had changed the way the table is parse.</p>