title: Mysql order by block several times
body: <p>I have a query that looks like this:</p>
  
  <blockquote>
    <p>SELECT t.realtimedatas_timestamp  FROM tr_realtimedatas as t ORDER BY t.realtimedatas_timestamp DESC LIMIT 1;</p>
  </blockquote>
  
  <p>And my table contains these columns</p>
  
  <blockquote>
    <p>id,name,serial_number,realtimedatas_timestamp,realtimedatas_created,realtimedata_updated</p>
  </blockquote>
  
  <p>when i call  <code>mysql --version</code> it give me :</p>
  
  <blockquote>
    <p>mysql  Ver 14.14 Distrib 5.5.53, for debian-linux-gnu (x86_64) using readline 6</p>
  </blockquote>
  
  <p>Everything works fine, but after i move to this new version of mysql  </p>
  
  <blockquote>
    <p>mysql  Ver 14.14 Distrib 5.6.36, for Linux (x86_64) using  EditLine wrapper</p>
  </blockquote>
  
  <p>The query blocked several times to get the last data inserted in the database ordered by  <code>realtimedatas_timestamp</code>,</p>
  
  <p>Is the problem with the mysql version or something else.
  what is the best query to get the data ordered by a feild.</p>