title: Triggered update on mysql runs second time
body: <pre><code>BEGIN 
  SET new.Diff = DATEDIFF(new.RepairDate,new.FaultyDate);
  UPDATE po
  INNER JOIN xt ON po.SerialNumber = new.SerialNumber SET po.Edate = ADDDATE(po.Edate, new.Diff)
  WHERE po.SerialNumber = new.SerialNumber;
  END
  </code></pre>
  
  <p>This is my trigger statement. 
  I want to add to Edate the integer resulted using by datediff. 
  My only issue is that if I insert a test entry into the <code>xt</code> table to test this trigger nothing happens. 
  If I insert the same test entry second time it works as it should have in the first try. 
  After the second try everything works fine for that entry. 
  Where am I doing wrong? 
  please excuse me if it's a dumb question because I'm a newbie with mysql</p>
  
  <p>Sorry for my bad english and thank you in advance!</p>