title: MySQL update is running slow
body: <p>The following query:</p>
  
  <pre><code> UPDATE `zydushr`.`performance`  AS a1 , `zydusquiz`.`performance` AS a2 
   SET a1.`Sales` = a2.`AchievementHQ` WHERE a1.`EmpNo` = a2.`EmpNo` 
   AND a1.`Month` = a2.`Month` AND a1.`Year` = a2.`Year` ; 
  </code></pre>
  
  <p>is running very slowly. How can I speed it up?</p>
  
  <p>Note: i have already created the indexes.</p>