title: drupal 7 $query->where and DATE_FORMAT not recognized
body: <p>I have implement a function views_query_alter.
  I want to add a where clause. 
  I try with : $query->add_where(0, "DATE_FORMAT(myfieldname, '%Y-%m-%d')", "DATE_FORMAT(now(), '%Y-%m-%d')", '>');</p>
  
  <p>I also try with condition.
  The result printed sql is the same from both cases and is DATE_FORMATmyfieldnameYmd. Is there any way to escaped a DATE_FORMAT or anything to succesfully recognized DATE_FORMAT function into where clause?</p>
  
  <p>Thank you in advance</p>