title: Unknown column - multiple joins in CDbCriteria
body: <p>I'm trying to get data from multiple tables and I've ended with this error:
  SQL: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'p.firstname' in 'field list'</p>
  
  <pre><code>    $criteria = new CDbCriteria;
      $criteria-&gt;select = 'ohu_id, hash, p.firstname, p.surname, p.city, u.email AS Email';
      $criteria-&gt;join = 'LEFT JOIN `profiles` p ON  p.user_id = user_id';
      $criteria-&gt;join = 'LEFT JOIN users u ON user_id = u.id';
      $criteria-&gt;condition = 'offer_id = :oID';
      $criteria-&gt;params = array(':oID' =&gt; $_GET['id']);
  
      $model = MyModel::model()-&gt;findAll($criteria);
  </code></pre>
  
  <p>Anyone know what I'm doing wrong?
  Or is there better way to get related data?</p>