title: $criteria->select in yii
body: <p>Is it possible to do the following in yii</p>
  
  <pre><code>$criteria=new CDbCriteria;
  $criteria-&gt;select='avg(rate) as avgRate,rate';
  </code></pre>
  
  <p>I executed the following code but its returning the value for the column "rate" but not "avgRate"
  I know this could be done by createcommand but I want to use CDbCriteria.</p>