title: Use CActiveRecord to get the sum of a column
body: <p>1) Is there a way to get the sum of an integer column using CActiveRecord in Yii?</p>
  
  <p>Otherwise I will have to get the column data and sum it up on the server side.  </p>
  
  <p>2) I also assume getting the sum via one sql query is faster than getting the column of data and sum it up on the server with php.  If performance matters, should the mysql server be bothered to do such operation or just let the php server to take care of this.  </p>
  
  <p>Please kindly advice.</p>