// 返回符合条件记录的件数
$account_cnt = Student::model()->count("age=:age and sex=:sex ",array(
        ':age'=>trim($age),
        ':sex'=>trim($sex),
    ));


// 返回该条件下的记录是否存在
$criteria = new CDbCriteria;
$criteria->condition = "age=:age and sex=:sex and type in ('1','2')";
$criteria->params = array(':isp_id'=>yii::app()->user->getState('ispid'),
        ':age'=>trim($age),
        ':sex'=>trim($sex),
    );
$isExsit = Student::model()->exists($criteria);