modelName::model() -> find()　　　 //找出的是一个对象
modelName::model() -> findALL()　　//找出的是一个对象集合的数组

$criteria = new CDbCriteria;
$criteria->select = 'username,id,email';
$criteria->order = 'id DESC';
$users = modelName::model()->findAll( $criteria );

$users = modelName::model()->findAll(array(
  'select' =>array('username','id','email'),
  'order' => 'id DESC', 
));

$user = modelName::model()->find(array(
  'select' =>array('username','id','email'),
  'order' => 'id DESC',
  'condition' => 'id='.$id,
));

$users = $this->user->find(array(
  'select'=>array('id','username','email'),
  'order' => 'id DESC',
  'condition' => 'state=:state AND id=:id',
  'params' => array(':state'=>'1',':id' => '2'),
));