PHP YII框架学习 按条件查询显示在YII自带的CGridView上

 我有2个表 ：url_info ; category
url_info 字段： id，cid ,title
category字段：id ,name
其中url_info.cid=category.id
目的：就是关联2个表查询出 这样的结构  url_info.id  category.name  title

其中url_info model中的关系如下写：
/**
* @return array relational rules.
*/
public function relations()
{
// NOTE: you may need to adjust the relation name and the related
// class name for the relations automatically generated below.
return array(
'category'=>array(self::BELONGS_TO, 'category', 'cid'),
);
}

控制层：
/**
* Manages all models.
*/
public function actionAdmin()
{
$dataProvider=new CActiveDataProvider('url_info', array(
'criteria'=>array(
'condition'=>'cid=category.id',
'with'=>array('category'),
'order'=>'cid desc',
),
'pagination'=>array(
'pageSize'=>self::PAGE_SIZE,
),
));

$this->render('admin',array(
'dataProvider'=>$dataProvider,
));
}

显示层：
$this->widget('zii.widgets.grid.CGridView', array(
'dataProvider'=>$dataProvider,
'columns'=>array(
'id',
'category.name',
'title',
array(
'class'=>'CButtonColumn',
),
),

sql 语句：
mysql> select url_info.id,cid,category_name from url_info,category where url_inf
o.cid=category.id;