Yii CGridView.显示不相关表中的列

目前我有CGridView与列从几个连接表，但我也需要从其他表添加额外的列，我不能与第一个表连接，因为它们之间没有关系。

第二表assessment_rate:

id  title_id    rate    users_id    date_entry
0   2137        0       1           2013-08-28 08:43:54.000000
1   2139        1       1           2013-08-28 08:47:13.000000
2   2140        2       1           2013-08-28 08:57:44.000000
3   2141        3       1           2013-08-28 08:59:10.000000

我需要在CGridView中获得4个额外的列，从上面的表(值0,1,2,3)生成单选按钮(每列一个按钮)。

模型文件:

class form extends CActiveRecord {
public function init() {
    Yii::import('application.modules.admin.models.user');
    Yii::import('application.modules.admin.models.language');
}
public function tableName() {
    return 'ass_competence';
}
public function relations() {
    return array(
        'lan' => array(self::BELONGS_TO, 'language', 'title_id'),
        'lan_desc' => array(self::BELONGS_TO, 'language', 'description_title_id'),
        'use' => array(self::BELONGS_TO, 'user', 'users_id'),
        'rela' => array(self::BELONGS_TO, 'relation', array('id' => 'record_id')),
    );
}
public function attributeLabels() {
    return array(
        'lan.name_lt' => Yii::app()->reg->lang['title'],
        'use.username' => Yii::app()->reg->lang['user'],
        'lan_desc.name_lt' => Yii::app()->reg->lang['description'],
        'date_entry' => Yii::app()->reg->lang['date_entry'],
        'assessment' => Yii::app()->reg->lang['assessment'],
    );
}
public function search() {
    $criteria = new CDbCriteria;
    $criteria->with = array('use', 'lan', 'rela', 'lan_desc');
    $criteria->addCondition('rela.record_id IS NULL');
    $criteria->group = 't.id';
    $criteria->order = 't.id ASC';
    $criteria2 = new CDbCriteria;

    return new CActiveDataProvider($this, array(
        'criteria' => $criteria,
    ));
}
public static function model($className = __CLASS__) {
    return parent::model($className);
}
}

class FormController extends ControllerDefault {
public $model_name = 'Form';
public function beforeActionConfig() {

    $this->reg['title'] = Yii::app()->reg->lang['players'];
}
public function actionIndex() {
    $model = new form('search');
    $columns_top = array('' => 2,
        Yii::app()->reg->lang['assessment'] => 4,
    );
    $columns_main = array('lan.name_lt',
        'lan_desc.name_lt',
        'CountryName' => array(
            'header' => 'Country',
            'name' => 'Name',
            'value' => '1',
        ),
    );
    $dataProvider = $model->search();
    $this->render('index', array('model' => $model, 'dataProvider' => $dataProvider, 'columns_main' => $columns_main, 'columns_top' => $columns_top));
}
}

视图文件:

$this->widget('CGridViewPlus', array(
    'dataProvider' => $dataProvider,
    'addingHeaders' => array(
        $columns_top, // first header row
    ),
    'columns' => $columns_main //second header row
));