Let’s discuss example relationship given on following URL

http://www.yiiframework.com/doc/guide/1.1/en/database.arr

If you want to be able to filter results in grid using Posts’ author name then modify the search function of  Post model to similar to the one given below.

public function search()
	{
		$criteria=new CDbCriteria;

		$criteria->compare('id',$this->id);

		if(!intval($this->author_id) && is_string($this->author_id) && strlen($this->author_id) > 0) {
			$criteria->with[]='user';
		  	$criteria->addSearchCondition("user.name",$this->author_id,true);
		}else{
			$criteria->compare('author_id',$this->author_id);
		}

		return new CActiveDataProvider(get_class($this), array(
			'criteria'=>$criteria,
			'pagination' => array(
				'pageSize'=>Yii::app()->params['defaultPageSize']
			)
		));
	}