yii?删除约束

数据表category: category_id category_titlesubcategory:subcategory_id subcategory_category(与category_id关联)      在删除category表的数据时,要确保category_id在subcategory_category中不存在控制器: public function actiondelete($id)    {        if(yii::app()->request->ispostrequest)        {            $model=$this->loadmodel($id);            $results = category::getsubcategoryset($id);             //查找当前category_id是否在subcategory_category中存在                        //存在的话,就要提醒用户            //我这里是通过抛异常来提醒用户的,但我不想要错误编号的出现            //或者你们有更好的方法可以告诉我            if($results!=0){                throw new chttpexception(400,'this title is use on sub-category management');            }else{                $model = $this->loadmodel($id);                $model->category_status = 'd';                if ($model->validate()) {                    $model->save();                }                // $model->delete();                // if ajax request (triggered by deletion via admin grid view), we should not redirect the browser                if(!isset($_get['ajax']))                    $this->redirect(isset($_post['returnurl']) ? $_post['returnurl'] : array('admin'));            }        }

SiteController.phppublic function actionError()	{	    if($error=Yii::app()->errorHandler->error)	    {	    	if(Yii::app()->request->isAjaxRequest)	    		echo $error['message'];                        //去掉这个就不会显示错误信息    但错误编号还在   Error:400	    	else	        	$this->render('error', $error);	    }	}site视图下有 error.php 整个删掉都没影响