yii框架，绑定参数不工作

我有这部分代码，但它不会保存更改。你能告诉我：为什么？

        $var1 = $this->url_path."/";
        $var2 = $this->oldUrlPath."/";
        $var3 = $this->url_path."/%";
        $query = "UPDATE page SET url_path = REPLACE(url_path, :oldUrlPath, :url) WHERE          url_path LIKE :urlLike AND section_id = ".$this->section_id;
        $command=Yii::app()->db->createCommand($query);
        $command->bindParam(':url',$var1, PDO::PARAM_STR);
        $command->bindParam(':urlLike',$var3, PDO::PARAM_STR);
        $command->bindParam(':oldUrlPath',$var2, PDO::PARAM_STR);
        if(!$command->query()) throw new CDbException(tb('Cannot update children pages'));