CI框架 如何进行两个表同时进行删除数据？？？求高手 达人！！

public function delRelease($where){
$this->db->select('p1.*,p2.*');
$this->db->from("comment as p1");
$this->db->join('release as p2','p1.release_id = p2.release_id','left');
$this->db->where($where);
return $this->db->delete();
}
阵亡。。