tp5 where查询数据库中的没某个字段是否包含某个值

//TP5 find_in_set用法

$where['parent_store_id'] = $this->parent_store_id;
            $where['status'] = 'up';
            $where['type'] = 'normal';
            $where['deletetime'] = NULL;
            $data[$k]['children'] = db('shopro_goods')
            ->where($where)
            ->where('find_in_set(8,category_ids)')
            ->order('weigh asc')->select();