select ifnull(driver_id,"总体")as driver_id,round(avg(grade),1)'平均评分' from tb_get_car_order where driver_id in (select driver_id from tb_get_car_order where date_format(order_time,'%Y-%m')='2021-10'and isnull(fare))and not isnull(grade) group by driver_id  with rollup;

有点不理解ifnull(driver_id,"总体")as driver_id 和最后面的with rollup的用法！！！！！！！！！！