题解 | #有取消订单记录的司机平均评分#

不会with rollup的后果：

 select driver_id,
			   round(avg(case when grade is not null then grade end),1) as avg_grade
               from tb_get_car_order
               where driver_id in
			   (select driver_id from tb_get_car_order where grade is null and date_format(order_time,'%Y-%m') = '2021-10')
               group by driver_id 
		union
        (select '总体' as 总体,
				round(avg(case when grade is not null then grade end),1) as avg_grade
                from tb_get_car_order
                where driver_id in
                (select driver_id from tb_get_car_order where grade is null and date_format(order_time,'%Y-%m') = '2021-10'));