题解 | #有取消订单记录的司机平均评分#

    SELECT coalesce(driver_id,'总体'),round(sum(grade)/count(grade),1) avg_grade
    FROM tb_get_car_order t2
    left JOIN tb_get_car_record t1 USING(order_id)
    where driver_id in (SELECT driver_id
    FROM tb_get_car_order t2
    left JOIN tb_get_car_record t1 USING(order_id)
    where start_time is null) 
    group by driver_id with rollup