题解 | 有取消订单记录的司机平均评分_union

(select
    driver_id,
    round(avg(grade), 1) avg_grade
from
    tb_get_car_order
where
    grade is not null
    and driver_id in (
        select
            driver_id cl_driver
        from
            tb_get_car_order
        where
            grade is null
    )
group by
    driver_id
order by driver_id
)
union all
(
select
    "总体" ,
    round(avg(grade), 1) avg_grade
from
    tb_get_car_order
where
    grade is not null
    and driver_id in (
        select
            driver_id cl_driver
        from
            tb_get_car_order
        where
            grade is null
    )
)