题解 | #有取消订单记录的司机平均评分#

#小白好理解的写法
with tiaojian as (
select 
driver_id
from tb_get_car_order            //求出有取消记录的司机
where
start_time is null
and
date_format(order_time,"%Y%m")=202110
)


select 
ifnull(
tr.driver_id,"总体"),
round(
avg(grade),1) as avg_grade  //把有取消记录的司机和总表连接，求出平均值，利用group by with rollup 一步到位
from tiaojian t inner join tb_get_car_order tr 
on tr.driver_id=t.t.driver_id
group by tr.driver_id with rollup