题解 | #各城市最大同时等车人数#

select city,max(wait_uv) max_wait_uv
from
(
select city , sum(cnt)over(partition by city order by dt , cnt desc)wait_uv
from
(
select city,timestamp(event_time) dt, +1 cnt
from tb_get_car_record
where date_format(event_time,"%Y%m")="202110"
union all
select city,timestamp(ifnull(start_time,finish_time)) dt, -1 cnt
from tb_get_car_record left join tb_get_car_order using(order_id)
where date_format(event_time,"%Y%m") = "202110"
)t1
)t2
group by city
order by max_wait_uv,city