题解 | #各城市最大同时等车人数#
各城市最大同时等车人数
http://www.nowcoder.com/practice/f301eccab83c42ab8dab80f28a1eef98
select city,max(截止目前等车人数) as 最大值 from
(select city,
(sum(标识) over(partition by city order by event_time,标识 desc)) as 截止目前等车人数
from
((select uid,
city,
event_time,
1 as 标识
from
tb_get_car_record where date_format(event_time,'%Y-%m') = '2021-10')
UNION
(select tb_get_car_order.uid,city,start_time,-1 as 标识
from
tb_get_car_order join tb_get_car_record on tb_get_car_order.uid = tb_get_car_record.uid
where date_format(event_time,'%Y-%m') = '2021-10')) a) b
group by city
order by 最大值,city;