题解 | #各城市最大同时等车人数#

from
(select city,order_id,event_time,end_time
from tb_get_car_record
WHERE DATE(event_time) BETWEEN '2021-10-1'AND '2021-10-31')t1
left join 
(select order_id,order_time,start_time,finish_time
from tb_get_car_order
)t2
on t1.order_id=t2.order_id)

select city,max(total_wait) total_city_wait
from
(select city,sum(num) over (partition by city,date(dates) order by dates,num desc) total_wait
from
(select city,event_time dates,1 as num from a 
union all
select city,ifnull(start_time,finish_time) dates,-1 as num from a 
union all
select city,end_time dates,-1 as num from a where order_id is null)t1)t2
group by city
order by total_city_wait ,city asc
#当初定的职场小目标实现了多少#