题解 | #SQL71 牛客每个人最近的登录日期(六)#
牛客每个人最近的登录日期(六)
http://www.nowcoder.com/practice/572a027e52804c058e1f8b0c5e8a65b4
截止到某日期，用户累计通过的题目数量
关键点：累计-->某个日期及过去日期里的刷题通过数量的加和-->想到自连接判断日期大小
select
t1.name as u_n,
t2.date,
t2.ps_num
from user t1
right join (
select
p1.user_id,
p1.date,
sum(p2.number) as ps_num
from passing_number p1
left join passing_number p2
on p2.date<=p1.date
where p1.user_id = p2.user_id
group by p1.user_id,p1.date
)t2
on t1.id=t2.user_id
order by t2.date asc, t1.name asc
