题解 | #SQL69：每日新登录用户数#
牛客每个人最近的登录日期(四)
http://www.nowcoder.com/practice/e524dc7450234395aa21c75303a42b0a
对于每个用户来说，只有他第一次登录的那天 他才是新用户
select
t.date,
sum(case when t.date=t.min_date then 1 else 0 end) as new
from (
select
date,
min(date) over(partition by user_id) as min_date
from login
) t
group by date
order by date
