sum + 窗口函数 lag() over
牛客每个人最近的登录日期(四)
http://www.nowcoder.com/practice/e524dc7450234395aa21c75303a42b0a
select user_id, date,lag(date, 1) over (partition by user_id order by date) as lastdate from login;
select `date`, sum(case when lastdate is null then 1 else 0 end) as new
from
(select user_id, `date`,lag(`date`, 1) over (partition by user_id order by `date`) as lastdate from login)
as t
group by t.`date`;
顺丰集团工作强度 371人发布