题解 | #牛客每个人最近的登录日期(四)#

题目要求：统计用户登录的次数 采用 sum (case when then ,when then ,else) 思路：用户每登录一次，则次数+1,；否则次数不变；以日期为分组对象

select distinct date ,
sum(case when (user_id,date) in (select user_id,min(date) from login group by user_id) then 1
    else 0 
    end)
    from login 
    group by date 
    order by date