题解 | #牛客每个人最近的登录日期(四)#

-- 窗口 函数实现方法
select
    t1.date,
    sum(case when t1.rk = 1 then 1 else 0 end) as new
from
    (
        select
            user_id,
            date,
            row_number() over (
                partition by
                    user_id
                order by
                    date
            ) as rk
        from
            login
        group by
            user_id,
            date
    ) as t1
group by date;