用户次留问题

select user_login_date
    ,retained_1_uv / retained_uv as retained_1_ctr --次留率
    ,retained_3_uv / retained_uv as retained_1_ctr --3日留存率
    ,retained_7_uv / retained_uv as retained_1_ctr --7日留存率
from 
(
    select user_login_date --登录日期
        ,count(distinct b.userid) as retained_uv --当日活跃用户
        ,count(distinct case when datediff(user_active_date,user_login_date)=1 then b.userid else null end) as retained_1_uv --次留用户数
        ,count(distinct case when datediff(user_active_date,user_login_date)=3 then b.userid else null end) as retained_3_uv --3日留存用户数
        ,count(distinct case when datediff(user_active_date,user_login_date)=7 then b.userid else null end) as retained_7_uv --7日留存用户数
    from 
    (
      select userid
             ,login_date as user_login_date
      from login_table 
      where login_date>='2021/2/1' and login_date<='2021/2/28'
      group by userid,login_date
    ) a
    left join 
    (
      select userid
             ,login_date as user_active_date
      from login_table 
      where login_date>='2021/2/1' and login_date<='2021/2/28'
      group by userid,login_date
    ) b 
    on a.userid=b.userid
    group by user_login_date
)