题解 | #每天的日活数及新用户占比#

select 
    b.dt,
    count(b.uid) dau,
    round(count(a.uid)/count(b.uid),2)  uv_new_ratio
from 
    (
        select 
            uid,
            min(date(in_time)) dt
        from tb_user_log 
        group by uid
    ) a # 新用户首次登陆日期
right join 
    (
        select uid, date(in_time) dt from tb_user_log
        union
        select uid, date(out_time) from tb_user_log
        # 使用union去重合并登入登出表！！！ 而不是用union all（不去重）
        # 用户使用总表
    ) b
on a.uid = b.uid and a.dt = b.dt
group by b.dt
order by b.dt

表B：

表A拼B：