select a.user_id from login_tb as a 
inner join 
login_tb as b on a.user_id = b.user_id and date(a.log_time)=date(b.log_time)-1 #自联结，条件是某一用户存在第二天的登录记录
inner join login_tb as c on b.user_id = c.user_id and date(b.log_time)= date(c.log_time) -1 #再次自联结，条件是某一用户存在第三天的登录记录
where a.user_id in (select user_id from register_tb) #筛选出新用户
order by a.user_id#排序