step1:查找每天每个用户的登录次数;
step2:只显示登录次数中大于等于2次的用户;
step3:统计满足条件的用户的个数;
group by用于分组,group by子句可以包含任意的列。
HAVING子句来指定一组行或聚合的过滤条件
SELECT COUNT(*) as num
From
(SELECT login_date, count(login_time) from logintb group by user_id, login_date having count(login_time)>=2)a;