1. 查询同一天，同一台移动设备，用不同角色ID登录的统计情况： ~~~ SELECT COUNT(DISTINCT `characterid`) AS count, //分组统计情况 SUBSTRING(`createtime`, 1, 10) AS date, `device` FROM `l_login` WHERE `device` IS NOT NULL AND TRIM(`device`) != '' AND `status` in(1,2) //首次登录或常规登录 GROUP BY `device`, //按手机设备 SUBSTRING(`createtime`, 1, 10) //按照日期 HAVING COUNT(*) > 1 ORDER BY SUBSTRING(`createtime`, 1, 10) DESC, `characterid` DESC ~~~