身份证号加密
select concat(left(`visitors`.`Card_id`,3),'****',right(`visitors`.`Card_id`,4)) AS `Card_id` from userinfo
时段统计
select HOUR(itime) as hours,CONCAT(HOUR(itime),"点~",HOUR(itime)+1,"点") as hours1,count(0) as count from visitors group by hours ORDER BY hours