Sql 小技巧（持续汇总）

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