1. 用sql语句查询同一天同一人出现次数超过2次的人名
select name,date,count(*) count from users group by date,name having count(*)=max(count)
2. 查询与某一个人同省份的所有学生的信息的sql语句
select * from 表 where [表内省份字段] = (select [表内省份字段] from 表 where [表中姓名字段] ='[某一个人]')
或者：
select * from 表 as tba where EXISTS(select 1 from 表 where [表中姓名字段] ='[某一个人]' and [表内省份字段]=tba. [表内省份字段])