select count(*) from student group by yuanxi_id;
select yuanxi_id from student group by yuanxi_id having count(*) >= all(select count(*) from student group by yuanxi_id);
select yuanxi_name from yuanxi where id in(select yuanxi_id from student group by yuanxi_id having count(*) >= all(select count(*) from student group by yuanxi_id));