group by分组后对组内数据进行排序

查询 每个班级英语成绩最高的前两名的记录

原文：https://www.cnblogs.com/hxfcodelife/p/10226934.html

select a.Classid,a.English from
(select Classid,English,row_number() over(partition by Classid order by English desc) as n
from CJ) a
where n<=2

另外一种情况：取组内最新的数据
select max(create_time),order_id from ycej_loan_info where order_id <> '' group by order_id