SQL中ROW_NUMBER() 使用

--语法形式：　　　　ROW_NUMBER() OVER(PARTITION BY COL1 ORDER BY COL2) 
--解释：   　　　　根据COL1分组，在分组内部根据 COL2排序，而此函数计算的值就表示每组内部排序后的顺序编号（组内连续的唯一的)
--常用的使用场景： 取每个学科的前3名
--1.创建测试表 
create table #score 
( 
name varchar(20), 
subject varchar(20), 
score int 
) 

--2.插入测试数据 
insert into #score(name,subject,score) values(\'张三\',\'语文\',98) 
insert into #score(name,subject,score) values(\'张三\',\'数学\',80) 
insert into #score(name,subject,score) values(\'张三\',\'英语\',90) 
insert into #score(name,subject,score) values(\'李四\',\'语文\',88) 
insert into #score(name,subject,score) values(\'李四\',\'数学\',86) 
insert into #score(name,subject,score) values(\'李四\',\'英语\',88) 
insert into #score(name,subject,score) values(\'李明\',\'语文\',60) 
insert into #score(name,subject,score) values(\'李明\',\'数学\',86) 
insert into #score(name,subject,score) values(\'李明\',\'英语\',88) 
insert into #score(name,subject,score) values(\'林风\',\'语文\',74) 
insert into #score(name,subject,score) values(\'林风\',\'数学\',99) 
insert into #score(name,subject,score) values(\'林风\',\'英语\',59) 
insert into #score(name,subject,score) values(\'严明\',\'英语\',96) 

--3.取每个学科的前3名数据 
select * from 
( 
select subject,name,score,ROW_NUMBER() over(PARTITION by subject order by score desc) as num from #score 
) T where T.num <= 3 order by subject 

--4.删除临时表 drop table #score  

结果：