sqlserver巧用row_number和partitionby分组取top数据

SQL Server 2005后之后，引入了row_number()函数，row_number()函数的分组排序功能使这种操作变得非常简单

--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 
truncate table #score 
drop table #score 
 
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)