sql server 2005中的分区函数用法(partition by 字段)
partition by关键字是分析性函数的一部分，它和聚合函数不同的地方在于它能返回一个分组中的多条记录，而聚合函数一般只有一条反映统计值的记录，partition by用于给结果集分组，如果没有指定那么它把整个结果集作为一个分组
create database StudentDB
go
use StudentDB
go
create table Student --学生成绩表
(
id int, --主键
Grade int, --班级
Score int --分数
)
go
insert Student
select 1,1,88
union all select 2,1,66
union all select 3,1,75
union all select 4,2,30
union all select 5,2,70
union all select 6,2,80
union all select 7,2,60
union all select 8,3,90
union all select 9,3,70
union all select 10,3,80
go
--所有学生信息
select * from Student
id Grade Score
----------- ----------- -----------
1 1 88
2 1 66
3 1 75
4 2 30
5 2 70
6 2 80
7 2 60
8 3 90
9 3 70
10 3 80
(10 行受影响)
--不分班按学生成绩排名
select *,ROW_NUMBER() over(order by Score desc) as Sequence from Student
id Grade Score Sequence
----------- ----------- ----------- --------------------
8 3 90 1
1 1 88 2
6 2 80 3
10 3 80 4
3 1 75 5
9 3 70 6
5 2 70 7
2 1 66 8
7 2 60 9
4 2 30 10
(10 行受影响)
--分班后按学生成绩排名
select *,row_number() over(partition by Grade order by Score desc) as Sequence from Student
id Grade Score Sequence
----------- ----------- ----------- --------------------
1 1 88 1
3 1 75 2
2 1 66 3
6 2 80 1
5 2 70 2
7 2 60 3
4 2 30 4
8 3 90 1
10 3 80 2
9 3 70 3
(10 行受影响)
补充：
msdn-OVER 子句
http://msdn.microsoft.com/zh-cn/library/ms189461.aspx
B.将 OVER 子句与聚合函数结合使用
下面的示例对于查询返回的所有行将 OVER 子句与聚合函数一起使用。 在这个示例中，使用 OVER 子句与使用子查询相比，可以更高效地派生聚合值。
USE AdventureWorks2012;
GO
SELECT SalesOrderID, ProductID, OrderQty
,SUM(OrderQty) OVER(PARTITION BY SalesOrderID) AS Total
,AVG(OrderQty) OVER(PARTITION BY SalesOrderID) AS "Avg"
,COUNT(OrderQty) OVER(PARTITION BY SalesOrderID) AS "Count"
,MIN(OrderQty) OVER(PARTITION BY SalesOrderID) AS "Min"
,MAX(OrderQty) OVER(PARTITION BY SalesOrderID) AS "Max"
FROM Sales.SalesOrderDetail
WHERE SalesOrderID IN(43659,43664);
GO
下面是结果集：
SalesOrderID ProductID OrderQty Total Avg Count Min Max ------------ ----------- -------- ----------- ----------- ----------- ------ ------ 43659 776 1 26 2 12 1 6 43659 777 3 26 2 12 1 6 43659 778 1 26 2 12 1 6 43659 771 1 26 2 12 1 6 43659 772 1 26 2 12 1 6 43659 773 2 26 2 12 1 6 43659 774 1 26 2 12 1 6 43659 714 3 26 2 12 1 6 43659 716 1 26 2 12 1 6 43659 709 6 26 2 12 1 6 43659 712 2 26 2 12 1 6 43659 711 4 26 2 12 1 6 43664 772 1 14 1 8 1 4 43664 775 4 14 1 8 1 4 43664 714 1 14 1 8 1 4 43664 716 1 14 1 8 1 4 43664 777 2 14 1 8 1 4 43664 771 3 14 1 8 1 4 43664 773 1 14 1 8 1 4 43664 778 1 14 1 8 1 4
以下示例显示在计算所得值中将 OVER 子句与聚合函数结合使用。
USE AdventureWorks2012;
GO
SELECT SalesOrderID, ProductID, OrderQty
,SUM(OrderQty) OVER(PARTITION BY SalesOrderID) AS Total
,CAST(1. * OrderQty / SUM(OrderQty) OVER(PARTITION BY SalesOrderID)
*100 AS DECIMAL(5,2))AS "Percent by ProductID"
FROM Sales.SalesOrderDetail
WHERE SalesOrderID IN(43659,43664);
GO
下面是结果集：注意，聚合由 SalesOrderID 计算，并会为每个 SalesOrderID 的每一行计算 Percent by ProductID（ProductID 的百分比）。
SalesOrderID ProductID OrderQty Total Percent by ProductID ------------ ----------- -------- ----------- --------------------------------------- 43659 776 1 26 3.85 43659 777 3 26 11.54 43659 778 1 26 3.85 43659 771 1 26 3.85 43659 772 1 26 3.85 43659 773 2 26 7.69 43659 774 1 26 3.85 43659 714 3 26 11.54 43659 716 1 26 3.85 43659 709 6 26 23.08 43659 712 2 26 7.69 43659 711 4 26 15.38 43664 772 1 14 7.14 43664 775 4 14 28.57 43664 714 1 14 7.14 43664 716 1 14 7.14 43664 777 2 14 14.29 43664 771 3 14 21.4 43664 773 1 14 7.14 43664 778 1 14 7.14