[转]Sql Server 2005 行转列的实现

SQL SERVER 2005中新增加了两个关系运算符 PIVOT/ UNPIVOT，能够实现表中的列转换到行，以及行到列的转换工作。
举例，还是先创建测试数据表

 

CREATE TABLE salesByMonth
(
year char(4),
month char(3),
amount money,
PRIMARY KEY (year, month)
)

 

INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','Jan', 789.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','Feb', 389.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','Mar', 8867.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','Apr', 778.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','May', 78.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','Jun', 9.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','Jul', 987.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','Aug', 866.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','Sep', 7787.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','Oct', 85576.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','Nov', 855.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2004','Dec', 5878.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2005','Jan', 7.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2005','Feb', 6868.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2005','Mar', 688.0000)
INSERT INTO salesByMonth (year, month, amount)
VALUES('2005','Apr', 9897.0000)

 

 

我们想要得到类似这样的结果：

Year  Jan            Feb             Mar       …………..

—– ———- ———– ———–

2004 789.0000 389.0000     8867.0000 ………….

2005 7.0000     6868.0000   688.0000 …………..

 

SELECT year,
SUM(case when month = 'Jan' then amount else Null end) AS 'Jan',
SUM(case when month = 'Feb' then amount else Null end) AS 'Feb',
SUM(case when month = 'Mar' then amount else Null end) AS 'Mar',
SUM(case when month = 'Apr' then amount else Null end) AS 'Apr',
SUM(case when month = 'May' then amount else Null end) AS 'May',
SUM(case when month = 'Jun' then amount else Null end) AS 'Jun',
SUM(case when month = 'Jul' then amount else Null end) AS 'Jul',
SUM(case when month = 'Aug' then amount else Null end) AS 'Aug',
SUM(case when month = 'Sep' then amount else Null end) AS 'Sep',
SUM(case when month = 'Oct' then amount else Null end) AS 'Oct',
SUM(case when month = 'Nov' then amount else Null end) AS 'Nov',
SUM(case when month = 'Dec' then amount else Null end) AS 'Dec'
FROM salesByMonth
GROUP by year

 

但这样事实上还是相当麻烦的，现在SQLSERVER2005中有更方便的实现方法。

SELECT Year,[Jan],[Feb],[Mar],[Apr],[May],[Jun],[Jul],[Aug],[Sep],[Oct],[Nov],[Dec]
FROM (
 SELECT year, amount, month
 FROM salesByMonth ) AS salesByMonth
PIVOT ( SUM(amount) FOR month IN
  ([Jan],[Feb],[Mar],[Apr],[May],[Jun],[Jul],[Aug],[Sep],[Oct],[Nov],[Dec])
  ) AS ourPivot
ORDER BY Year

 

就是这样，很简单的用法，效果是完全一样的。

我们再尝试一下把year去掉：

SELECT [Jan],[Feb],[Mar],[Apr],[May],[Jun],[Jul],[Aug],[Sep],[Oct],[Nov],[Dec]
FROM ( SELECT amount, month
FROM salesByMonth ) AS salesByMonth
PIVOT ( SUM(amount) FOR month IN
([Jan],[Feb],[Mar],[Apr],[May],[Jun],[Jul],[Aug],[Sep],[Oct],[Nov],[Dec])
) AS ourPivot

 

 

得到的结果是：

Jan                 Feb                 Mar             …

———- ———— ———–

796.0000     7257.0000     9555.0000     …

同一个月份的数据累加到一起。

 

转自:http://www.zu14.cn/2008/12/04/sql2005/