SQL 行转列和列转行

行列互转，是一个经常遇到的需求。实现的方法，有case when方式和2005之后的内置pivot和unpivot方法来实现。

在读了技术内幕那一节后，虽说这些解决方案早就用过了，却没有系统性的认识和总结过。为了加深认识，再总结一次。

行列互转，可以分为静态互转，即事先就知道要处理多少行（列）;动态互转,事先不知道处理多少行(列)。

--创建测试环境

USE tempdb;

GO

IF OBJECT_ID(‘dbo.Orders‘) IS NOT NULL

  DROP TABLE dbo.Orders;

GO
CREATE TABLE dbo.Orders

(

  orderid   int        NOT NULL PRIMARY KEY NONCLUSTERED,

  orderdate datetime   NOT NULL,

  empid     int        NOT NULL,

  custid    varchar(5) NOT NULL,

  qty       int        NOT NULL

);
CREATE UNIQUE CLUSTERED INDEX idx_orderdate_orderid

  ON dbo.Orders(orderdate, orderid);
INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)

  VALUES(30001, ‘20020802‘, 3, ‘A‘, 10);

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)

  VALUES(10001, ‘20021224‘, 1, ‘A‘, 12);

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)

  VALUES(10005, ‘20021224‘, 1, ‘B‘, 20);

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)

  VALUES(40001, ‘20030109‘, 4, ‘A‘, 40);

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)

  VALUES(10006, ‘20030118‘, 1, ‘C‘, 14);

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)

  VALUES(20001, ‘20030212‘, 2, ‘B‘, 12);

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)

  VALUES(40005, ‘20040212‘, 4, ‘A‘, 10);

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)

  VALUES(20002, ‘20040216‘, 2, ‘C‘, 20);

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)

  VALUES(30003, ‘20040418‘, 3, ‘B‘, 15);

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)

  VALUES(30004, ‘20020418‘, 3, ‘C‘, 22);

INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)

  VALUES(30007, ‘20020907‘, 3, ‘D‘, 30);

GO

行转列-静态方案：

--行转列的静态方案一：CASE WHEN,兼容sql2000

select custid,

sum(case when YEAR(orderdate)=2002 then qty end) as [2002],

sum(case when YEAR(orderdate)=2003 then qty end) as [2003],

sum(case when YEAR(orderdate)=2004 then qty end) as [2004]

from orders

group by custid;

GO

--行转列的静态方案二：PIVOT,sql2005及以后版本

select *

from (select custid,YEAR(orderdate) as years,qty from orders) as ord

pivot(sum(qty) for years in([2002],[2003],[2004]))as p

GO

行转列-动态方案：加入了xml处理和SQL注入预防判断

--既然是用到了动态SQL,就有一个老话题:SQL注入。建一个注入性字符的判断函数。

CREATE FUNCTION [dbo].[fn_CheckSQLInjection]

(

 @Col nvarchar(4000)

)

RETURNS BIT --如果存在可能的注入字符返回true,反之返回false

AS

BEGIN

DECLARE @result bit;

  IF

     UPPER(@Col) LIKE UPPER(N‘%0x%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%;%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%‘‘%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%--%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%/*%*/%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%EXEC%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%xp_%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%sp_%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%SELECT%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%INSERT%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%UPDATE%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%DELETE%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%TRUNCATE%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%CREATE%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%ALTER%‘)

  OR UPPER(@Col) LIKE UPPER(N‘%DROP%‘)

  SET @result=1

 ELSE

  SET @result=0

 return @result

END

GO

--行转列的动态方案一：CASE WHEN,兼容sql2000

DECLARE @T TABLE (years INT NOT NULL PRIMARY KEY);

INSERT INTO @T

SELECT DISTINCT YEAR(orderdate) from orders;

DECLARE @Y INT;

SET @Y=(SELECT MIN(years) from @T);

DECLARE @SQL NVARCHAR(4000)=N‘‘;

WHILE @Y IS NOT NULL

BEGIN

  SET @SQL=@SQL+N‘,sum(case when YEAR(orderdate)=‘+CAST(@Y AS NVARCHAR(4)) +N‘ then qty end) as ‘+QUOTENAME(@Y);

  SET @Y=(SELECT MIN(years) from @T where years>@Y);

END

IF  dbo.fn_CheckSQLInjection(@SQL)=0

SET @SQL=N‘SELECT custid‘+@SQL+N‘ FROM orders group by custid‘

PRINT @SQL

EXEC sp_executesql  @SQL

GO
--行转列的动态方案二：PIVOT,sql2005及以后版本

DECLARE @T TABLE (years INT NOT NULL PRIMARY KEY);

INSERT INTO @T

SELECT DISTINCT YEAR(orderdate) from orders;

DECLARE @Y INT;

SET @Y=(SELECT MIN(years) from @T);

DECLARE @SQL NVARCHAR(4000)=N‘‘;
--这里使用了xml处理来处理类组字符串

SET @SQL=STUFF((SELECT N‘,‘+QUOTENAME(years) FROM @T

 FOR XML PATH(‘‘)),1,1,N‘‘);

IF  dbo.fn_CheckSQLInjection(@SQL)=0

SET @SQL=N‘select * from (select DISTINCT custid,YEAR(orderdate) as years,qty from orders) as ord

pivot(sum(qty) for years in(‘+@SQL+N‘))as p‘;

PRINT @SQL;

EXEC SP_EXECUTESQL @SQL;

GO

列转行：

--列转行的静态方案：UNPIVOT,sql2005及以后版本

SELECT * FROM dbo.pvtCustOrders

SELECT custid,years,qty

from dbo.pvtCustOrders

unpivot(qty for years in([2002],[2003],[2004]))as up

GO

--列转行的动态方案：UNPIVOT,sql2005及以后版本

--因为行是动态所以这里就从INFORMATION_SCHEMA.COLUMNS视图中获取列来构造行，同样也使用了XML处理。

DECLARE @SQL NVARCHAR(4000)=N‘‘;

SET @SQL=STUFF((SELECT N‘,‘+QUOTENAME(COLUMN_NAME ) FROM INFORMATION_SCHEMA.COLUMNS

WHERE ORDINAL_POSITION>1 AND TABLE_NAME=‘PvtCustOrders‘

FOR XML PATH(‘‘)),1,1,N‘‘)

SET @SQL=N‘SELECT custid,years,qty

         from dbo.pvtCustOrders

         unpivot(qty for years in(‘+@SQL+‘))as up‘;

PRINT @SQL;

EXEC SP_EXECUTESQL @SQL;

转自：http://www.cnblogs.com/Joe-T/archive/2011/11/28/2266280.html