sql行转列和列转行(转)

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() 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(, '', , 'A', );
INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)
  VALUES(, '', , 'A', );
INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)
  VALUES(, '', , 'B', );
INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)
  VALUES(, '', , 'A', );
INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)
  VALUES(, '', , 'C', );
INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)
  VALUES(, '', , 'B', );
INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)
  VALUES(, '', , 'A', );
INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)
  VALUES(, '', , 'C', );
INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)
  VALUES(, '', , 'B', );
INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)
  VALUES(, '', , 'C', );
INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty)
  VALUES(, '', , 'D', );
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)= then qty end) as [],
sum(case when YEAR(orderdate)= then qty end) as [],
sum(case when YEAR(orderdate)= then qty end) as []
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([],[],[]))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()
)
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=
 ELSE
  SET @result=
 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()=N'';
WHILE @Y IS NOT NULL
BEGIN
  SET @SQL=@SQL+N',sum(case when YEAR(orderdate)='+CAST(@Y AS NVARCHAR()) +N' then qty end) as '+QUOTENAME(@Y);
  SET @Y=(SELECT MIN(years) from @T where years>@Y);
END
IF  dbo.fn_CheckSQLInjection(@SQL)=
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()=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('')),,,N'');
IF  dbo.fn_CheckSQLInjection(@SQL)=
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([],[],[]))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()=N'';
SET @SQL=STUFF((SELECT N','+QUOTENAME(COLUMN_NAME ) FROM INFORMATION_SCHEMA.COLUMNS
WHERE ORDINAL_POSITION> AND TABLE_NAME='PvtCustOrders'
FOR XML PATH('')),,,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/yexinw/archive/2012/08/31/2665171.html