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)。
1 --创建测试环境 2 USE tempdb; 3 GO 4 5 IF OBJECT_ID('dbo.Orders') IS NOT NULL 6 DROP TABLE dbo.Orders; 7 GO 8 9 CREATE TABLE dbo.Orders 10 ( 11 orderid int NOT NULL PRIMARY KEY NONCLUSTERED, 12 orderdate datetime NOT NULL, 13 empid int NOT NULL, 14 custid varchar(5) NOT NULL, 15 qty int NOT NULL 16 ); 17 18 CREATE UNIQUE CLUSTERED INDEX idx_orderdate_orderid 19 ON dbo.Orders(orderdate, orderid); 20 21 INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty) 22 VALUES(30001, '20020802', 3, 'A', 10); 23 INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty) 24 VALUES(10001, '20021224', 1, 'A', 12); 25 INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty) 26 VALUES(10005, '20021224', 1, 'B', 20); 27 INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty) 28 VALUES(40001, '20030109', 4, 'A', 40); 29 INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty) 30 VALUES(10006, '20030118', 1, 'C', 14); 31 INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty) 32 VALUES(20001, '20030212', 2, 'B', 12); 33 INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty) 34 VALUES(40005, '20040212', 4, 'A', 10); 35 INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty) 36 VALUES(20002, '20040216', 2, 'C', 20); 37 INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty) 38 VALUES(30003, '20040418', 3, 'B', 15); 39 INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty) 40 VALUES(30004, '20020418', 3, 'C', 22); 41 INSERT INTO dbo.Orders(orderid, orderdate, empid, custid, qty) 42 VALUES(30007, '20020907', 3, 'D', 30); 43 GO
行转列-静态方案：
1 --行转列的静态方案一：CASE WHEN,兼容sql2000 2 select custid, 3 sum(case when YEAR(orderdate)=2002 then qty end) as [2002], 4 sum(case when YEAR(orderdate)=2003 then qty end) as [2003], 5 sum(case when YEAR(orderdate)=2004 then qty end) as [2004] 6 from orders 7 group by custid; 8 GO 9 --行转列的静态方案二：PIVOT,sql2005及以后版本 10 select * 11 from (select custid,YEAR(orderdate) as years,qty from orders) as ord 12 pivot(sum(qty) for years in([2002],[2003],[2004]))as p 13 GO
行转列-动态方案：加入了xml处理和SQL注入预防判断
1 --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。 2 CREATE FUNCTION [dbo].[fn_CheckSQLInjection] 3 ( 4 @Col nvarchar(4000) 5 ) 6 RETURNS BIT --如果存在可能的注入字符返回true,反之返回false 7 AS 8 BEGIN 9 DECLARE @result bit; 10 IF 11 UPPER(@Col) LIKE UPPER(N'%0x%') 12 OR UPPER(@Col) LIKE UPPER(N'%;%') 13 OR UPPER(@Col) LIKE UPPER(N'%''%') 14 OR UPPER(@Col) LIKE UPPER(N'%--%') 15 OR UPPER(@Col) LIKE UPPER(N'%/*%*/%') 16 OR UPPER(@Col) LIKE UPPER(N'%EXEC%') 17 OR UPPER(@Col) LIKE UPPER(N'%xp_%') 18 OR UPPER(@Col) LIKE UPPER(N'%sp_%') 19 OR UPPER(@Col) LIKE UPPER(N'%SELECT%') 20 OR UPPER(@Col) LIKE UPPER(N'%INSERT%') 21 OR UPPER(@Col) LIKE UPPER(N'%UPDATE%') 22 OR UPPER(@Col) LIKE UPPER(N'%DELETE%') 23 OR UPPER(@Col) LIKE UPPER(N'%TRUNCATE%') 24 OR UPPER(@Col) LIKE UPPER(N'%CREATE%') 25 OR UPPER(@Col) LIKE UPPER(N'%ALTER%') 26 OR UPPER(@Col) LIKE UPPER(N'%DROP%') 27 SET @result=1 28 ELSE 29 SET @result=0 30 return @result 31 END 32 GO 33 34 --行转列的动态方案一：CASE WHEN,兼容sql2000 35 DECLARE @T TABLE (years INT NOT NULL PRIMARY KEY); 36 INSERT INTO @T 37 SELECT DISTINCT YEAR(orderdate) from orders; 38 DECLARE @Y INT; 39 SET @Y=(SELECT MIN(years) from @T); 40 DECLARE @SQL NVARCHAR(4000)=N''; 41 WHILE @Y IS NOT NULL 42 BEGIN 43 SET @SQL=@SQL+N',sum(case when YEAR(orderdate)='+CAST(@Y AS NVARCHAR(4)) +N' then qty end) as '+QUOTENAME(@Y); 44 SET @Y=(SELECT MIN(years) from @T where years>@Y); 45 END 46 IF dbo.fn_CheckSQLInjection(@SQL)=0 47 SET @SQL=N'SELECT custid'+@SQL+N' FROM orders group by custid' 48 PRINT @SQL 49 EXEC sp_executesql @SQL 50 GO 51 52 --行转列的动态方案二：PIVOT,sql2005及以后版本 53 DECLARE @T TABLE (years INT NOT NULL PRIMARY KEY); 54 INSERT INTO @T 55 SELECT DISTINCT YEAR(orderdate) from orders; 56 DECLARE @Y INT; 57 SET @Y=(SELECT MIN(years) from @T); 58 DECLARE @SQL NVARCHAR(4000)=N''; 59 60 --这里使用了xml处理来处理类组字符串 61 SET @SQL=STUFF((SELECT N','+QUOTENAME(years) FROM @T 62 FOR XML PATH('')),1,1,N''); 63 IF dbo.fn_CheckSQLInjection(@SQL)=0 64 SET @SQL=N'select * from (select DISTINCT custid,YEAR(orderdate) as years,qty from orders) as ord 65 pivot(sum(qty) for years in('+@SQL+N'))as p'; 66 PRINT @SQL; 67 EXEC SP_EXECUTESQL @SQL; 68 GO
列转行：
1 --列转行的静态方案：UNPIVOT,sql2005及以后版本 2 SELECT * FROM dbo.pvtCustOrders 3 SELECT custid,years,qty 4 from dbo.pvtCustOrders 5 unpivot(qty for years in([2002],[2003],[2004]))as up 6 GO 7 --列转行的动态方案：UNPIVOT,sql2005及以后版本 8 --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。 9 DECLARE @SQL NVARCHAR(4000)=N''; 10 SET @SQL=STUFF((SELECT N','+QUOTENAME(COLUMN_NAME ) FROM INFORMATION_SCHEMA.COLUMNS 11 WHERE ORDINAL_POSITION>1 AND TABLE_NAME='PvtCustOrders' 12 FOR XML PATH('')),1,1,N'') 13 SET @SQL=N'SELECT custid,years,qty 14 from dbo.pvtCustOrders 15 unpivot(qty for years in('+@SQL+'))as up'; 16 PRINT @SQL; 17 EXEC SP_EXECUTESQL @SQL;
转自：http://www.cnblogs.com/Joe-T/archive/2011/11/28/2266280.html
