SQL行列互转的处理方法有什么 具体怎样实现
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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; 以上就是关于“SQL行列互转的处理方式有什么，具体怎样实现”的相关知识，感谢各位的阅读，想要掌握这篇文章的知识点还需要大家自己动手实践使用过才能领会，如果想了解更多相关内容的文章，小编每天都会为大家更新不同的知识。 （编辑：银川站长网） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |
