T-SQL枢轴？ 从行值创build表列的可能性
实际上是否可以旋转T-SQL（2005），以便（为了参数）第一列的行的值成为输出表的列的标题？
我意识到这不是真正的PIVOT是什么，但这正是我所需要的 – 能够请求一个表，其中列之前并不知道，因为它们已被input到表中的值。
即使是黑客也不错，tbh。
Itzik Ben-Gan关于如何构builddynamicPIVOT的例子，我强烈推荐他的Inside Microsoft SQL Server 2008：T-SQL Programming book
-- Creating and Populating the Orders Table 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 -- Static PIVOT SELECT * FROM (SELECT custid, YEAR(orderdate) AS orderyear, qty FROM dbo.Orders) AS D PIVOT(SUM(qty) FOR orderyear IN([2002],[2003],[2004])) AS P; GO -- Dynamic PIVOT DECLARE @T AS TABLE(y INT NOT NULL PRIMARY KEY); DECLARE @cols AS NVARCHAR(MAX), @y AS INT, @sql AS NVARCHAR(MAX); -- Construct the column list for the IN clause -- eg, [2002],[2003],[2004] SET @cols = STUFF( (SELECT N',' + QUOTENAME(y) AS [text()] FROM (SELECT DISTINCT YEAR(orderdate) AS y FROM dbo.Orders) AS Y ORDER BY y FOR XML PATH('')), 1, 1, N''); -- Construct the full T-SQL statement -- and execute dynamically SET @sql = N'SELECT * FROM (SELECT custid, YEAR(orderdate) AS orderyear, qty FROM dbo.Orders) AS D PIVOT(SUM(qty) FOR orderyear IN(' + @cols + N')) AS P;'; EXEC sp_executesql @sql; GO 稍微好一点的枢轴查询如下：
-- Static PIVOT WITH PivotData AS ( SELECT custid, YEAR(orderdate) AS orderyear, qty FROM dbo.Orders ) SELECT custid, [2002], [2003], [2004] FROM PivotData PIVOT(SUM(qty) FOR orderyear IN([2002],[2003],[2004])) AS P;
我更喜欢公共表expression式（CTE）在派生表上的样式，因为我认为它更容易理解。 Itzik也是如此，因为他在他的书“查询Microsoft SQL Server 2012”中推荐了这种风格。
