记录一下sqlserver的pivot（行转列）的应用，及遇到的数据无法合并的问题。

 基础语法

SELECT <non-pivoted column>,  
    [first pivoted column] AS <column name>,  
    [second pivoted column] AS <column name>,  
    ...  
    [last pivoted column] AS <column name>  
FROM  
    (<SELECT query that produces the data>)   
    AS <alias for the source query>  
PIVOT  
(  
    <aggregation function>(<column being aggregated>)  
FOR   
[<column that contains the values that will become column headers>]   
    IN ( [first pivoted column], [second pivoted column],  
    ... [last pivoted column])  
) AS <alias for the pivot table>  
<optional ORDER BY clause>;  

pivot合并的数据必须是除了pivot里面指定的列外，其他列的数据都是相同的。 

测试数据如下

代码如下

select [PId],[Field_A] as A,[Field_B] as B,[Field_C] as C,[CreateTime] from 
(
	select [PId]
		  ,[Name]
		  ,[Value]
		  ,[CreateTime]
	  from [T_Test]
) as tt
pivot(max(tt.[Value]) for tt.[Name] in ([Field_A],[Field_B],[Field_C])) as temp
order by [CreateTime]

执行效果如下 

数据没有合并

代码如下

select [PId],[Field_A] as A,[Field_B] as B,[Field_C] as C,[CreateTime] from 
(
	select [Id]
		  ,[PId]
		  ,[Name]
		  ,[Value]
		  ,[CreateTime]
	  from [T_Test]
) as tt
pivot(max(tt.[Value]) for tt.[Name] in ([Field_A],[Field_B],[Field_C])) as temp
order by [CreateTime]

 执行代码发现数据是多行的，并没有合并起来

如图

是什么原因导致数据没有合并？

原因就在于[T_Test]的[Id]，因为他每条数据都是不同的，所以导致数据无法合并。

过滤掉[Id]字段后就可以合并数据。