如何根据变量重命名列

Question

我想基于变量重命名一系列查询结尾处的列。这将是这样执行的东西：

DECLARE @formTable TABLE (FormID varchar(max)) 
    INSERT @formTable SELECT 'Form1'AS FormID; 
    INSERT @formTable SELECT 'Form2'AS FormID; 
    INSERT @formTable SELECT 'Form3' AS FormID; 
    INSERT @formTable SELECT 'Form5'  AS FormID; 


DECLARE @CCount TABLE (FormID varchar(max), Present varchar(max)) 
    INSERT @CCount SELECT 'Form1' AS FormID, 'Yes' AS Present; 
    INSERT @CCount SELECT 'Form2' AS FormID, 'Yes' AS Present; 

DECLARE @subject varchar(12); 
SET @subject = 'Subject 22' 

SELECT t.FormID AS Form, Present 
FROM @formTable t LEFT JOIN @CCount c ON t.FormID = c.FormID 

中创建一个表，看起来像这样：我希望它看起来像这样

Form  Present 
Form1  Yes 
Form2  Yes 
Form3  NULL 
Form5  NULL 

：

Form  Subject 22 
    Form1  Yes 
    Form2  Yes 
    Form3  NULL 
    Form5  NULL 

我怎样才能做到这一点？

谢谢！

Answer 1

你不能使用变量作为列名 - 你可以使用dynamic SQL这样做，尽管你需要非常小心的使用动态SQL而不是引入SQL injection vulnerability。

Answer 2

一种方法是动态SQL：

declare @sql nvarchar(max) 
set @sql = 'SELECT t.FormID AS Form, Present as [' + @subject + 
    '] FROM @formTable t LEFT JOIN @CCount c ON t.FormID = c.FormID' 
exec @sql