如何根据SQL Server select语句中的两列值重新调整值？

Question

请参阅以下内容以了解我的需求:

------------------------------
   Friend       | User 
------------------------------
     2          |  1 
     3          |  2 
     2          |  5
     4          |  2 
------------------------------

当我搜索的价值2,我想我的搜索结果中返回相关的值Friend和User,如下图所示:

--------------------------
      Friends of 2 
--------------------------
        1   - (from column User ) 
        3   - (from column Friend) 
        5   - (from column user ) 
        4   = (from column friend )  

我想要一个列搜索结果如下:

--------------------------
      Friends of 2 
--------------------------
        1  
        3   
        5   
        4   

如何通过在SQL Server中使用SELECT查询来实现此目的？

Answer 1

SELECT Friend FROM MyTable WHERE User = 2
UNION
SELECT User FROM MyTable WHERE Friend = 2;