sql – 如何在同一个表中使用不同的条件两次检索同一列？

Anganbadi_ID               Food     Month
-------------------------------------------    
1165                       ???         1
1165                       ???         2
1165                       ???         4
1168                       ???         4
2032                       ????        4
2218                       ????        4
2219                       ???         4
2358                       ????        4
2546                        ???        10

有4列Anganbadi_ID,Food,Month,Year,我想根据两个不同的月份值比较Food列两次.

例如如果我选择Month = 4作为第一个Food(Food-1)列,Month = 10作为第二个Food(Food-2)列,那么它应该如下::

Anganbadi_ID            Food-1     Food-2    
------------------------------------------    
1165                       ???          NULL 
1168                       ???          NULL 
2032                       ????        NULL 
2218                       ????        NULL 
2219                       ???          NULL 
2358                       ????        NULL 
2546                     NULL        ???

当我尝试这段代码时

SELECT     
   Anganbadi_ID,(SELECT Food
    FROM Anganbadi AS Anganbadi_2
    WHERE (Anganbadi_1.Anganbadi_ID = Anganbadi_ID) 
      AND (Anganbadi_1.Month = 10)
   ) AS 'Food(2)'
FROM Anganbadi AS Anganbadi_1
WHERE (Month = 4)

它显示以下结果::

Anganbadi_ID              Food-1     Food-2    
--------------------------------------------
1165                       ???          NULL 
1168                       ???          NULL 
2032                       ????        NULL 
2218                       ????        NULL 
2219                       ???          NULL 
2358                       ????        NULL

请尽快帮助我….

解决方法

SELECT DISTINCT Anganbadi_ID,(SELECT Food 
 FROM Anganbadi 
 WHERE      (Anganbadi_ID = A.Anganbadi_ID) 
    AND (Month = 4)) AS Food1,(SELECT Food 
 FROM Anganbadi 
 WHERE      (Anganbadi_ID = A.Anganbadi_ID) 
    AND (Month = 10)) AS Food2

FROM Anganbadi AS A 
WHERE A.Month = 10 OR A.Month = 4

SQL Fiddle

（编辑：李大同）

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