如何計算SQL中的2個表？

Question

我有以下2個表：

A (ID, No1, No2,D) 
B (ID, No3, No4,D) 

和表格數據被以下：

甲TABEL數據

ID = 1, No1 = 23, No2 = 45, D = 1 
ID = 2, No1 = 12, No2 = 5, D = 1 
ID = 3, No1 = 14, No2 = 4, D = 1 
ID = 4, No1 = 41, No2 = 12, D = 1 
ID = 5, No1 = 2, No2 = 25, D = 1 
ID = 6, No1 = 3, No2 = 96, D = 1 

乙表數據沒有任何數據

如果我通過以下SQL查詢

SELECT 
    ISNULL(SUM(dbo.A.No1), 0) AS No1Sum, 
    ISNULL(SUM(dbo.B.No3), 0) AS No3Sum, 
    ISNULL(SUM(dbo.A.No1), 0) - ISNULL(SUM(dbo.B.No3), 0) AS Diffrence 
FROM dbo.A LEFT 
OUTER JOIN dbo.B ON dbo.A.id = dbo.B.id 
GROUP BY dbo.B.No3 

那麼下面的數據是未來

No1Sum = 95, No3Sum = 0, Diffrence = 95 

但是當我加入WHERE條件和寫入查詢，則沒有數據在下面的查詢

SELECT 
    ISNULL(SUM(dbo.A.No1), 0) AS No1Sum, 
    ISNULL(SUM(dbo.B.No3), 0) AS No3Sum, 
    ISNULL(SUM(dbo.A.No1), 0) - ISNULL(SUM(dbo.B.No3), 0) AS Diffrence 
FROM dbo.A 
LEFT OUTER JOIN dbo.B ON dbo.A.id = dbo.B.id 
WHERE (dbo.A.D = 1) 
AND (dbo.B.D = 1) GROUP BY dbo.B.No3 

未來如果數據將precent兩個表中，然後結果顯示例如

No1Sum = 95, No3Sum = 10, Diffrence = 85, 

如果我給下面的查詢

SELECT 
    ISNULL(SUM(dbo.A.No1), 0) AS No1Sum, 
    ISNULL(SUM(dbo.B.No3), 0) AS No3Sum, 
    ISNULL(SUM(dbo.A.No1), 0) - ISNULL(SUM(dbo.B.No3), 0) AS Diffrence 
FROM dbo.A 
LEFT OUTER JOIN dbo.B 
    ON dbo.A.id = dbo.B.id 
    AND dbo.A.D = 1 
    AND dbo.B.D = 1 
GROUP BY dbo.B.No3 

然後下面的結果顯示

No1Sum = 570, No3Sum = 0, Diffrence = 570 

（它被求和6次爲一個表有6行）

因此，如何從兩個表，當兩個表中的數據的結果是計算準確的，但是當一個表有數據而B沒有數據時，結果不會到來。

在此先感謝

Answer 1

此查詢不起作用的原因是因爲它只返回dbo.b.d爲1的記錄。但在您的查詢中它有時可以爲null。

SELECT 
    ISNULL(SUM(dbo.A.No1), 0) AS No1Sum, 
    ISNULL(SUM(dbo.B.No3), 0) AS No3Sum, 
    ISNULL(SUM(dbo.A.No1), 0) - ISNULL(SUM(dbo.B.No3), 0) AS Diffrence 
FROM 
     dbo.A LEFT OUTER JOIN dbo.B ON dbo.A.id = dbo.B.id 
WHERE 
     (dbo.A.D = 1) AND (dbo.B.D = 1) GROUP BY dbo.B.No3 

因此改變這一行

(dbo.A.D = 1) AND (dbo.B.D = 1) GROUP BY dbo.B.No3 

對此

(dbo.A.D = 1) AND (isnull(dbo.B.D, 1) = 1) GROUP BY dbo.B.No3 

ISNULL（阿根廷，默認值）設置爲ARG如果arg不爲空，否則，將它設置爲默認值。

Answer 2

我認爲這樣做，即使第二個表有數據。

SELECT ISNULL(SUM(A.No1), 0) AS No1Sum , 
      ISNULL(SUM(B.No3), 0) AS No3Sum , 
      ISNULL(SUM(A.No1), 0) - ISNULL(SUM(B.No3), 0) AS Diffrence 
    FROM A 
      LEFT OUTER JOIN B ON A.id = B.id 

---

SELECT 
    ISNULL(SUM(dbo.A.No1), 0) AS No1Sum, 
    ISNULL(SUM(dbo.B.No3), 0) AS No3Sum, 
    ISNULL(SUM(dbo.A.No1), 0) - ISNULL(SUM(dbo.B.No3), 0) AS Diffrence 
FROM dbo.A 
LEFT OUTER JOIN dbo.B ON dbo.A.id = dbo.B.id 
WHERE (dbo.A.D = 1) 
AND (dbo.B.D = 1) GROUP BY dbo.B.No3 

此查詢不會獲取任何記錄，如果表B沒有任何數據，因爲這種狀態。

WHERE (dbo.A.D = 1) AND (dbo.B.D = 1)  

我想在連接上應用多個條件是開銷。

LEFT OUTER JOIN dbo.B 
    ON dbo.A.id = dbo.B.id 
    AND dbo.A.D = 1 --Overhead 
    AND dbo.B.D = 1 --Overhead