SQL 右联接返回空行

Question

我正在尝试加入以下表格：

Table答：

Type1   Type2   ID  Object  Location
Sample  Dummy   1   X111    111222
Sample  Dummy   2   X333    333444
Sample  Dummy   2   X333    555666
Sample  Red     1   X222    666777
Test    Red     1   X222    666777
Test    Red     1   X222    666777

Table乙：

Source  Type2   ID  Object  Logged
SR1     Dummy   1   X111    17
SR1     Dummy   2   X333    1
SR1     Red     1   X222    12
SR2     Dummy   1   X111    9
SR2     Dummy   2   X333    9
SR2     Red     1   X222    20

我的SQL代码：

SELECT B.Source, B.Type2, B.ID, B.Object, B.Logged, A.Location 
FROM A RIGHT JOIN B ON 
    A.Type1='Sample' AND 
    A.Type2=B.Type2 AND 
    A.ID=B.ID AND 
    A.Object=B.Object 
WHERE B.Source='SR2'

我期待以下结果：

Source  Type2   ID  Object  Logged  Location
SR1     Dummy   1   X111    17      111222
SR1     Dummy   2   X333    1       333444
SR1     Dummy   2   X333    1       555666
SR1     Red     1   X222    12      666777

但我得到的是这个：

Source  Type2   ID  Object  Logged  Location
SR1     Dummy   1   X111    17      111222
SR1     Dummy   2   X333    1       -
SR1     Dummy   2   X333    1       -
SR1     Red     1   X222    12      666777

我的代码有什么问题？请帮忙。

Answer 1

LEFT JOIN 更容易理解。问题是 b.Type1 = 'Sample' 上的过滤。据我所知，这不是必需的：

SELECT B.Source, B.Type2, B.ID, B.Object, B.Logged, A.Location 
FROM B LEFT JOIN
     A 
     ON A.Type2 = B.Type2 AND 
        A.ID = B.ID AND 
        A.Object = B.Object 
WHERE B.Source = 'SR2';

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