如何将主表连接到多个详细信息表，其中额外的详细信息单元格填充为 NULL

Question

我不确定问题标题是否合适。我的问题类似于线程 How to Join Multiple Detail Tables to Header Table 。但这也给出了重复的记录。 这是我的情况
我有一个主表和两个详细表。

MasterID | Name  
-----------------------    // Master table
1          Item1
2          Item2
3          Item3
4          Item4
5          Item5

-----------------------

Det1ID | FKMasterID | Value 
-----------------------------
1         1           Det1-Val1
2         1           Det1-Val2
3         2           Det1-Val3


Det2ID | FKMasterID | Value
-----------------------------
1         1            Det2-Val1
2         1            Det2-Val2
3         1            Det2-Val3
4         3            Det2-Val4
5         5            Det2-Val5
----------------------------------

表格有点像这样。
当我进行所需的左右连接时，我会以这种方式得到结果。

MasterID | Name   | Det1ID | Det1Value | Det2ID | Det2Value
------------------------------------------------------------
1          Item1    1       Det1-Val1    1       Det2-Val1 
1          Item1    1       Det1-Val1    2       Det2-Val2
1          Item1    1       Det1-Val1    3      Det2-Val3
1          Item1    2       Det1-Val2    1       Det2-Val1
1          Item1    2       Det1-Val2    2       Det2-Val2
1          Item1    2       Det1-Val2    3       Det2-Val3
2          Item2    3       Det1-Val3    NULL    NULL
3          Item3    NULL    NULL         4       Det2-Val4
4          Item4    NULL    NULL         NULL    NULL
5          Item5    NULL    NULL         5       Det2-Val5
-------------------------------------------------------------

我期望得到的是

MasterID | Name   | Det1ID | Det1Value | Det2ID | Det2Value
------------------------------------------------------------
1          Item1    1       Det1-Val1    1       Det2-Val1 
1          Item1    2       Det1-Val2    2       Det2-Val2
1          Item1    NULL    NULL         3       Det2-Val3
2          Item2    3       Det1-Val3    NULL    NULL
3          Item3    NULL    NULL         4       Det2-Val4
4          Item4    NULL    NULL         NULL    NULL
5          Item5    NULL    NULL         5       Det2-Val5
------------------------------------------------------------

我不希望任何主项目的详细信息值重复。

有没有办法做到这一点？只有用游标迭代才是方法？？ 一点帮助表示赞赏。

谢谢，

Answer 1

事实证明它比我最初想象的要复杂一些，但下面的方法应该可以解决问题。代码应该很容易解释。

WITH [master] AS(
    SELECT * FROM (VALUES
         (1, 'Item1')
        ,(2, 'Item2')
        ,(3, 'Item3')
        ,(4, 'Item4')
        ,(5, 'Item5')
    ) AS T(ID, Value)
),
Det1 AS (
    SELECT * FROM (VALUES
         (1, 1, 'Det1-Val1')
        ,(2, 1, 'Det1-Val2')
        ,(3, 2, 'Det1-Val3')
    ) AS T(ID, MasterID, Value)
),
Det2 AS (
    SELECT * FROM (VALUES
         (1, 1, 'Det2-Val1')
        ,(2, 1, 'Det2-Val2')
        ,(3, 1, 'Det2-Val3')
        ,(4, 3, 'Det2-Val4')
        ,(5, 5, 'Det2-Val5')
    ) AS T(ID, MasterID, Value)
),
Det1Numbered AS(
    SELECT MasterID     = M.ID ,
           MasterValue  = M.Value ,
           Det1ID       = D.ID ,
           Det1Value    = D.Value, 
           RowNr        = ROW_NUMBER() OVER (PARTITION BY M.ID ORDER BY D.ID)
    FROM  [master] AS M
        LEFT JOIN Det1 AS D
            ON M.ID = D.MasterID
),
Det2Numbered AS(
    SELECT MasterID     = M.ID ,
           MasterValue  = M.Value ,
           Det2ID       = D.ID ,
           Det2Value    = D.Value, 
           RowNr        = ROW_NUMBER() OVER (PARTITION BY M.ID ORDER BY D.ID)
    FROM  [master] AS M
        LEFT JOIN Det2 AS D
            ON M.ID = D.MasterID
)
SELECT MasterID         = COALESCE(D1.MasterID, D2.MasterID),
       MasterValue      = COALESCE(D1.MasterValue, D2.MasterValue),
       D1.Det1ID ,
       D1.Det1Value ,
       D2.Det2ID ,
       D2.Det2Value
FROM Det1Numbered AS D1
    FULL JOIN Det2Numbered AS D2
        ON D1.MasterID = D2.MasterID
        AND D2.RowNr = D1.RowNr
ORDER BY MasterID

编辑：确实有一个小错误，我已经更新了上面的查询。修复方法是将PARTITION BY D.MasterID 替换为PARTITION BY M.ID，现在RowNr 从1 开始，用于之前版本中没有的每个主记录。

Answer 2

我不太确定，但我认为您想要的是：

SELECT m.MasterID, m.Name, d1.DetailsID Det1ID, d1.Value Det1Value, d2.DetailsID Det2ID, d2.Value Det2Value
FROM Details1 d1
    FULL OUTER JOIN Details2 d2 ON d1.FKMasterID = d2.FKMasterID AND d1.Value = d2.Value
    RIGHT JOIN Master m ON d1.FKMasterID = m.MasterID OR d2.FKMasterID = m.MasterID

如果值匹配，这将只显示两个详细信息表，这似乎是您想要的？