基于多个字段的完整外连接

Question

这是我面临的情况：

我有两个表A和B。如果记录在表A中而不在表B中，则需要将它们添加到表B中。如果记录在表B中而不在表A中，那么它们需要从表 B 中删除。这里的技巧是，它是两个键的混合，这使得

Table A    
Operation_Key    Part_Key  
1                1
1                2
2                1
2                3

Table B
Operation_Key    Part_Key  Record_Key
1                1         1
2                1         2
2                3         3
2                4         4

我试图获得正确类型的查询的唯一组合，以便返回的结果看起来像

Results
Operation_Key        Part_Key  Record_Key   Action
1                    2         NULL         Add
2                    4         4            Delete

我的查询到目前为止看起来与此类似：

CREATE TABLE #Action_Table
(
  Action VARCHAR(6),
  Action_Bit INT,
  Operation_Key INT,
  Record_Key INT,
  Part_Key INT
)
INSERT INTO #Action_Table
SELECT 
  CASE
    WHEN WS.Operation_Key IS NULL THEN 'Delete'
    WHEN WS.Operation_Key IS NOT NULL THEN 'Add'
  END Action,
  CASE
    WHEN WS.Operation_Key IS NULL THEN '0'
    WHEN WS.Operation_Key IS NOT NULL THEN '1'
  END Action_Bit,
  CASE
    WHEN WS.Operation_Key IS NULL THEN WC.Operation_Key
    WHEN WS.Operation_Key IS NOT NULL THEN WS.Operation_Key
  END Operation_Key,
  CASE
    WHEN WS.Operation_Key IS NULL THEN WC.Record_Key
    WHEN WS.Operation_Key IS NOT NULL THEN NULL
  END Workcenter_Component_Key,
  CASE
    WHEN WS.Operation_Key IS NULL THEN WC.Part_Key
    WHEN WS.Operation_Key IS NOT NULL THEN WS.Part_Key
  END Part_Key
FROM #WS_Part_Table WS
FULL OUTER JOIN #WC_Part_Table WC
  ON WC.Part_Key = WS.Part_Key
 AND WC.Operation_Key = WS.Operation_Key
WHERE (WS.Part_Key IS NULL or WC.Part_Key IS NULL) AND (WS.Operation_Key IS NULL or WC.Operation_Key IS NULL)

#WS_Part_Table 和 #WC_Part_Table 都是我使用查询构建的临时表，但我的困境是我必须预查询我感兴趣的操作键，否则我会得到太多结果。

这是我用来创建 #WC_Part_Table 的查询

    CREATE TABLE #WC_Part_Table
    (
      Operation_Key INT,
      Record_Key INT,
      Part_Key INT
    )
    -- Workcenter Component Table
    INSERT INTO #WC_Part_Table
    SELECT
      O.Operation_Key,
      WC.Record_Key,
      WC.Part_Key
    FROM Workcenter_Component WC
    JOIN Operation O
      ON O.Default_Workcenter_Key = WC.Workcenter_Key

 /* There is some reason why this next line is needed */
    WHERE O.Operation_Key = 23149

Answer 1

执行此操作即可获取您发布的结果：

SELECT COALESCE(a.Operation_Key, b.Operation_Key) Operation_Key,
             COALESCE(a.Part_Key, b.Part_Key) Part_Key,
             Record_Key,
             CASE 
                WHEN Record_Key IS NULL THEN 'Add'
                ELSE 'Delete'
            END Action
  FROM TableA a FULL OUTER JOIN TableB b
      ON a.Operation_Key = b.Operation_Key
        AND a.Part_Key = b.Part_Key
 WHERE (a.Operation_Key IS NULL) OR (b.Operation_Key IS NULL)

测试脚本：

CREATE TABLE #TableA     
(       
    Operation_Key INT,       
    Part_Key INT
) 

INSERT INTO #TableA
SELECT 1,1 
UNION
SELECT 1,2 
UNION
SELECT 2,1 
UNION
SELECT 2,3 

CREATE TABLE #TableB
(       
    Operation_Key INT,       
    Part_Key INT,
    Record_Key INT
) 

INSERT INTO #TableB
SELECT 1,1,1 
UNION
SELECT  2,1,2
UNION
SELECT 2,3,3 
UNION
SELECT 2,4,4 


SELECT  COALESCE(a.Operation_Key, b.Operation_Key) Operation_Key,              
                COALESCE(a.Part_Key, b.Part_Key) Part_Key,              
                Record_Key,              
                CASE                  
                    WHEN Record_Key IS NULL THEN 'Add'                 
                    ELSE 'Delete'             
                END Action   
    FROM    #TableA a FULL OUTER JOIN #TableB b       
        ON  a.Operation_Key = b.Operation_Key         
     AND    a.Part_Key = b.Part_Key  
 WHERE (a.Operation_Key IS NULL) OR (b.Operation_Key IS NULL) 

输出：

Operation_Key   Part_Key    Record_Key  Action
1   2   NULL    Add
2   4   4   Delete

Answer 2

添加到 B：

insert into B (Operation_Key, Part_Key, Record_Key)
values
select Operation_Key, Part_Key, null as Record_Key from A
left join b on a.Operation_Key = b.Operation_Key and
a.Part_Key = b.Part_Key
where b.Part_Key is null

从 B 删除：

Delete from B
select * from B left join A on b.Operation_Key = a.Operation_Key and
    b.Part_Key = a.Part_Key
where a.Operation_Key is null

Answer 3

通过巧妙地使用 SQL“COALESCE”运算符，您可以准确地获得您想要的结果表（查看您设置的示例）。如果您使用这样的查询：

SELECT
    COALESCE(A.Operation_Key, B.Operation_Key) as Operation_Key,
    COALESCE(A.part_key, B.part_key) as Part_Key,
    B.Record_Key,
    CASE WHEN A.Operation_Key IS NULL THEN
        'Delete'
    ELSE
        'Add'
    END AS [Action] FROM A
FULL OUTER JOIN B 
    ON A.Operation_Key = B.Operation_Key 
        AND A.Part_Key= B.Part_Key
WHERE A.Operation_Key IS NULL 
    OR B.Operation_Key IS NULL

...您将得到一个与您的示例完全相同的结果表。