Question

我有使用访问权限的问题：我使用RIGHT + LEFT外连接来克服ACCESS不支持FULL JOIN这一事实。

SELECT *
FROM T1 RIGHT OUTER JOIN T2
ON T1.xxx = T2.xxx 
UNION 
SELECT *
FROM T1 LEFT OUTER JOIN T2
ON T1.xxx = T2.xxx

在这些表格上：

T1:
ID1 | xxx | fieldA
a     1       X
b     2       Y
c     3       Z

T2:
ID2 | xxx | fieldB
d      2       K
e      3       J
f      4       H

结果我获得了一个具有这种结构的表

T1.xxx | T2.xxx | fieldA | fieldB | ID1 | ID2
   1                 X               a
   2        2        Y       K       b     d
   3        3        Z       J       c     e
            4                H             f

xxx不是主键，但具有相同的名称和数字类型（整数）

我从许多其他地方看到，这应该通过折叠两张桌子来实现！这里没有（相同行上的元素，当非空白时，当然是相同的）

我的期望

FINAL TABLE:
    xxx |  ID1 | ID2 |fieldA | fieldB
     1      a            X
     2      b     d      Y       K
     3      c     e      Z       J
     4            f              H

Answer 1

这两个表似乎都有不同的列值集，您可能t1.xxx和t2.xxx具有相同的值，但其他列不是{{1在这种情况下，不会合并这两个记录

尝试类似

的内容

union

这样的内容应该为您提供表1 和表2 中的所有SELECT T1.xxx FROM T1 RIGHT OUTER JOIN T2 ON T1.xxx = T2.xxx UNION SELECT T2.xxx FROM T1 LEFT OUTER JOIN T2 ON T1.xxx = T2.xxx值，忽略xxx的值duplicate }。

Answer 2

您观察到的行为最可能的解释是返回的行不相同，它们不是完全相同的。

UNION运算符将删除重复的行，但它不会对“折叠表”执行任何操作。

要获取指定的结果集（在更新的问题中），这里有一个返回结果的SQL模式。（我不知道Access是否支持此功能，但这可以在MySQL，SQL Server，Oracle等中使用。）

 SELECT i.xxx
      , v1.ID AS ID1
      , v2.ID AS ID2   
      , v1.fieldA AS fieldA   
      , v2.fieldB AS fieldB   
   FROM (
          SELECT t1.xxx AS xxx
            FROM T1 t1
           UNION
          SELECT t2.xxx
            FROM T2 t2
        ) i
   LEFT
   JOIN T1 v1
     ON v1.xxx = i.xxx
   LEFT
   JOIN T2 v2
     ON v2.xxx = i.xxx

（注意：如果不保证xxx在每个表中都是唯一的，那么此查询可能会生成重复的行。）

Answer 3

我的解决方案（绝对不优雅）：

SELECT [QUERY1].XX, ID1, ID2, fieldA, fieldB
FROM (T2 RIGHT JOIN [QUERY1] ON T2.xxx = [QUERY1].XX) LEFT JOIN T1 ON [QUERY1].XX = T1.XX;

其中QUERY1如下：

(SELECT CInt(NZ(T1.xxx,T2.xxx)) as XX
    FROM T1 RIGHT OUTER JOIN T2
    ON T1.xxx = T2.xxx
    UNION 
    SELECT CInt(NZ(T1.xxx,T2.xxx)) as XX 
    FROM T1 LEFT OUTER JOIN T2
    ON T1.xxx = T2.xxx)
    UNION (SELECT CInt(NZ(T2.xxx,T1.xxx))  as xx1
    FROM T1 RIGHT OUTER JOIN T2
    ON T1.xxx = T2.xxx
    UNION 
    SELECT CInt(NZ(T2.xxx,T1.xxx)) as xx1
    FROM T1 LEFT OUTER JOIN T2
    ON T1.xxx = T2.xxx);

请注意，xx1未使用，甚至未在表格中显示

Answer 4

尝试这一个：我尝试过并获得两个结果集。

DECLARE @T1 TABLE
(
ID1 VARCHAR(2) ,XXX INT, FIELDA VARCHAR(2)
)
DECLARE @T2 TABLE
(
ID2 VARCHAR(2) ,XXX INT, FIELDB VARCHAR(2)
)


INSERT INTO @T1 VALUES 
('a',     1,       'X'),
('b',     2,       'Y'),
('c',     3,       'Z')

INSERT INTO @T2 VALUES 
('d',     2,       'k'),
('e',     3,       'j'),
('f',     4,       'h')

SELECT
    ISNULL(CONVERT(VARCHAR(1),T1.xxx),' ') AS [T1.xxx] , 
    ISNULL(CONVERT(VARCHAR(1),T2.xxx),'') AS [T2.xxx] , 
    ISNULL(fieldA,'') AS [fieldA], 
    ISNULL(fieldB,'') AS [fieldB] , 
    ISNULL(ID1,'') AS [ID1] , 
    ISNULL(ID2,'') AS [ID2]
FROM 
(
    SELECT XXX as XXX1 FROM @T1
    UNION
    SELECT XXX as XXX1  FROM @T2
)T LEFT OUTER JOIN 
@T1 T1 ON T.XXX1 = T1.XXX 
LEFT OUTER JOIN
@T2 T2 ON T.XXX1 = T2.XXX

---------------------- RESULT ------------------

T1.xxx  T2.xxx  ID1 ID2 fieldA  fieldB
1       a       X   
2   2   b   d   Y   k
3   3   c   e   Z   j
    4       f       h

SELECT
    ISNULL(CONVERT(VARCHAR(1),T.xxx1),' ') AS [xxx] ,
    ISNULL(ID1,'') AS [ID1] ,   
    ISNULL(ID2,'') AS [ID2],
    ISNULL(fieldA,'') AS [fieldA], 
    ISNULL(fieldB,'') AS [fieldB] 

FROM 
(
    SELECT XXX as XXX1 FROM @T1
    UNION
    SELECT XXX as XXX1  FROM @T2
)T LEFT OUTER JOIN 
@T1 T1 ON T.XXX1 = T1.XXX 
LEFT OUTER JOIN
@T2 T2 ON T.XXX1 = T2.XXX

---------------------- RESULT ------------------

xxx ID1 ID2 fieldA  fieldB
1   a       X   
2   b   d   Y   k
3   c   e   Z   j
4       f       h

MS Access - 替代为具有相同名称的列执行“完全连接”

4 个答案: