43

I have multiple outer joins

SELECT  A.column2
        , B.column2
        , C.column2
FROM 
(
    (SELECT month, column2 FROM table1) A
    FULL OUTER JOIN
    (SELECT month, column2 FROM table2) B on A.month= B.month
    FULL OUTER JOIN 
    (SELECT month, column2 FROM table3) C on A.month= C.month
)

Now the last join is having a problem, its repeating when month of A is more than B but if B has more month that A we have OUTER JOIN in C with month of A which now repeats, so I guess having a FULL OUTER JOIN within two table might solve the problem?? Any indepth links??

Sample Data(Incorrect)

╔════════════╦═════════╦═════════════╗
║  Revenue   ║ Budget  ║ ActualMonth ║
╠════════════╬═════════╬═════════════╣
║     6.9172 ║ 3.5046  ║ Jan         ║
║     7.3273 ║ 3.7383  ║ Feb         ║
║     7.3273 ║ 3.9719  ║ Mar         ║
║     7.2726 ║ 4.2056  ║ Apr         ║
║     7.2595 ║ 6.7757  ║ May         ║
║     7.2726 ║ 6.7757  ║ Jun         ║
║     0.41   ║ 0.00    ║ Jul         ║
║     0.41   ║ 0.00    ║ Aug         ║
║     0.41   ║ 0.00    ║ Sep         ║
║     0.41   ║ 0.00    ║ Oct         ║
║     7.4696 ║ 0.00    ║ Nov         ║
║     7.4696 ║ 0.00    ║ Dec         ║
║     0.00   ║ 9.3457  ║ Sep         ║
║     0.00   ║ 16.3551 ║ Dec         ║
║     0.00   ║ 6.3084  ║ Jul         ║
║     0.00   ║ 14.0186 ║ Oct         ║
║     0.00   ║ 16.3551 ║ Nov         ║
║     0.00   ║ 6.1915  ║ Aug         ║
╚════════════╩═════════╩═════════════╝

Correct Data

╔════════════╦═════════╦═════════════╗
║  Revenue   ║ Budget  ║ ActualMonth ║
╠════════════╬═════════╬═════════════╣
║     6.9172 ║ 3.5046  ║ Jan         ║
║     7.3273 ║ 3.7383  ║ Feb         ║
║     7.3273 ║ 3.9719  ║ Mar         ║
║     7.2726 ║ 4.2056  ║ Apr         ║
║     7.2595 ║ 6.7757  ║ May         ║
║     7.2726 ║ 6.7757  ║ Jun         ║
║     0.41   ║ 6.3084  ║ Jul         ║
║     0.41   ║ 6.1915  ║ Aug         ║
║     0.41   ║ 9.3457  ║ Sep         ║
║     0.41   ║ 14.0186 ║ Oct         ║
║     7.4696 ║ 16.3551 ║ Nov         ║
║     7.4696 ║ 16.3551 ║ Dec         ║
╚════════════╩═════════╩═════════════╝
4

6 回答 6

60 
SELECT  A.column2
        , B.column2
        , C.column2
FROM 
(
    (SELECT month, column2 FROM table1) A
    FULL OUTER JOIN
    (SELECT month, column2 FROM table2) B on A.month= B.month
    FULL OUTER JOIN 
    (SELECT month, column2 FROM table3) C on ISNULL(A.month, B.month) = C.month
)
于 2013-04-25T14:17:43.593 回答
19

执行此操作的方法之一是从所有三个表中的所有可能数据创建“锚”表，然后使用left outer join：

select
    A.column2,
    B.column2,
    C.column2
from (
    select distinct month from table1
    union
    select distinct month from table2
    union
    select distinct month from table3
) as X
    left outer join table1 as A on A.month = X.month
    left outer join table2 as B on B.month = X.month
    left outer join table3 as C on C.month = X.month
于 2015-04-16T12:00:06.360 回答
6

使用带有COALESCE函数的选项来确定列分组。 

SELECT COALESCE(t1.Month, t2.Month, t3.Month) AS Month, 
       SUM(ISNULL(t1.Col1, 0)) AS t1Col1, 
       SUM(ISNULL(t2.Col1, 0)) AS t2Col1, 
       SUM(ISNULL(t3.Col1, 0)) AS t3Col1
FROM dbo.table1 t1 FULL OUTER JOIN dbo.table2 t2 ON t1.Month = t2.Month
                   FULL OUTER JOIN dbo.table3 t3 ON t1.Month = t3.Month
GROUP BY COALESCE(t1.Month, t2.Month, t3.Month)
于 2013-04-25T14:13:27.150 回答
5

我可以想到 2 种方法来解决这个问题，具体取决于定义您想要的结果的实际逻辑。

第一种也是最简单的方法是使用 GROUP BY month，并使用 MAX(column2) 之类的聚合函数仅获取非零行，或者如果要添加多个非零行，请使用和（）。如果有一个聚合函数可以满足您的逻辑意图，这是最好的解决方案。

另一种是在您的 JOIN 中包含更多条件，例如“WHERE a.month=b.month AND b.column2 > 0”，但如果可能有多个非零行，这仍然无法解决问题。

于 2013-04-23T13:33:45.507 回答
2

就像是

select month, sum(a) a,  sum(b) b, sum(c) c from (
  SELECT month, column2 A, 0 B, 0 C FROM table1 
    union 
  SELECT month, 0 A, column2 B, 0 C FROM table2
    union 
  SELECT month, 0 A, 0 B, column2 C FROM table3
) x
group by month
于 2013-04-23T13:49:39.803 回答
1

与其一次做所有的外连接，不如像这样一次做一个：

SELECT  A.column2
        , B.column2
        , C.column2
FROM 
(
    (SELECT month, column2 FROM (
        (SELECT month, column2 FROM table1) A
        FULL OUTER JOIN
        (SELECT month, column2 FROM table2) B on A.month= B.month
    )) A_AND_B
    FULL OUTER JOIN 
    (SELECT month, column2 FROM table3) C on A_AND_B.month= C.month
)

即，对A和B进行完全外连接，然后对那个和C进行完全外连接，然后对那个和D进行完全外连接，然后对那个和E进行完全外连接，等等。

这不像上面的其他答案那么复杂，并且可以为尽可能多的表重复进行完全外连接。

于 2021-01-24T05:46:22.703 回答