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 ║
╚════════════╩═════════╩═════════════╝
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
)
One of the ways to do this could be create "anchor" table from all possible data from all three tables and then use 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
I can think of 2 ways off the bat that you can address this, depending on what the actual logic is to define the results you want.
The first, and most fool-proof way, is to use GROUP BY month, and use aggregate functions like MAX(column2) to get the non-zero rows only, or if there are multiple non-zero rows you want to add, use SUM(). This is the best solution if there is an aggregate function that fulfills your logical intent.
Another is to include more conditions in your JOIN, like "WHERE a.month=b.month AND b.column2 > 0", but that still won't solve the problem if there can be more than one non-zero row.
Use option with COALESCE function to determine a column grouping.
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)
something like
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
来源：https://stackoverflow.com/questions/16167902/multiple-full-outer-join-on-multiple-tables