SQL SELECT Sum 值不包括重复项

Question

我正在努力解决 Oracle SQL 中的一个问题。

我将举例说明。我要查询三个表：

Employees
__________________________________________
| EmployeeID | Name                      |
| 1          | John Smith                |
| 2          | Douglas Hoppalot          |
| 3          | Harry Holiday             |
... 



InternalCosts
________________________________
| IntID | Amount | EmployeeID  |
| 1     | 10     |     1       |
| 2     | 20     |     2       |
| 3     | 30     |     1       |
...


ExternalCosts
________________________________
| ExtID | Amount | EmployeeID  |
| 1     | 40     |     1       |
| 2     | 50     |     2       |
| 3     | 60     |     1       |
...

我想要实现的是每个员工一行的结果，以及他们每个内部和外部成本的总和，即

____________________________________________________________
| Name             | InternalCostTotal | ExternalCostTotal |
| John Smith       | 40                | 100               |
| Douglas Hoppalot | 20                | 50                |
...

我遇到的问题是，当我同时查询 InternalCosts 和 ExternalCosts 表时，我得到了每个成本排列，而不仅仅是每个员工一个。当我按员工姓名分组并对金额字段求和时，值太高了。我尝试过的：

SELECT emp.Name, sum(int.Amount), sum(ext.Amount) 
FROM Employees emp,
     InternalCosts int,
     ExternalCosts ext
WHERE emp.EmployeeId = int.EmployeeID
  and emp.EmployeeID = ext.EmployeeID
GROUP BY emp.Name

上面的例子会返回：

 ____________________________________________________________
 | Name             | InternalCostTotal | ExternalCostTotal |
 | John Smith       | 80                | 200               | <- too high!
 | Douglas Hoppalot | 20                | 50                |
 ...

感谢任何帮助/建议/想法！

Answer 1

您应该在 int 和 ext 上使用子查询进行求和，并加入子查询。

我还建议使用显式 JOIN，而不是表、表、表

例如

SELECT emp.Name, int.Amount AS InternalCostTotal, ext.Amount AS ExternalCostTotal
FROM Employees emp
JOIN ( 
    SELECT EmployeeID, SUM(Amount) AS Amount 
    FROM InternalCosts 
    GROUP BY EmployeeID 
) int ON emp.EmployeeId = int.EmployeeID
JOIN ( 
    SELECT EmployeeID, SUM(Amount) AS Amount 
    FROM ExternalCosts 
    GROUP BY EmployeeID 
) ext ON emp.EmployeeId = ext.EmployeeID

Answer 2

SQL Fiddle

Oracle 11g R2 架构设置：

CREATE TABLE Employees ( EmployeeID, Name ) AS
          SELECT 1, 'John Smith' FROM DUAL
UNION ALL SELECT 2, 'Douglas Hoppalot' FROM DUAL
UNION ALL SELECT 3, 'Harry Holiday' FROM DUAL;

CREATE TABLE InternalCosts ( IntID, Amount, EmployeeID ) AS
          SELECT 1, 10, 1 FROM DUAL
UNION ALL SELECT 2, 20, 2 FROM DUAL
UNION ALL SELECT 3, 30, 1 FROM DUAL;

CREATE TABLE ExternalCosts ( ExtID, Amount, EmployeeID ) AS
          SELECT 1, 40, 1 FROM DUAL
UNION ALL SELECT 2, 50, 2 FROM DUAL
UNION ALL SELECT 3, 60, 1 FROM DUAL;

查询 1：

SELECT e.*,
       ( SELECT SUM( Amount ) FROM InternalCosts i WHERE e.EmployeeID = i.EmployeeID ) AS InternalCostTotal,
       ( SELECT SUM( Amount ) FROM ExternalCosts x WHERE e.EmployeeID = x.EmployeeID ) AS ExternalCostTotal
FROM   Employees e

Results：

| EMPLOYEEID |             NAME | INTERNALCOSTTOTAL | EXTERNALCOSTTOTAL |
|------------|------------------|-------------------|-------------------|
|          1 |       John Smith |                40 |               100 |
|          2 | Douglas Hoppalot |                20 |                50 |
|          3 |    Harry Holiday |            (null) |            (null) |

或者（使用连接）：

WITH InternalTotals AS (
  SELECT EmployeeID,
         SUM( Amount ) AS InternalCostTotal
  FROM   InternalCosts
  GROUP BY
         EmployeeID
),
ExternalTotals AS (
  SELECT EmployeeID,
         SUM( Amount ) AS ExternalCostTotal
  FROM   ExternalCosts
  GROUP BY
         EmployeeID
)
SELECT e.EmployeeID,
       i.InternalCostTotal,
       x.ExternalCostTotal
FROM   Employees e
       LEFT OUTER JOIN
       InternalTotals i
       ON ( e.EmployeeID = i.EmployeeID )
       LEFT OUTER JOIN
       ExternalTotals x
       ON ( e.EmployeeID = x.EmployeeID );

Answer 3

这应该可以解决问题：

SELECT emp.Name, NVL(IntAmount,0), NVL(ExtAmount,0)
FROM Employees emp
  LEFT JOIN
    (SELECT EmployeeID, sum(Amount) as IntAmount
     FROM InternalCosts GROUP BY EmployeeID) int
    ON emp.EmployeeID = int.EmployeeID
  LEFT JOIN
    (SELECT EmployeeID, sum(Amount) as ExtAmount
     FROM ExternalCosts GROUP BY EmployeeID) ext
    ON emp.EmployeeID = ext.EmployeeID

还请注意，在这种情况下以及将来可能对您的表结构进行规范化可能会对您有所帮助（我的意思是将外部成本和内部成本合并到一个表中，前提是当然可以）。

Answer 4

我建议您改为使用 Employee ID 尝试一个组，然后再进行 INNER 联接以投影 Employee 表中的名称。

干杯！

Answer 5

试试这个

SELECT t1.emp_name,inernalAmount,sum(ext.Amount) as externalAmount from
(
SELECT emp.EmployeeID,emp.Name, sum(int.Amount) as internalAmount 
FROM Employees emp inner join InternalCosts int on emp.EmployeeId = int.EmployeeID
) t1 inner join ExternalCosts ext on t1.EmployeeID = ext.EmployeeID
GROUP BY t1.Name,internalAmount