How to SUM rows with an outer join? - sql

Question

Question:
I have the following tables that I'd like to sum on two fields: HOURS and RATE. I also want to retrieve the NAME from the third table, joining all 3 tables on the field LINE_NUM.
If the LINE_NUM and CODE are the same, sum the fields of A with B.
Table EARNINGS A:
| EMPLOYEE_ID | LINE_NUM | REG_CODE | REG_HOURS | REG_RATE |
------------------------------------------------------------
| 0001 | 1 | C | 20 | 200 |
| 0002 | 1 | H | 0 | 0 |
Table OTH_EARNINGS B:
| LINE_NUM | OTH_CODE | OTH_HOURS | OTH_RATE |
----------------------------------------------
| 1 | A | 0 | 0 |
| 1 | B | 0 | 0 |
| 1 | C | 10 | 100 |
| 2 | A | 50 | 50 |
Table PAYCHECK C:
| EMPLOYEE_ID | LINE_NUM | NAME |
---------------------------------
| 0001 | 1 | Tom |
| 0001 | 2 | Tom |
| 0002 | 1 | John |
The result I'm looking for should be:
| EMPLOYEE_ID | LINE_NUM | CODE | HOURS | RATE | NAME |
-------------------------------------------------------
| 0001 | 1 | A | 0 | 0 | Tom |
| 0001 | 1 | B | 0 | 0 | Tom |
| 0001 | 1 | C | 30 | 300 | Tom |
| 0001 | 2 | A | 50 | 50 | Tom |
| 0002 | 1 | H | 0 | 0 | John |
Any idea how I can achieve this?
What I tried:
I've tried (table A with C) UNION (table B with C), but I can't get the sums to work.
SELECT C.EMPLOYEE_ID, A.REG_CODE, A.REG_HRS, SUM(A.REG_RATE)
FROM EARNINGS A, PAYCHECK C
WHERE A.LINE_NUM = C.LINE_NUM
GROUP BY C.EMPLOYEE_ID, A.REG_CODE, A.REG_HRS
UNION
SELECT D.EMPLOYEE_ID, B.OTH_CODE, B.OTH_HRS, SUM(B.OTH_RATE)
FROM OTH_EARNINGS B, PAYCHECK D
WHERE B.LINE_NUM = D.LINE_NUM
GROUP BY D.EMPLOYEE_ID, B.OTH_CODE, B.OTH_HRS
But I couldn't get the sum to work and it returned:
| EMPLOYEE_ID | LINE_NUM | CODE | HOURS | RATE | NAME |
-------------------------------------------------------
| 0001 | 1 | A | 0 | 0 | Tom |
| 0001 | 1 | B | 0 | 0 | Tom |
| 0001 | 1 | C | 10 | 100 | Tom |
| 0001 | 1 | C | 20 | 200 | Tom |
| 0001 | 2 | A | 50 | 50 | Tom |
| 0002 | 1 | H | 0 | 0 | John |

Answer 1

Your approach wasn't bad and you were almost there.
You should make the GROUP BY on the results of the 2 UNIONed queries being nested:
SELECT EMPLOYEE_ID, NAME, CODE, SUM(HRS), SUM(RATE)
FROM
(
SELECT C.EMPLOYEE_ID, C.NAME, A.REG_CODE AS CODE, A.REG_HRS AS HRS, A.REG_RATE AS RATE
FROM EARNINGS A
INNER JOIN PAYCHECK C ON A.LINE_NUM = C.LINE_NUM
UNION ALL
SELECT D.EMPLOYEE_ID, C.NAME, B.OTH_CODE AS CODE, B.OTH_HRS AS HRS, B.OTH_RATE AS RATE
FROM OTH_EARNINGS B
INNER JOIN PAYCHECK D ON B.LINE_NUM = D.LINE_NUM
)
GROUP BY EMPLOYEE_ID, NAME, CODE
However this will return wrong results because the JOINs on the PAYCHECK table will returns duplicates.
There's obviously something missing somewhere.
To identify the employee, you should combine 2 columns : EMPLOYEE_ID and LINE_NUM. For the first query on EARNING, there's no issue as the EMPLOYEE_ID is present in the table. However for the second query on OTH_EARNINGS, the EMPLOYEE_ID is missing...
In theory you should have something like this (check the INNER JOIN...ON)
SELECT EMPLOYEE_ID, NAME, CODE, SUM(HRS), SUM(RATE)
FROM
(
SELECT C.EMPLOYEE_ID, C.NAME, A.REG_CODE AS CODE, A.REG_HRS AS HRS, A.REG_RATE AS RATE
FROM EARNINGS A
INNER JOIN PAYCHECK C ON A.LINE_NUM = C.LINE_NUM AND A.EMPLOYEE_ID = C.EMPLOYEE_ID
UNION ALL
SELECT D.EMPLOYEE_ID, C.NAME, B.OTH_CODE AS CODE, B.OTH_HRS AS HRS, B.OTH_RATE AS RATE
FROM OTH_EARNINGS B
INNER JOIN PAYCHECK D ON B.LINE_NUM = D.LINE_NUM AND B.EMPLOYEE_ID = D.EMPLOYEE_ID
)
GROUP BY EMPLOYEE_ID, NAME, CODE
I also changed from your initial query:
the JOINs from implicit to explicit syntax.
the UNION into an UNION ALL as there's no reason here to remove the duplicates (maybe I am wrong)