Combine the result of one sql query into another - sql

Question

I have the below table.
CREATE TABLE Employee_id_credits ( Employee_id, credits ) AS
SELECT 10, 1 FROM DUAL UNION ALL
SELECT 12, 1 FROM DUAL UNION ALL
SELECT 10, 1 FROM DUAL UNION ALL
SELECT 12, 1 FROM DUAL UNION ALL
SELECT 12, 1 FROM DUAL UNION ALL
SELECT 14, 1 FROM DUAL;
The below query groups and counts the total number of credits for employees.
select Employee_id, count(*) as "Total_credits"
from Employee_id_credits
group by Employee_id;
Gives the below output.
Employee_id Total_credits
----------- -------------
10 2
12 3
14 1
I have a Employee Manager table with the hierarchy.
CREATE TABLE Employee_Manager ( Employee_id, Manager_id ) AS
SELECT 10, 101 FROM DUAL UNION ALL
SELECT 12, 120 FROM DUAL UNION ALL
SELECT 13, 120 FROM DUAL UNION ALL
SELECT 14, 150 FROM DUAL UNION ALL
SELECT 101, NULL FROM DUAL UNION ALL
SELECT 120, 130 FROM DUAL UNION ALL
SELECT 130, NULL FROM DUAL;
I have a query to find the top level manager of the employee.
SELECT
Employee_id
FROM
Employee_Manager
WHERE
Manager_id is null
CONNECT BY PRIOR
Manager_id = Employee_id
START WITH
Employee_id = '12';
I want to combine the above two queries so that the output would look like below. How do I combine both queries?
Manager Total_credits
------- -------------
101 2
130 3
150 1

Answer 1

SQL Fiddle
Oracle 11g R2 Schema Setup:
CREATE TABLE Employee_id_credits ( Employee_id, credits ) AS
SELECT 10, 1 FROM DUAL UNION ALL
SELECT 12, 1 FROM DUAL UNION ALL
SELECT 10, 1 FROM DUAL UNION ALL
SELECT 12, 1 FROM DUAL UNION ALL
SELECT 12, 1 FROM DUAL UNION ALL
SELECT 14, 1 FROM DUAL;
CREATE TABLE Employee_Manager ( Employee_id, Manager_id ) AS
SELECT 10, 101 FROM DUAL UNION ALL
SELECT 12, 120 FROM DUAL UNION ALL
SELECT 13, 120 FROM DUAL UNION ALL
SELECT 14, 150 FROM DUAL UNION ALL
SELECT 101, NULL FROM DUAL UNION ALL
SELECT 120, 130 FROM DUAL UNION ALL
SELECT 130, NULL FROM DUAL;
Query 1 - Find the managers of each employee:
SELECT CONNECT_BY_ROOT( Employee_id ) AS Employee_id,
COALESCE( manager_id, employee_id ) AS manager_id
FROM Employee_manager
WHERE CONNECT_BY_ISLEAF = 1
CONNECT BY PRIOR Manager_id = Employee_id
Results:
| EMPLOYEE_ID | MANAGER_ID |
|-------------|------------|
| 10 | 101 |
| 12 | 130 |
| 13 | 130 |
| 14 | 150 |
| 101 | 101 |
| 120 | 130 |
| 130 | 130 |
Query 2 - Join that with the credits table and aggregate:
SELECT m.manager_id,
SUM( c.credits ) As total_credits
FROM Employee_id_credits c
INNER JOIN
(
SELECT CONNECT_BY_ROOT( Employee_id ) AS Employee_id,
COALESCE( manager_id, employee_id ) AS manager_id
FROM Employee_manager
WHERE CONNECT_BY_ISLEAF = 1
CONNECT BY PRIOR Manager_id = Employee_id
) m
ON ( c.employee_id = m.employee_id )
GROUP BY m.manager_id
Results:
| MANAGER_ID | TOTAL_CREDITS |
|------------|---------------|
| 101 | 2 |
| 130 | 3 |
| 150 | 1 |