재귀 (추후삭제)

WITH EmployeeHierarchy (employee_id, manager_id, employee_name, level) AS
(
    SELECT employee_id, manager_id, employee_name, 0 as level
    FROM employees
    WHERE manager_id IS NULL

    UNION ALL

    SELECT e.employee_id, e.manager_id, e.employee_name, eh.level + 1
    FROM employees e
    INNER JOIN EmployeeHierarchy eh
    ON e.manager_id = eh.employee_id
)
SELECT employee_id, manager_id, employee_name, level
FROM EmployeeHierarchy;

 

 

위의 예시에서 

(employee_id, manager_id, employee_name, level)
값 은 첫번째 SELECT 값을 저장하는것.