WITH RECURSIVE po (DEPT_NO, DEPARTMENT) AS (
-- Находим отдел, которым напрямую руководит Роберт Нельсон
SELECT D.DEPT_NO, D.DEPARTMENT
FROM DEPARTMENT D
INNER JOIN EMPLOYEE E ON D.MNGR_NO = E.EMP_NO
WHERE E.FIRST_NAME = 'Robert' AND E.LAST_NAME = 'Nelson'
UNION ALL
-- Рекурсивно находим подчиненные отделы
SELECT D.DEPT_NO, D.DEPARTMENT
FROM DEPARTMENT D
INNER JOIN po ON D.HEAD_DEPT = po.DEPT_NO
)
SELECT DEPARTMENT
FROM po