START WITH CONNECT BY

SELECT A.EMPLOYEE_ID, A.FIRST_NAME, A.MANAGER_ID,

B.EMPLOYEE_ID, B.FIRST_NAME, B.MANAGER_ID

FROM EMPLOYEES A, EMPLOYEES B

WHERE A.MANAGER_ID = B.EMPLOYEE_ID;

SELECT A.EMPLOYEE_ID, A.FIRST_NAME, A.MANAGER_ID

FROM EMPLOYEES A

START WITH A.MANAGER_ID IS NOT NULL

CONNECT BY PRIOR A.MANAGER_ID = B.EMPLOYEE_ID;