CREATE TABLE computers (serial_number,  manufacturer, model) AS
SELECT 'D123',  'Dell', 'laptop' FROM DUAL UNION ALL
SELECT 'D124',  'Dell', 'laptop' FROM DUAL UNION ALL
SELECT 'A1424',  'Apple', 'laptop' FROM DUAL UNION ALL
SELECT 'A1425',  'Apple', 'laptop' FROM DUAL UNION ALL
SELECT 'C1725',  'compaq', 'tower' FROM DUAL UNION ALL
SELECT 'C1726',  'compaq', 'tower' FROM DUAL UNION ALL
SELECT 'C1727',  'compaq', 'tower' FROM DUAL;


CREATE TABLE employees (employee_id, manager_id, first_name, last_name, serial_number) AS
SELECT 1, NULL, 'Alice', 'Abbot', 'D123' FROM DUAL UNION ALL
SELECT 2, 1, 'Beryl', 'Baron','D124' FROM DUAL UNION ALL
SELECT 3, 1, 'Carol', 'Chase','A1424' FROM DUAL UNION ALL
SELECT 4, 2, 'Debra', 'Doris','A1425' FROM DUAL UNION ALL
SELECT 5, 3, 'Emily', 'Evans','C1725' FROM DUAL UNION ALL
SELECT 6, 3, 'Fiona', 'Frank','C1726' FROM DUAL UNION ALL
SELECT 7, 6, 'Gemma', 'Grace','C1727' FROM DUAL;

select 
EMP.EMPLOYEE_ID,
EMP.FIRST_NAME,    EMP.LAST_NAME,
EMP.MANAGER_ID,
M.FIRST_NAME,    M.LAST_NAME
  from 
 employees emp
  LEFT OUTER JOIN employees m ON
emp.MANAGER_ID
 = m.EMPLOYEE_ID
ORDER BY EMP.EMPLOYEE_ID;

SQL> select
  2  EMP.EMPLOYEE_ID,
  3  EMP.FIRST_NAME,    EMP.LAST_NAME,
  4  EMP.MANAGER_ID,
  5  M.FIRST_NAME,    M.LAST_NAME,
  6  EMP.serial_number,
  7  C.manufacturer,
  8  C.model
  9    from
 10   employees emp
 11   JOIN computers c ON emp.serial_number = c.serial_number
 12   LEFT OUTER JOIN employees m ON emp.MANAGER_ID = m.EMPLOYEE_ID
 13  ORDER BY EMP.EMPLOYEE_ID;
EMPLOYEE_ID FIRST LAST_ MANAGER_ID FIRST LAST_ SERIA MANUFA MODEL
----------- ----- ----- ---------- ----- ----- ----- ------ ------
          1 Alice Abbot                        D123  Dell   laptop
          2 Beryl Baron          1 Alice Abbot D124  Dell   laptop
          3 Carol Chase          1 Alice Abbot A1424 Apple  laptop
          4 Debra Doris          2 Beryl Baron A1425 Apple  laptop
          5 Emily Evans          3 Carol Chase C1725 compaq tower
          6 Fiona Frank          3 Carol Chase C1726 compaq tower
          7 Gemma Grace          6 Fiona Frank C1727 compaq tower