8일차 # 5-23: LEFT OUTER JOIN

  SELECT e.last_name, e.department_id, d.department_name

  FROM   employees e LEFT OUTER JOIN departments d

  ON   (e.department_id = d.department_id) ;

  SELECT e.last_name, e.department_id, d.department_name

  FROM   employees e JOIN departments d

  ON   (e.department_id = d.department_id) ;

     ==> 위의 OUTER JOIN과 출력결과를 비교해 보세요.

      ↓ ↓

  <Oracle Syntax> ==> outer join할 때는 (+) 기호를 WHERE 조건에 사용합니다.

  SELECT e.last_name, e.department_id, d.department_name

  FROM   employees e, departments d

  WHERE  e.department_id = d.department_id (+);