oracle – 外串連

左：SELECT e.last_name, e.department_id, d.department_name  FROM employees e  LEFT  JOIN departments d  ON (e.department_id = d.department_id); 

等價於

SELECT e.last_name, e.department_id, d.department_name  FROM employees e, departments d  WHERE e.department_id=d.department_id(+);   右：SELECT e.last_name, e.department_id, d.department_name  FROM employees e  RIGHT JOIN departments d  ON (e.department_id = d.department_id); 

等價於

SELECT e.last_name, e.department_id, d.department_name  FROM employees e, departments d  WHERE e.department_id(+)=d.department_id;   全外串連：SELECT e.last_name, e.department_id, d.department_name  FROM employees e  FULL  JOIN departments d  ON (e.department_id = d.department_id); 等價於SELECT e.last_name, e.department_id, d.department_name  FROM employees e, departments d  WHERE e.department_id(+)=d.department_id(+);