[打卡]尹欣瑞 多表查询

#sql92 内连接
SELECT e.employee_id,d.department_name
FROM employees e,departments d
WHERE e.department_id=d.department_id;

SELECT * FROM employees;

#sql92 外连接 sql92不支持
SELECT e.employee_id,d.department_name
FROM employees e,departments d
WHERE e.department_id=d.department_id(+);

#sql99 内连接 INNER可省略
SELECT employee_id,department_name,city
FROM employees e JOIN departments d
ON e.department_id=d.department_id
JOIN locations l
ON d.location_id=l.location_id;

#左外连接 OUTER可省略
SELECT employee_id,department_name
FROM employees e LEFT OUTER JOIN departments d
ON e.department_id=d.department_id;

#右外连接
SELECT employee_id,department_name
FROM employees e RIGHT OUTER JOIN departments d
ON e.department_id=d.department_id;