王姜坤 多表查询

SELECT e.employee_id,d.department_name
FROM employees e,departments d
WHERE e.department_id = d.department_id;

SELECT * FROM employees;

#mysql不支持sql92的外连接

SELECT employee_id,department_name
FROM employees e JOIN departments d
ON e.department_id = d.department_id;

SELECT employee_id,department_name
FROM employees e INNER JOIN departments d
ON e.department_id = d.department_id;

SELECT employee_id,department_name FROM departments,employees WHERE employees.department_id=departments.department_id(+);
#
SELECT employee_id,department_name,city
FROM employees e JOIN departments d
ON e.department_id = d.department_id
JOIN locations l ON l.location_id;


SELECT employee_id,department_name
FROM employees e LEFT OUTER JOIN departments d
ON e.department_id = d.department_id;

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