陈忠诚 多表查询

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

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 JOIN departments d
ON e.department_id = d.department_id
JOIN locations l
ON d.location_id = 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 LEFT 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;