[打卡]段泽欣 。多表查询

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 JOIN departments d
ON e.department_id = d.department_id;

SELECT employee_id,department_name
FROM employees e FULL OUTER 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;

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 LEFT JOIN departments d
ON e.department_id = d.department_id;

SELECT employee_id,department_name
FROM employees e RIGHT 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
WHERE d.department_id IS NULL;

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



SELECT employee_id,department_name
FROM employees e LEFT JOIN departments d
ON e.department_id = d.department_id
UNION ALL
SELECT employee_id, department_name
FROM employees e RIGHT JOIN departments d
ON e.department_id = d.department_id
WHERE d.department_id IS NULL;


SELECT employee_id,department_name
FROM employees e RIGHT JOIN departments d
ON e.department_id = d.department_id
UNION ALL
SELECT employee_id, department_name
FROM employees e LEFT JOIN departments d
ON e.department_id = d.department_id
WHERE d.department_id IS NULL;




SELECT employee_id, department_name
FROM employees e LEFT JOIN departments d
ON e.department_id = d.department_id
WHERE d.department_id IS NULL
UNION
SELECT employee_id, department_name
FROM employees e RIGHT JOIN departments d
ON e.department_id = d.department_id
WHERE d.department_id IS NULL;