mysql怎么把两张表

+----+-----------+---------+--------+
| id | name      | salary  | dept_id|
+----+-----------+---------+--------+
|  1 | John Doe  |  50000  |   1    |
|  2 | Jane Smith|  60000  |   2    |
|  3 | Mike Brown|  55000  |   1    |
+----+-----------+---------+--------+

+----+-----------+
| id | name      |
+----+-----------+
|  1 | HR        |
|  2 | IT        |
+----+-----------+

SELECT employees.name AS employee_name, departments.name AS department_name
FROM employees
INNER JOIN departments ON employees.dept_id = departments.id;

+---------------+----------------+
| employee_name | department_name|
+---------------+----------------+
| John Doe      | HR             |
| Jane Smith    | IT             |
| Mike Brown    | HR             |
+---------------+----------------+

SELECT employees.name AS name, departments.name AS department_name
FROM employees
LEFT JOIN departments ON employees.dept_id = departments.id
UNION
SELECT employees.name AS name, departments.name AS department_name
FROM employees
RIGHT JOIN departments ON employees.dept_id = departments.id;