查找所有员工的信息
查找所有员工的last_name和first_name以及对应部门编号dept_no
https://www.nowcoder.com/practice/dbfafafb2ee2482aa390645abd4463bf
SELECT
e.last_name,
e.first_name,
d.dept_no
FROM
employees AS e
LEFT JOIN dept_emp AS d ON d.emp_no = e.emp_no;