https://www.nowcoder.com/practice/5a7975fabe1146329cee4f670c27ad55?tpId=82&tags=&title=&difficulty=0&judgeStatus=0&rp=1

SELECT last_name, first_name, dept_name
FROM employees AS e LEFT JOIN (
    SELECT emp_no, dept_name
    FROM dept_emp de LEFT JOIN departments d
    ON de.dept_no = d.dept_no)k
ON e.emp_no = k.emp_no;