题解 | 查找所有员工的last_name和first_name以及对应的dept_name

select  C.last_name,C.first_name, D.dept_name
from 
(
    select A.last_name,A.first_name,B.dept_no
    from employees A
    left join dept_emp B
    on A.emp_no = B.emp_no
) as C

left join departments D
on C.dept_no = D.dept_no