把标题长度限制那么短干啥！！！！
查找所有员工的last_name和first_name以及对应的dept_name
https://www.nowcoder.com/practice/5a7975fabe1146329cee4f670c27ad55
select last_name,
first_name,
dept_name
from employees
left join dept_emp using(emp_no)
left join departments using(dept_no)
