select dept_no,emp_no,salaryfrom (select dept_no,de.emp_no,salary,rank()over(partition by dept_no order by salary desc) 排名 from dept_emp de inner join salaries sa on de.emp_no = sa.emp_no ) as rkwhere 排名=1order by dept_no#每个表格后面两列from_date有什么用?没有使用这两列也通过了