获取部门当前manager的薪水状况

From 并列两表 + group by去重 + order by排序

select d.dept_no,d.emp_no,s.salary
from dept_manager as d,salaries as s
where d.emp_no = s.emp_no
and d.to_date = '9999-01-01'
and s.to_date = '9999-01-01'
group by salary
order by d.dept_no asc;

也可以使用内连接

select d.dept_no,d.emp_no,s.salary
from dept_manager as d inner join salaries as s
on d.emp_no = s.emp_no
where d.to_date = '9999-01-01'
and s.to_date = '9999-01-01'
group by salary
order by d.dept_no asc;