窗口函数

select
t.emp_no
,(t.last_salary - t.first_salary) growth
from
(
select
emp_no
,first_value(salary) over(partition by emp_no order by from_date) first_salary
,last_value(salary) over(partition by emp_no order by from_date) last_salary
,last_value(to_date) over(partition by emp_no order by from_date) last_date
from salaries
) t
where t.last_date = '9999-01-01'
order by growth