使用窗口函数,答案正确

select distinct emp_no,(first_value(salary) over w- last_value(salary) over w)as growth
from salaries s
where emp_no in (select distinct emp_no from salaries where to_date='9999-01-01')
WINDOW w as (
partition by emp_no order by to_date desc ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
);