改了好多次，感觉最简洁的一版
select s1.emp_no,s2.salary-s1.salary growth
from (select emp_no,salary
from salaries 
where (emp_no,to_date) 
in(select emp_no,min(to_date)
from salaries 
group by emp_no)) s1 join (select emp_no,salary
from salaries 
where to_date='9999-01-01') s2 on s1.emp_no=s2.emp_no
order by growth