#思路：表中先剔除最大薪水，再选出该表内的最大薪水，再做个子查询即可。
select emp_no, salary, last_name, first_name
from salaries left join employees using(emp_no)
where salary in (
select max(salary) 
from
(select salary from salaries
where salary not in (select max(salary) from salaries where to_date='9999-01-01') and to_date='9999-01-01') as tb1)