先找到最大薪水

select max(salary) from salaries where to_date = '9999-01-01' 

然后将上面的结果作为一个条件，查找第二大！

select max(salary) from salaries where to_date = '9999-01-01' and salary < (select max(salary) from salaries where to_date = '9999-01-01') 

最后联结两个表就可以得到想要的结果！

SELECT a.emp_no, b.salary,a.last_name,a.first_name from employees a inner join salaries b 
on a.emp_no = b.emp_no
where to_date = '9999-01-01' 
and b.salary = 
(
    select max(salary) from salaries where to_date = '9999-01-01' 
    and salary < (select max(salary) from salaries where to_date = '9999-01-01')
)