取两次最大值后就是第二大的

select r1.emp_no,r1.salary,r1.last_name,r1.first_name
from(
select e.*,s.salary
from employees e
inner join salaries s
on e.emp_no=s.emp_no) r1
where r1.salary = (
select max(salary) from salaries where salary != (
select max(salary) from salaries
)
)