与上题相同 找出当前薪水第二多的员工 先找出最高薪水

select max(salary) from salaries

然后再进行判断不是最高薪水 筛选后的最高薪水就是地第二高的薪水

select max(salary) from salaries where salary<>(select max(salary) from salaries)

最后判断等于第二高薪水

select emp_no,salary,last_name,first_name 
    from employees join salaries using(emp_no)
    where salary =(select max(salary) from salaries where salary<>(select max(salary) from salaries))