获取当前薪水第二多的员工以及其对应的薪水salary
获取当前薪水第二多的员工的emp_no以及其对应的薪水salary
https://www.nowcoder.com/practice/8d2c290cc4e24403b98ca82ce45d04db
select emp_no,salary from salaries where salary=(select salary from salaries group by salary order by salary desc limit 1,1)