# 思想：一串数字，要判断某个数字的逆序排名，就统计这个数字小于这些数字及其本身的个数
# 注意：别忘了distinct 
# select s.emp_no,salary,last_name,first_name
# from salaries s
# inner join employees e
# on s.emp_no=e.emp_no
# where salary =(
#   select s1.salary
#   from salaries s1,salaries s2
#   where s1.salary<=s2.salary
#   group by s1.salary
#   having count(distinct s2.salary)=2
# )