對所有員工的當前薪水按照salary進行按照1-N的排名

題目描述
對所有員工的當前(to_date=‘9999-01-01’)薪水按照salary進行按照1-N的排名，相同salary並列且按照emp_no升序排列
CREATE TABLE salaries (
emp_no int(11) NOT NULL,
salary int(11) NOT NULL,
from_date date NOT NULL,
to_date date NOT NULL,
PRIMARY KEY (emp_no,from_date));

解題思路：

代碼

select a.emp_no,a.salary,count(distinct b.salary) rank
from salaries as a, salaries as b
where a.salary <= b.salary and a.to_date = '9999-01-01' and b.to_date = '9999-01-01'
group by a.emp_no order by rank;

輸出描述：