《数据库SQL实战》找出所有员工当前薪水salary情况

题目描述：找出所有员工当前(to_date=’9999-01-01’)具体的薪水salary情况，对于相同的薪水只显示一次,并按照逆序显示

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));

解析：关键字distinct去重，desc按照降序排列

select distinct(salary)
from salaries
where to_date=’9999-01-01’
order by salary desc