问题：已知存在一张工资表，请查询出每个员工的工号、工资、排名
解答：select s1.emp_no,s1.salary,(count(distinct s2.salary)) as rank
from salaries as s1,salaries as s2
where s1.to_date="9999-01-01"
and s2.to_date="9999-01-01"
and s1.salary<=s2.salary
group by s1.emp_no
order by s1.salary desc,s1.emp_no asc