mysql分组排序并获得排序号码

数据表 grades：

需要得到查询结果：

sql语句：

 select *, (select count(1) + 1  from grades B  where A.gender = B.gender and A.grade < B.grade) as rank from grades A order by gender , grade desc;
 
 参见：

http://topic.youkuaiyun.com/u/20110411/10/a303ad9d-d061-4781-952f-7de9897f0bed.html