178.分数排名

179. 编写一个 SQL 查询来实现分数排名。如果两个分数相同，则两个分数排名（Rank）相同。
180. 请注意，平分后的下一个名次应该是下一个连续的整数值。
181. 换句话说，名次之间不应该有“间隔”。

+----+-------+
| Id | Score |
+----+-------+
| 1  | 3.50  |
| 2  | 3.65  |
| 3  | 4.00  |
| 4  | 3.85  |
| 5  | 4.00  |
| 6  | 3.65  |
+----+-------+
例如，根据上述给定的 Scores 表，你的查询应该返回（按分数从高到低排列）：

+-------+------+
| Score | Rank |
+-------+------+
| 4.00  | 1    |
| 4.00  | 1    |
| 3.85  | 2    |
| 3.65  | 3    |
| 3.65  | 3    |
| 3.50  | 4    |
+-------+------+


select a.Score ,(select count(distinct b.Score) 
from Scores b where b.Score>=a.Score) as Rank
from Scores a order by Score desc

或
# Write your MySQL query statement below
select Score ,Rank from (select Score,@CUR:=IF(@PREV=Score,@CUR+0,@CUR:=@CUR+1) as Rank,
@PREV:=Score from Scores,(select @CUR:=0,@PREV:=NULL) r ORDER by Score desc) s