Problem:
Write a SQL query to rank scores. If there is a tie between two scores, both should have the same ranking. Note that after a tie, the next ranking number should be the next consecutive integer value. In other words, there should be no “holes” between ranks.

+----+-------+
| Id | Score |
+----+-------+
| 1  | 3.50  |
| 2  | 3.65  |
| 3  | 4.00  |
| 4  | 3.85  |
| 5  | 4.00  |
| 6  | 3.65  |
+----+-------+
For example, given the above `Scores` table, your query should generate the following report (order by highest score):
+-------+------+
| Score | Rank |
+-------+------+
| 4.00  | 1    |
| 4.00  | 1    |
| 3.85  | 2    |
| 3.65  | 3    |
| 3.65  | 3    |
| 3.50  | 4    |
+-------+------+

Solution: 定义一个变量row_num保存排名,初始化为0,从dual表中取值,对分数进行将序排列,排名升序。SQL语句如下:

1
2
3
4
5
select s.Score, t.Rank
from ( select @row_num:[email protected]_num + 1 Rank, Score
from ( select Score
from Scores group by Score desc ) t1 join ( select @row_num := 0
from dual) t2) t, Scores s where s.Score=t.Score group by Score desc, Rank asc, Id;