scores表
+----+-------+
| Id | Score |
+----+-------+
| 1 | 3.50 |
| 2 | 3.65 |
| 3 | 4.00 |
| 4 | 3.85 |
| 5 | 4.00 |
| 6 | 3.65 |
+----+-------+
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按照分数排名
+-------+------+
| Score | Rank |
+-------+------+
| 4.00 | 1 |
| 4.00 | 1 |
| 3.85 | 2 |
| 3.65 | 3 |
| 3.65 | 3 |
| 3.50 | 4 |
+-------+------+
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1：思路
首先定义 初始排名的值的0, 然后 查询的每一条数据 @rank这个变量就会+1。
这就是一个比较简单的排名， 但是你会发现 score数值一样的话，排名应该是一样的，因此这个并不正确。
mysql> set @rank = 0;
mysql> select score, (@rank := @rank + 1) as rank from scores order by score desc;
+-------+------+
| score | rank |
+-------+------+
| 4.00 | 1 |
| 4.00 | 2 |
| 3.85 | 3 |
| 3.65 | 4 |
| 3.65 | 5 |
| 3.50 | 6 |
+-------+------+
6 rows in set (0.00 sec)
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2：比较前一个数值
mysql> set @rank = 0;
Query OK, 0 rows affected (0.00 sec)mysql> set @prev = null;
Query OK, 0 rows affected (0.00 sec)
mysql> select score, if (@prev = score, @rank ,@rank := @rank + 1 ) as Rank , (@prev := score) as tmp from scores order by score desc;
+——-+——+——+
| score | Rank | tmp |
+——-+——+——+
| 4.00 | 1 | 4.00 |
| 4.00 | 1 | 4.00 |
| 3.85 | 2 | 3.85 |
| 3.65 | 3 | 3.65 |
| 3.65 | 3 | 3.65 |
| 3.50 | 4 | 3.50 |
+——-+——+——+
6 rows in set (0.00 sec)
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