Mysql 数据分组取某字段值所有最大的记录行_MySQL

需求：

表中同一个uid（用户）拥有多条游戏等级记录，现需要取所有用户最高等级（level）的那一条数据，且时间（time）越早排越前。这是典型的排名表

+------+-------+--------------+---------------------+| uid  | level | role         | time                |+------+-------+--------------+---------------------+| 7    |     1 | 摇滚圣魔     | 2014-06-12 15:01:05 || 1134 |     4 | 唯我独尊     | 2014-06-12 15:02:38 || 1134 |     4 | 唯我独尊     | 2014-06-12 15:02:39 || 7    |     3 | 摇滚圣魔     | 2014-06-12 15:02:59 || 5    |     3 | 韵儿铃♦      | 2014-06-12 15:04:09 || 7363 |     6 | 诗荷冰月     | 2014-06-12 15:04:23 || 6684 |     4 | つ道远虚空つ | 2014-06-12 15:05:13 || 7    |    16 | 摇滚圣魔     | 2014-06-12 15:05:46 || 1    |     2 | 斗土豪       | 2014-06-12 15:05:48 || 7    |    26 | 摇滚圣魔     | 2014-06-12 15:08:36 || 6684 |     8 | つ道远虚空つ | 2014-06-12 15:08:45 || 5    |    12 | 韵儿铃♦      | 2014-06-12 15:09:47 || 6834 |     1 | 无敌追翼     | 2014-06-12 15:10:56 || 5    |    16 | 韵儿铃♦      | 2014-06-12 15:11:18 || 8719 |     1 | 君望赤       | 2014-06-12 15:11:48 || 6274 |    36 | 五月独孤     | 2014-06-12 15:12:22 || 8724 |    26 | 童童         | 2014-06-12 15:12:31 || 1134 |    32 | 唯我独尊     | 2014-06-12 15:12:51 || 7    |    26 | 摇滚圣魔     | 2014-06-12 15:13:38 || 5    |    25 | 韵儿铃♦      | 2014-06-12 15:14:48 || 7757 |     3 | つ清灵旋つ   | 2014-06-12 15:16:50 || 7    |    26 | 摇滚圣魔     | 2014-06-12 15:17:26 || 5    |    28 | 韵儿铃♦      | 2014-06-12 15:18:08 || 7757 |    23 | つ清灵旋つ   | 2014-06-12 15:19:29 || 6274 |    43 | 五月独孤     | 2014-06-12 15:19:54 || 8724 |    30 | 童童         | 2014-06-12 15:20:39 || 7757 |    26 | つ清灵旋つ   | 2014-06-12 15:20:58 || 8707 |    36 | 就是干       | 2014-06-12 15:22:28 || 7757 |    29 | つ清灵旋つ   | 2014-06-12 15:23:05 || 7757 |    32 | つ清灵旋つ   | 2014-06-12 15:24:57 || 8726 |    10 | 连曦         | 2014-06-12 15:26:01 || 7363 |    34 | 诗荷冰月     | 2014-06-12 15:26:58 || 7    |    26 | 摇滚圣魔     | 2014-06-12 15:27:33 || 5    |    37 | 韵儿铃♦      | 2014-06-12 15:27:37 || 8347 |     1 | 无敌         | 2014-06-12 15:28:09 || 6274 |    47 | 五月独孤     | 2014-06-12 15:28:13 || 1    |    32 | 斗土豪       | 2014-06-12 15:29:18 || 1134 |    46 | 唯我独尊     | 2014-06-12 15:30:52 || 7757 |    41 | つ清灵旋つ   | 2014-06-12 15:30:56 || 9    |    34 | 饭饭饭饭の   | 2014-06-12 15:31:03 || 6274 |    48 | 五月独孤     | 2014-06-12 15:31:18 || 8724 |    41 | 童童         | 2014-06-12 15:32:30 || 7757 |    42 | つ清灵旋つ   | 2014-06-12 15:34:24 || 1134 |    48 | 唯我独尊     | 2014-06-12 15:34:56 || 1100 |     2 | 圣魔霄       | 2014-06-12 15:35:54 || 1008 |    21 | ∵嘟嘟冰儿∵ | 2014-06-12 15:36:10 || 7757 |    45 | つ清灵旋つ   | 2014-06-12 15:40:49 || 3088 |     4 | 战魂凌空    | 2014-06-12 15:41:38 || 5    |    41 | 韵儿铃♦      | 2014-06-12 15:41:56 || 7757 |    46 | つ清灵旋つ   | 2014-06-12 15:43:24 |

实现过程：

1.首先对该数据进行2次排序，uid 排序以及等级的降序排序

2.对排序后的结果用uid进行分组,分组后等级降序排序,时间升序排序

实现SQL:

select * from (select a.uid,a.level,a.role,a.time from 数据表 a where order BY a.uid desc,a.level desc) as 别名 group by user_uid order by level desc,time asc limit 30;