获取MySQL数据库中按字段分组的最高值的行

I have the following table

我有下表

+----+----------+-----+
| id | priority | sub |
+----+----------+-----+
| 1  |    1     |  A  |
| 2  |    3     |  A  |
| 3  |    4     |  A  |
| 4  |    2     |  B  |
| 5  |    9     |  B  |
+----+----------+-----+
+----+-----