我有一个如下表:
+----+-----+-----+
| ID | GRP | NR |
+----+-----+-----+
| 1 | 1 | 101 |
| 2 | 1 | 102 |
| 3 | 1 | 103 |
| 4 | 1 | 105 |
| 5 | 1-2 | 106 |
| 6 | 1-2 | 109 |
| 7 | 1-2 | 110 |
| 8 | 2 | 201 |
| 9 | 2 | 202 |
| 10 | 3 | 300 | …