这是我的数据表:
| uid | date | visit | transactionDate |
+-----+----------+-------+-----------------+
| 1 | 6/2/2014 | 1 | 6/9/2014 |
| 1 | 6/2/2014 | 1 | 8/4/2014 |
| 2 | 6/2/2014 | 1 | 8/2/2014 |
| 2 | 6/2/2014 | 1 | 10/17/2014 |
| 2 | 6/2/2014 | 1 | 10/20/2014 |
| 3 | 6/2/2014 | 1 | 6/9/2014 |
| 3 | 6/2/2014 | 1 | 6/10/2014 |
| 3 | 6/2/2014 | 1 …