请问用SAS怎么做到只保留配对的数据呢? 效果如下。感谢大家~~~!
| Origin_country | Code_prefix | | Origin_country | Code_prefix |
| 110 | 811 | | 110 | 811 |
| 110 | 811 | | 110 | 811 |
| 110 | 811 | | 110 | 811 |
| 304 | 811 | | 304 | 811 |
| 110 | 812 | | 110 | 813 |
| 110 | 813 | | 110 | 813 |
| 110 | 813 | | 110 | 813 |
| 110 | 813 | | 110 | 813 |
| 110 | 813 | | 110 | 813 |
| 110 | 813 | | 110 | 813 |
| 110 | 813 | | 304 | 813 |
| 304 | 813 | | 110 | 813 |
| 110 | 813 | | 304 | 813 |
| 304 | 813 | | 110 | 813 |
| 110 | 813 | | | |
| 110 | 814 | | | |
| 110 | 901 | | | |
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| 红色代表删除 |
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