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| A_ID | A_N | B_ID | B_N |
|---|---|---|---|
| 1 | 101 | 1 | 101 |
| 1 | 101 | 2 | 101 |
| 2 | 101 | 1 | 101 |
| 2 | 101 | 2 | 101 |
| 3 | 102 | null | null |
| 4 | 102 | null | null |
| A_ID | A_N | B_ID | B_N |
|---|---|---|---|
| 1 | 101 | 1 | 101 |
| 1 | 101 | 2 | 101 |
| 2 | 101 | 2 | 101 |
| 2 | 101 | 1 | 101 |
| 3 | 102 | null | null |
| 4 | 102 | null | null |