Table 1:
+---+
| 1 |
+---+
| 2 |
+---+
| 3 |
+---+
| 4 |
+---+


Table 2:
+---+---+
| 1 | 4 |
+---+---+
| 2 | 1 |
+---+---+
| 3 | 4 |
+---+---+
| 4 | 1 |
+---+---+
| 5 | 1 |
+---+---+
| 6 | 1 |
+---+---+
| 7 | 2 |
+---+---+
| 8 | 4 |
+---+---+
| 9 | 2 |
+---+---+
|10 | 3 |
+---+---+
|11 | 4 |
+---+---+
|12 | 3 |
+---+---+
|13 | 3 |
+---+---+
|14 | 3 |
+---+---+
|15 | 4 |
+---+---+
|16 | 2 |
+---+---+

Result:
+---+---------------------+
| 1 |  2,  4,  5,  6      |
+---+---------------------+
| 2 |  7,  9, 16          |
+---+---------------------+
| 3 | 10, 12, 13, 14      |
+---+---------------------+
| 4 |  1,  3,  8, 11, 15  |
+---+---------------------+