+------+-----------------+
| :sid | :supplying      |
+------+-----------------+
| S1   | +------+------+ |
|      | | :pid | :qty | |
|      | +------+------+ |
|      | | P1   |  300 | |
|      | | P2   |  200 | |
|      | | P3   |  400 | |
|      | | P4   |  200 | |
|      | | P5   |  100 | |
|      | | P6   |  100 | |
|      | +------+------+ |
| S2   | +------+------+ |
|      | | :pid | :qty | |
|      | +------+------+ |
|      | | P1   |  300 | |
|      | | P2   |  400 | |
|      | +------+------+ |
| S3   | +------+------+ |
|      | | :pid | :qty | |
|      | +------+------+ |
|      | | P2   |  200 | |
|      | +------+------+ |
| S4   | +------+------+ |
|      | | :pid | :qty | |
|      | +------+------+ |
|      | | P2   |  200 | |
|      | | P4   |  300 | |
|      | | P5   |  400 | |
|      | +------+------+ |
+------+-----------------+