+---------------+     +---------------+
| PRODUCTS      |-----< PRODUCT_SKUS  |
+---------------+     +---------------+
| #product_id   |     | #product_id   |
|  product_name |     | #sku_id       |
+---------------+     |  sku          |
        |             |  price        |
        |             +---------------+
        |                     |
+-------^-------+      +------^------+
| OPTIONS       |------< SKU_VALUES  |
+---------------+      +-------------+
| #product_id   |      | #product_id |
| #option_id    |      | #sku_id     |
|  option_name  |      | #option_id  |
+---------------+      |  value_id   |
        |              +------v------+
+-------^-------+             |
| OPTION_VALUES |-------------+
+---------------+
| #product_id   |
| #option_id    |
| #value_id     |
|  value_name   |
+---------------+