Consider a double N: N relationship, exemplified by a product hierarchy, where the smallest element, for example the screw, is composed of the same screw.

The database model has a single table, where the components are also Products: products (Product id -> Product data, component, quantity).

Q: Define the table structure and insert the necessary data that represent the following product and, express in SQL a query that returns the leaves of the product tree, i.e., the set (F, G, E, C).

PRODUCT compound n component n COMPOSITION A B D E F G