Online shopping system ER diagram modeling customer, order, payment, product, and supplier entities with normalized relationships. Customers create orders and maintain shopping carts; orders link to payments and order items; products are sourced from suppliers and appear in both carts and orders. This schema demonstrates proper normalization with primary and foreign keys, separating transactional (Order, Payment) from catalog (Product, Supplier) and session (Cart) concerns. The design supports concurrent shopping, inventory tracking, and payment reconciliation—critical for scalable e-commerce platforms. Fork this diagram on Diagrams.so to customize for your database implementation, add indexes, or extend with reviews and wishlist entities.