The scenario
A multi-branch bookstore chain needs centralized purchasing to negotiate supplier discounts while each branch manages local inventory and customer orders. This ERD models branch, supplier, purchase order, inventory, customer, and order entities with their relationships.
What is in this drawing
Read the decisions behind it.
01
Composite keys for BookAuthor and Inventory capture many-to-many relationships
02
PurchaseOrder is linked to Branch and Supplier to centralize procurement
03
Order and OrderLine separate order header from line items for sales
Use this pattern for retail or multi-location inventory systems that centralize procurement but decentralize sales and stock.
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