erDiagram USER ||--o{ ORDER : places USER { int id PK string username string email string password_hash date created_at } PRODUCT ||--o{ ORDER_ITEM : "contained in" PRODUCT { int id PK string name text description decimal price int stock int category_id FK } ORDER ||--|{ ORDER_ITEM : contains ORDER { int id PK int user_id FK date order_date string status decimal total_amount } CATEGORY ||--o{ PRODUCT : has CATEGORY { int id PK string name text description } ORDER_ITEM { int id PK int order_id FK int product_id FK int quantity decimal unit_price }