```mermaid erDiagram CUSTOMER { int id PK string name string email } ORDER { int id PK int customerId FK date orderDate float totalAmount } PRODUCT { int id PK string name float price } ORDER_ITEM { int id PK int orderId FK int productId FK int quantity float price } CUSTOMER ||--o{ ORDER : places ORDER ||--o{ ORDER_ITEM : includes PRODUCT ||--o{ ORDER_ITEM : is part of ```