Entity Relationship

ER Diagram

```mermaid
erDiagram
          CUSTOMER }|..|{ DELIVERY-ADDRESS : has
          CUSTOMER ||--o{ ORDER : places
          CUSTOMER ||--o{ INVOICE : "liable for"
          DELIVERY-ADDRESS ||--o{ ORDER : receives
          INVOICE ||--|{ ORDER : covers
          ORDER ||--|{ ORDER-ITEM : includes
          PRODUCT-CATEGORY ||--|{ PRODUCT : contains
          PRODUCT ||--o{ ORDER-ITEM : "ordered in"
```

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