The model evolved from the file systems that the databases replaced

3. Use the order ID to find the corresponding line items in the Order Detail file.

4. For each line item, use the product ID to find the corresponding product name in the Product file.

The Hierarchical Model

The earliest databases followed the hierarchical model. The model evolved from the file systems that the databases replaced, with records arranged in a hierarchy much like an organization chart. Each file from the flat file system became a record type, or

Figure 1-3 Hierarchical model structure for Northwind