Master-Detail Relationships
Most many-to-one relationships also define master-detail relationships. In a master-detail relationship, a record in one entity defines the main body of the data and one or more records in another entity provide additional detail. In Figure 2.3, the CustomerOrders record defines the main body of data. For each CustomerOrders record, one or more OrderItems records provide additional detail.
The master-detail relationship is conceptual and does not automatically apply to all many-to-one relationships in the same way. For instance, the relationship between OrderItems records and Inventory records is in some sense the opposite of the relationship between CustomerOrders records and OrderItems records. You can think of ...
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