How Can Object-Oriented Inheritance Be Modeled in a Relational Database?

Modeling Object-Oriented Inheritance in a Relational Database

When designing a data model, you may encounter situations where you need to represent object-oriented inheritance in a relational database scheme. One common scenario is when a table has fields related to the pricing of a product, which inherits specific attributes from the main product table.

To address this, renowned software architect Martin Fowler provides extensive guidance in his Patterns of Enterprise Application Architecture book. Here are three main inheritance mapping techniques discussed by Fowler:

1. Single Table Inheritance:

   • All subclasses and base class are stored in a single table.
   • A discriminator column indicates the subclass of each row.

2. Class Table Inheritance:

   • A base class table exists, and each subclass has its own table.
   • The base class table contains shared attributes, while subclass tables contain unique attributes.

3. Concrete Table Inheritance:

   • Each subclass has its own table with all required attributes.
   • There is no base class table, and all tables are considered separate entities.

The choice of which approach to use depends on your specific requirements and constraints. Carefully consider the pros and cons of each technique before making a decision.

For further insights, you can refer to the book section on inheritance mappers, which provides a deeper understanding of the mapping principles.

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