How Do You Effectively Map Object-Oriented Inheritance to a Relational Database?

Mapping Object-Oriented Inheritance to a Relational Database Scheme

Canonical data models often exhibit inheritance relationships, where attributes are inherited from parent to child entities. Translating this inheritance to a relational database scheme can be a complex task.

Single Table Inheritance (STI)

This approach uses a single table to represent all classes in the inheritance hierarchy. Each row contains all the attributes of its associated class. While STI is straightforward to implement, it can result in a large number of null values for attributes that are not relevant to all classes.

Class Table Inheritance (CTI)

CTI creates separate tables for each class in the inheritance hierarchy. Each table contains the attributes specific to that class and links to the parent table. This approach reduces the number of null values but requires more complex queries to navigate the inheritance tree.

Concrete Table Inheritance (CTI)

CTI also creates separate tables for each class, but the tables share a common set of key fields. This allows for more efficient queries and better performance than STI or CTI.

The choice of which inheritance mapping strategy to use depends on the specific requirements of the database scheme. Martin Fowler's Patterns of Enterprise Application Architecture provides a comprehensive discussion of these approaches and offers guidance on selecting the most appropriate one.

The above is the detailed content of How Do You Effectively Map Object-Oriented Inheritance to a Relational Database?. For more information, please follow other related articles on the PHP Chinese website!