There are four different strategies for representing an inheritance hierarchy:
 Use one table per concrete class and default runtime polymorphic behavior.
 Use one table per concrete class but discard polymorphism and inheritance relationships completely from the SQL schema. Use SQL UNION queries for runtime polymorphic behavior.

 Use one table per class hierarchy: enable polymorphism by denormalizing the SQL schema and relying on row-based discrimination to determine super/subtypes.
 Use one table per subclass: represent is a (inheritance) relationships as has a (foreign key) relationships, and use SQL JOIN operations.