Defining Inheritance Mapping

Inheritance can be mapped using a table per class, joined subclass, or table per class hierarchy inheritance mapping strategy. You can apply any of these inheritance mapping strategies or mix them. You should define primary identifier on the entity class that is the root of the entity hierarchy.

• Table Per Class Hierarchy Inheritance Mapping Strategy
  The whole class hierarchy is mapped to one table. One character based type or integer type discriminator column is defined to distinguish instances of difference classes in the hierarchy.
• Joined Subclass Inheritance Mapping Strategy
  Each entity class is mapped to its own primary table. Each primary table has a reference key referring to a primary table of its parent class except for the primary table of the root class. The reference key should join on the primary key of the primary table.
• Table Per Class Inheritance Mapping Strategy
  Each class is mapped to its own primary table. All persistent attributes of the class, including inherited persistent attributes, are mapped to columns of the table.