Inheritance

Figure 1118. Introducing inheritance mapping

Mapping inheritance hierarchies to relational databases means bridging the gap between object oriented and relational models. We start with a slightly modified example from [Bauer2015]:

Figure 1119. Modelling payment.

(Animated PDF Version)

Modelling payment.

Simplified Billing details example derived from [Bauer2015]. Notice inherit.v1.BillingDetails being an abstract parent class of two concrete classes inherit.v1.CreditCard and inherit.v1.BankAccount. The attribute number applies both to bank account and credit card payments.


Since the relational model lacks inheritance completely we have to implement a database schema ourselves. We subsequently explore three main approaches each of which having its own advantages and disadvantages.