How to implement a super class, sub class relationship in the database?

Question

If I have a class called animal, dog and fish is the subclass. The animal have attribute called \"color\". Dog have the attribute called \"tail length\", and the fish don\

Answer 1

You could try it like this:

Animal
    PK animal_id
    FK animal_type
    STRING animal_name (eg. 'Lassie')

AnimalTypes
    PK animal_type
    STRING animal_type_name (eg. 'Dog')

AnimalAttributes
    PK attribute_id
    STRING attribute_name (eg. 'tail length')

AnimalToAttributes
    PK id
    FK animal_id
    FK attribute_id
    INTEGER value (eg. 20)

This way you can have one or many attributes per animal (it's up to you to choose).