supertype entity definition
Supertype is an entity type that has got relationship (parent to child relationship) with one or more subtypes and it contains attributes that are common to its subtypes. Subtypes are subgroups of the supertype entity and have unique attributes, but they will be different from each subtype. Supertypes and Subtypes are parent and child entities respectively and the primary keys of supertype and subtype are always identical. E.g.