15.00 - Types of Entities - Teradata Database

Teradata Database Design

prodname
Teradata Database
vrm_release
15.00
category
User Guide
featnum
B035-1094-015K

Types of Entities

There are several different schemes for categorizing entities based on qualitatively different criteria. For purposes of this manual, the following two schemes are defined:

  • Major and minor entities
  • Supertype and subtype entities
  • The following table provides definitions for these types:

     

    Entity Type

    Definition

    Example

    Major

    An entity with relatively large cardinality and degree that is updated frequently.

    Order table

    Minor

    An entity with small cardinality and degree that is rarely updated.

    Minor entities are typically used in a single, 1:M association, and their primary key is often nonnumeric.

    Nation Code table

    Supertype

    A generic entity that is a superclass of one or more subtype entities.

    Supertype and subtype entities model the same real world entity at a high level.

    Supertypes must, by definition, have one or more reciprocal subtypes.

    Publications table

    Subtype

    A specific entity that is a disjoint subclass of one and only one supertype entity.

    Subtype and supertype entities model the same real world entity at a high level.

    Subtype entities typically have a higher degree than their supertypes, with the additional attributes describing detailed characteristics of the subtype that distinguish it from the other subtype entities of a mutual supertype.

  • Book table
  • Magazine table
  • Professional journal table
  • Conference proceedings
  • (all as subtypes of the supertype Publications)