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What is a subtype in data Modelling?
A subtype is a sub-grouping of the entities in an entity type that is meaningful to the organization and that shares common attributes or relationships distinct from other subgroups. Create separate tables for the super type and all sub type entities for the following reasons: Data integrity enforced at database level.
Can subtypes have relationships?
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. When designing a data model for PEOPLE, you can have a supertype entity of PEOPLE and its subtype entities can be vendor, customer, and employee.
Are subtypes mutually exclusive?
Each subtype entity is an ACCOUNT and inherits the properties of ACCOUNT. The three different subtype entities of ACCOUNT are mutually exclusive. In order to distinguish one type of ACCOUNT from another, you can add the attribute “account-type” as the subtype discriminator.
What are domains in data modeling?
A domain is an independent model object that you can use to quickly assign properties to an attribute or column. You can define both logical and physical domains in the Domain Editor.
What is generalization in DBMS?
Generalization is like a bottom-up approach in which two or more entities of lower level combine to form a higher level entity if they have some attributes in common. In generalization, an entity of a higher level can also combine with the entities of the lower level to form a further higher level entity.
What is subject area in data modeling?
Subject Areas are group classifications of business data entities at their highest level of data object abstraction. They are defined during Enterprise Data Planning and are not usually affected by project- level changes in business data.
When to use supertype and subtype in data modeling?
SuperType and SubType in Data Modeling: At times, few entities in a data model may share some common properties (attributes) within themselves apart from having one or more distinct attributes. Based on the attributes, these entities are categorized as Supertype and Subtype entities.
How is a subtype related to a type?
The Car supertype has the common attributes of its subtypes while each of the subtypes has its different attributes. While Type is a definition of something, Category is a way to categorize something. While Service can be of only one type, it can be of more than one category—its relationship to Category entity is many-to-many.
How are type, subtype and category patterns related?
You can model the different types as subtypes. The following figure shows two subtypes of the Car Type entity: Passenger Car Type and Truck Type. The Car supertype has the common attributes of its subtypes while each of the subtypes has its different attributes. While Type is a definition of something, Category is a way to categorize something.
What is the relationship between type and category?
While Type is a definition of something, Category is a way to categorize something. While Service can be of only one type, it can be of more than one category—its relationship to Category entity is many-to-many.