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What is an entity supertype and subtype, and why is it used?
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Super types and Subtypes

  • An entity can be divided into serval subgroups or subtypes
  • An entity type that can be divided into subtypes is called super type.
  • A subtype is a subset ofasuper type that shares common attributes.
  • Subtypes behave in exactly the same way as any other entity type.
  • The primary keys of super type and subtypes are always identical

  • For example an entity CUSTOMER has the attribute Customer ID,Address and Phone.

  • A CUSTOMER can be an INIDIVUAL or ORGANIZATION.

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Generalization

  • Generalization is a process of identifying more general entity type.

  • For Example Human is a more general entity type than Student and Teacher > The entity type HUMAN contains attributes that are more general than other two entity type

  • It may contain the attribute like NAME, ADDRESS

  • The entity type STUDENT contains the attributes which are specifies to students like ROLLNO, MARKS CLASS

Examples

Fruits →Apple. Orange, Mango Auto

Specialization

  • Specialization is a process of identifying more specifies entity types

  • For Example Student and Teacher are more specific entity type than HUMAN

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