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.
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
Fruits →Apple. Orange, Mango Auto
Specialization is a process of identifying more specifies entity types
For Example Student and Teacher are more specific entity type than HUMAN