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Generalization Specialization and Aggregation in DBMS

What is the need for Generalization Specialization Aggregation in DBMS ?


In this article, we will learn about Generalization Specialization and Aggregation in DBMS.

With large databases it was realised that the ER model was become a little more complex and inconvenient to use.

Thus by programmers there were some additions in the ER model were suggested to reduce down on the complexity of the program, some new concepts were added which were –

  1. Generalisation
  2. Specialisation
  3. Aggregation

We will learn more about them below –

Generalization Specialization Aggregation in DBMS

What is Generalization

In generalization we combine lower level entities to form a higher level entity. Thus its clear that it follows a bottom up approach.

Example –

In a bank there are two different types of accounts – Current and Savings, combine to form a super entity Account.

It thus follows system like classes, like super-classes and sub-classes right ?

It may also be possible that the higher level entity may also combine with further entity to form a one more higher level entity.

Generalization in DBMS

What is Specialization

While generalization may follow a bottom up approach. Specialization is opposite to that, it follows a top down approach rather.

Example –

Employee may be decomposed to further as current employee entity and ex employee entity.

Specialization in DBMS

What is Aggregation

Aggregation is simply when we would consider two different entities as a single entity together.

Example –

University offering course can be considered a same entity, when viewed from a student entity perspective.

Aggregation in DBMS
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