DBMS ER Model - MetaTutorials


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ER Model is also known as the Entity-Relationship model or Entity Relationship Diagram. 
ER Model (Entity-Relationship Model) is a model that defines or describes the structure of the database. This model was designed by Peter Chen in the 1976 paper.  
It is a high-level model representing the relationship between the data in the database. It is considered as the best option at the view level which will helps the database administrators in the future to design the database easily. DBMS provides the ER diagram as a tool for representing the ER model. 

Components of ER Model

Following are the three major components of the Entity-Relationship model:
  1. Entity
  2. Attribute
  3. Relationship
If you want to learn the components of the ER model in detail, then click here

Why Use ER Model in DBMS

Following are the various reasons for using the ER Model in Database Management System:
  • The main reason is that it provides the graphical or conceptual view of any database. 
  • This model is used by the database administrators as a blueprint, which helps them to design or implement databases in the future.  
  • It helps to describe how the database tables are connected. 
  • This model also describes the entities and attributes. 

What is an ER Diagram

ER Diagram (Entity-Relationship Diagram) is a diagram which identifies the entities and relationship between those entity sets in the database. 
It allows users to draw the database logical structure. ER diagram represents the entities, attributes of an entity, and the relationship in an ER model. This diagram is widely used in designing the database. 

ER Diagram Notations or Symbols

Following are the basic symbols or notations which are used in creating a simple Entity-Relationship diagram:
1. Rectangle: This symbol represents the entity types in an ER diagram. 
2. Ellipse: This symbol indicates the attributes of an entity. 
3. Diamond: This symbol represents the relationship set. 
4. Lines: Lines are used to link attributes(s) to entity set(s) and entity set(s) to relationship set(s). 

Following are the advanced symbols or notations which are also used in creating a high-level Entity-Relationship diagram:

Advantages of ER Model

Following are the benefits or advantages of the Entity-Relationship model in DBMS:
  • Any user can easily build and understand the ER model for the database.
  • DBMS user can easily draw ER diagrams for any database if he/she knows the relationship between entities and attributes. 
  • Entity-Relationship models can be easily converted into other data models such as hierarchical, relational, and network data model.  
  • It is a communication tool that is so effective for database designers. 

Disadvantages of ER Model

Following are the limitations or disadvantages of the Entity-Relationship model in DBMS:
  • The main disadvantage of the ER model is that it is especially popular for designing high-level designs. 
  • As compared to other data models, this model represents the limited constraints and relationships. 
  • In the ER model, some information might be hidden or lost.