ER Model
ER Model stands for Entity-Relationship Model. A diagram is used in an entity-relationship model to show the database's structure. Because ER modeling requires you to assess all data requirements before creating your database, it is an organized method to database design.
The relationship between the entities that will be recorded in a database is represented graphically by an entity relationship diagram (ER Diagram). The ER Diagram is essentially a database's structural design. It serves as a framework made using specific symbols to specify how the database entities relate to one another. The three main components of an ER diagram are entities, attributes and relationships.
History of ER Model
ER Diagrams were suggested by Peter Chen in 1971 as a standard method for conceptual modeling. Although a lot of models were discussed and shown, none of them were appropriate. His model also took inspiration from Charles Bachman's data structure diagrams.
Use of ER Diagram in DBMS
1. With the help of an ER Diagram, you may better visualize the database and determine which fields must be included for a certain object.
2. A database's contents can be better understood with the help of an ER diagram.
3. It makes databases simpler and enables database designers to create databases more rapidly.
4. It is beneficial to use entity-relationship models to describe items.
5. It enables users to have a preview at the database's logical structure.
Symbols used in ER Diagram
Rectangles: Entity types are represented by this Entity Relationship Diagram symbol.
Ellipses: This symbol stands for attributes.
Diamonds: Relationship types are represented by this symbol.
Lines: It connects entity types with other relationship types and attributes to entity types.
A primary key: Here, it highlights the qualities
Double Ellipses: Represents properties with multiple values.
Components of ER Diagram
You base an ER diagram on three basic components:
1. Entity
- Weak Entity
2. Attributes
- Key Attributes
- Composite Attributes
- Multivalued Attributes
- Derived Attributes
3. Relationships
- One-to-One Relationships
- One-to-Many Relationships
- Many-to-One Relationships
- Many-to-Many Relationships
