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What is the ER Model?

by Bhumika

The Entity-Relationship model (ER model) is a type of entity-relationship model. It’s a data model at a high level. The data items and relationships for a given system are define using this model.

It creates a database’s conceptual design. It also creates a very simple and easy-to-design data view. Further, The database structure is depict as a diagram called an entity-relationship diagram in ER modelling.

Components of ER model

  1. Entity 

An entity is an object, location, person, or event that stores data in a database. Additionally, A rectangle represents an entity in an object-relationship diagram.

Entity type: An entity type is a list or a collection of things that share specific characteristics. In addition, Each type of entity in a database is define a name and a set of attributes.

Entity set: It’s a group (or collection) of similar entities with shared qualities or properties.

2. Attribute 

An attribute in an Entity-Relationship Model defines the traits or characteristics of an entity. An oval or ellipse shape is use in the ER diagram to symbolize it. Additionally, Each oval form represents a different attribute and is linked to the person in the rectangle shape.

Simple attribute: A simple attribute is calling an attribute which contains an atomic value and can not be divided further.

Key attribute: An attribute that can uniquely identify an entity in an entity set is known as a key attribute. Moreover, In the ER diagram, it represents a primary key. On the other hand, The key attribute is represent by an ellipse with an underlying line in an Entity Relationship diagram.

Composite attribute: A composite attribute is an attribute that is made up of two or more basic attributes. Moreover, An ellipse in an Entity-Relationship diagram defines it, and that ellipse is made up of additional ellipses.

Derived attribute: An attribute which can derive from other attributes is refers to as a derived attribute. Meanwhile, A dashed oval shape is use to represent these attributes in an entity-relationship diagram.

Multivalued attributes: An attribute that has several values for a particular entity.

3. Relationship 

Therefore, In the Entity-Relation Model, a relationship is use to define the relationship between two or more entities. In the ER diagram, it is illustrate by a diamond shape. 

Degree of Relationship

Degree of relationship can be categorize into the following types:

  • Unary Relationship
  • Binary Relationship
  • Ternary Relationship
  • N-nary Relationship

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