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Entity Relationship Diagram: Applications of Information Technology & Information Systems

This document discusses key concepts in entity relationship diagrams including: Entities can represent real-world objects and concepts. Entity sets are collections of similar entities. Relationships define associations between entities. Relationship sets group similar relationships. Entities have attributes that describe their properties. Cardinality defines the numerical relationships between entities like one-to-one, one-to-many, many-to-one, and many-to-many. Effective ER diagrams are properly labeled, support the intended purpose, and highlight important aspects with a consistent approach.

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Dileep G
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58 views7 pages

Entity Relationship Diagram: Applications of Information Technology & Information Systems

This document discusses key concepts in entity relationship diagrams including: Entities can represent real-world objects and concepts. Entity sets are collections of similar entities. Relationships define associations between entities. Relationship sets group similar relationships. Entities have attributes that describe their properties. Cardinality defines the numerical relationships between entities like one-to-one, one-to-many, many-to-one, and many-to-many. Effective ER diagrams are properly labeled, support the intended purpose, and highlight important aspects with a consistent approach.

Uploaded by

Dileep G
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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APPLICATIONS OF INFORMATION

TECHNOLOGY & INFORMATION SYSTEMS

ENTITY RELATIONSHIP
DIAGRAM
GROUP MEMBERS
RP20030 – ASHISH CHIGULLAPALLI
RP20031 – MOHIT KUMAR
RP20033 – SHIVAM SHARMA
RP20036 – DILEEP KUMAR G
ENTITY
• An entity can be a real-world object, either animate or inanimate, that can be easily identifiable.
Examples of entities:
❖ Person: Employee, Student, Patient
❖ Place: Store, Building
❖ Object: Machine, product, and Car
❖ Event: Sale, Registration, Renewal
❖ Concept: Account, Course
Entity set
An gntity set is a collection of similar types of . entities. An entity set may contain entities with attribute
sharing similar values.
RELATIONSHIP
The association among entities is called relationship.
• Ex: Employee works_at department .
• Ex: Student enrolls in a course

❑ Relationship Set
A set of relationships of similar type is called a
relationship set. Like entities, a relationship too can
have attributes. These attributes are called
descriptive attributes.
ATTRIBUTES
Entities are represented by means of their properties, called attributes. All attributes have values.
Example : Student :- Name, Class, Age
Types of Attributes
• Simple attribute Simple attributes are atomic values, which cannot
be divided further. For example, a student's phone number is an atomic
value of 10 digits.
• Composite attribute - example, a student's complete name may have
first_name and last_name.
CARDINALITY
Defines the numerical attributes of the relationship between two entities or entity sets.
Different types of cardinal relationships are:

• One-to-One Relationships
• One-to-Many Relationships
• May to One Relationships
• Many-to-Many Relationships
Best Practices for Developing Effective ER
Diagrams

•Eliminate
•properly labeled
•There may be various valid approaches to an ER diagram. Supports
•Single time in the ER diagram
•Name
•Never
•highlight important portions

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