CS 425 Database Organization

ER DiagramsManju Muralidharan Priya

Fundamentals

Notations

Building Blocks

Advanced concepts

EXIT

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ER Diagrams

• An abstract and conceptual representation of data.

• It is used to design database schema

• Commonly used during Requirement Analysis phase.

• Has entities , attributes and relationships

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ENTITIES

StudentSeminar

ClassroomDesk

PersonObjectPlaceEvent

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ATTRIBUTES

STUDENT NAME

S_ID

FNAME

AGELNAME

DOB

CLASS

Why use Key?

Simple attribute

Derived attributeComposite attribute

Multi-value attribute

Primary key

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RELATIONSHIPS

Member ofSTUDENT TEAM

since

Association between entities

Can have attributes

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STUDENT

TEAM_ID

S_ID

Member of TEAM

sinceTEAM_ID

Relationships contd.

Here TEAM_ID is the foreign key connecting the entities

Establishing Relationships

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CARDINALITYNumber of entities in a relationship

One to One relationshipOne to Many relationshipMany to One relationshipMany to Many relationship

Manager DepartmentManages1 1

Student Class1 N

BelongsStudent Quiz TeamBelongsN 1

StudentTeacherN N

Teaches

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ROLESRoles of entities in relationships

Member of

STUDENT TEAM

Leader ofLeader Lab Team

MemberQuiz Team

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NOTATIONS

Chen Notation

Member ofSTUDENT CLUB

1 N

Crow’s Foot Notation

Member of

Has

Min-Max / ISO

(0,1)Member of

(0,N)Has

<<Relationship>>

<<Entity>> <<Entity>>< Has

Member of >

0..N1

UML Notation

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WRAP UP…

STUDENT

NAME

S_ID

FNAME

AGE

LNAME

CLASS

DOB

Member of

TEAM

sinceTEAM_ID

Member of Has

1 N

ENTITIES RELATIONSHIPSATTRIBUTES CARDINALITY ROLES

THANK YOU