CS 425 Database Organization ER Diagrams
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CS 425 Database Organization
ER DiagramsManju Muralidharan Priya
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Fundamentals
Notations
Building Blocks
Advanced concepts
EXIT
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CS561 Spring 2012 3
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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CS561 Spring 2012 11
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
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THANK YOU