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Entity Modeling
Last week has been discussed Context diagram
and functional diagram
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Entity Modeling
Using Entity Modeling to create the
Effective and Efficient database
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Outline
Terminology
Type of relationship
Obligatory Relationship
E-R Model
Symbols in E-R Model
Example of E-R Model
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Terminology
Entity
Attribute
Table
Relationship
Occurrence
Determinant
Identifier
Code
Foreign Identifier
Relationship Entity
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Entity
Any objects and concepts
Have mean to the organization
Or relevance to the system being design
Needed to store in the database
Example : student; lectures; subjects;inventory, customer;
invoice
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Attribute
Any characteristics, elements to define or to
describe entity
Example : entity = Student
attributes: student number
name
birth date
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Custom
NumberName Address
Customer
InventoryInvento
ry No
Descri
ptionUnits Quantity
On HandUnit
Price
Table
Means to show an entity and its attributes
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Relationship
The association of two or more of entities
Needed to store in the database
Example : invoice FOR customer
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Occurrence
Every rows of table
Customer
Customer
Number
Customer
Name
Customer
Address
C0001 Ali Padang
C0002 Budi Bukittinggi
occurrence
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Determinant and Identifier
Determinant any attribute of the the entity that
determine the value of other attribute; such as
name determine the address of customerIdentifier is one or the
combination of the
attribute that identify of the occurrence of the
entity; so it should be unique; such as customernumber
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Foreign Key and Relationship Entity
Foreign Key is any attributes of the entity come
from other entity, means to represent the
relationship of those entitiesRelationship Entity is the new
entity used to
represent the relationship two or more entities
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Invoice
No.Date Custom Number Custom
NumberName Address
Invoice
No.Inventory
No
Quantity
Invoice Customer
Invoice details Inventory
Inventory No
Description
Units QuantityOn Hand Unit
Price
Foreign Key
Relationship
entity
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Types of Relationships
The three most important relationship type
One to One Relationship
One to Many Relationship
Many to Many Relationship
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One to One Relationship
If one occurrence has relationship with nor more
than one occurrence in other entity
Lecturers Subjects
Ali English
Susi Math
Dewi Accounting
Lecture Teaches Subject1 1
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One to Many Relationship
Ali English
Math
Dewi Accounting
Lecture Teaches Subject1 M
Ahmad Management
Lecturers Subjects
StatisticsAkmal
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Many to Many Relationship
Ali English
Susi Math
Dewi Accounting
Lecture Teaches SubjectM N
Ahmad Management
Lecturers Subjects
StatisticsAkmal
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Entity Relationship Model
Shows or represents all entities and
relationships relevance to the
database being designed
Documenting all data to store in
database
As the basis to design phyisics
database
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Symbols for E-R Model
= entity
= relationship
= connective line
1 , M , N = relationship type
= Obligatory relationshipO
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