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Punjab College Of Technical Education
College WebsitePresentation On:-
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E-R Model E-R Model: Entities.
Attributes.
Relationship.
Steps to form E-R Model: Identify Entities.
Find Relationship.
Draw rough E-R.
Fill the cardinality.
Define Primary key.
Draw key based ERD.
Identity Attributes.
Map Attributes.
Draw full attribute of ERD.
Check Result.
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OBJECTIVES• Store Information in Systematic Manner
• Reduce the Problem of End-user
• Easy to Store an Retrieval
• Track the Information
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Users
• Different users can access data• Depending on their degree of expertise users
are classified in the following groups– Naïve Users (ATM user)
– Online Users– Application Programmers– Sophisticated Users– DBA
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Entity Relationship Model
• Entity – It is anything real or abstract about which we
want to store the data .
• Relationship – It specifies the association that
exists between one or more entities.
• Attribute – It is the characteristic which is common to
all or most instances of particular entity.
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Dependencies
What is Dependencies?
Types of Dependencies
Partial key Dependencies.
Primary key Dependencies.
Transitive key Dependencies.
Functional key Dependencies.
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Generalization
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Student
Grad Student Post Grad Student
Specialization
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Normalization
• It is a process during which redundant relation schemas are
decomposed by breaking up their attributes in to smaller
relation schemas that possess desirable properties.
1. First N/F
2. Second N/F
3. Third N/F
4. BNC N/F
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Eliminate Repeating Groups
Second N/FFirst N/F
Third N/FBC N/F
Removing Partial key dependency
Eliminate Transitive key dependency
Eliminate Functional dependency
Normalization Form
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Attributes
• Characteristics of entities
• Domain is set of possible values
• Primary keys underlined
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Relationships• Association between entities• Connected entities are called participants• Operate in both directions• Connectivity describes relationship classification– 1:1, 1:M, M:N
• Cardinality– Expresses number of entity occurrences associated
with one occurrence of related entity
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Comparison of E-R Modeling Symbols
Figure 3.36
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Employee Table
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Student Table
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Completed ERD
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Keys
• Candidate Key– A minimal set of attributes that uniquely identifies a tuple
• Primary Key– The candidate key chosen as the identifying key of the
relation
• Alternate Key– Candidate keys which are not primary keys
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• Foreign Key– An attribute (or set of attributes) in table R1 which
also occurs as the primary key of relation R2. – R2 is called the referenced relation. – Foreign keys are also called connection keys or
reference attributes.
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Database vs. File SystemsFigure 1.6
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DFD Zero LevelStudent Teacher
WebSite
Course Database Department
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Level 1Student Teacher
Student result assignment Teacher T.T Teacher table
Student Table Teacher Table
WEBSITE DATABASE
Course Table Department Table Course Department Table
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ER Of Student
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Department + Course
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Class With Professors(Plus Project Or Assignment)
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ER Relationship
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Contd…
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BY HASH Generation
THANK YOU!!!