Punjab College Of Technical Education College Website Presentation On:-
Punjab College Of Technical Education
College WebsitePresentation On:-
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.
OBJECTIVES• Store Information in Systematic Manner
• Reduce the Problem of End-user
• Easy to Store an Retrieval
• Track the Information
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
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.
Dependencies
What is Dependencies?
Types of Dependencies
Partial key Dependencies.
Primary key Dependencies.
Transitive key Dependencies.
Functional key Dependencies.
Generalization
Student
Grad Student Post Grad Student
Specialization
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
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
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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15
Employee Table
16
Student Table
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Completed ERD
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
• 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
DFD Zero LevelStudent Teacher
WebSite
Course Database Department
Level 1Student Teacher
Student result assignment Teacher T.T Teacher table
Student Table Teacher Table
WEBSITE DATABASE
Course Table Department Table Course Department Table
ER Of Student
Department + Course
Class With Professors(Plus Project Or Assignment)
ER Relationship
Contd…
BY HASH Generation
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