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Chapter 3. Relational Model. Chapter 3 in Textbook. Database Design. Steps in building a database for an application:. Real-world domain. Conceptual model. DBMS data model. Create Schema (DDL). Load data (DML). Relational Model. - PowerPoint PPT Presentation
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Chapter 3
Relational ModelRelational Model
Chapter 3 in Textbook
Lilac Safadi
Relational Model
2
Database DesignDatabase Design
Steps in building a database for an application:
Real-world domain
Conceptualmodel
DBMS data model
Create Schema
(DDL)
Load data(DML)
Lilac Safadi
Relational Model
3
Relational ModelRelational Model
In the relational model, all data is logically structured within relations (tables).
Lilac Safadi
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Relational Data StructureRelational Data Structure
4170010
4182000
4182034
4188134
4189860
4192134
StudentNo
Al-Saleh
Al-Ghanem
Al-Fahad
Saod
Rashed
Al-Fahad
LName
Amal
Nora
Laila
Amal
Rana
Rania
FName Initial
M.
A.
A.
F.
I.
M.
DOB
04-06-78
02-12-79
01-11-74
22-04-73
30-01-78
19-03-79
GPA
3.91
4.20
4.01
3.01
2.31
3.50
STUDENT
Attributes
Tuples
Cad
inal
ity
Rel
atio
n
Degree
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Relational Data StructureRelational Data Structure
• Relation is a table with columns & rows. Holds information about entities.
• Attribute is a named column of a relation.
• Domain is the set of allowable values for one or more attributes. Every attribute in a relation is defined on a domain.
• Tuple is a row of a relation.
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Relational Data StructureRelational Data Structure
• Degree of a relation is the number of attributes it contains.
• Cardinality of a relation is the number of tuples it contains.
• Relational database is a collection of normalized relations with distinct relation names.
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DomainsDomains
4170010
4182000
4182034
StudentNo
Al-Saleh
Al-Ghanem
Al-Fahad
LName
Amal
Nora
Laila
FName Initial
M.
A.
A.
DOB
04-06-78
02-12-79
01-11-74
GPA
3.91
4.20
4.01
STUDENT
StudentNo
LName
FName
Initial
Student Name
Last Name
First Name
Initial
DefinitionAttribute
DOB
GPA
Domain Name
Date of Birth
Great Point Average
Digits: size 7
Character: size 15
Character: size 15
Character: size 3
Date: range 01-01-20, format dd-mm-yy
Real: size 3, decimal 2, range 0-5
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Relational KeysRelational Keys
• Primary Key (PK) to identify tuples uniquely within the relation
• Foreign Key (FK) is an attribute, or set of attributes, within one relation that matches the CK of some relation. Used to represent relationship between tuples of two relations.
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Relational KeysRelational Keys
4170010
4182000
4182034
4188134
4189860
StudentNo
Al-Saleh
Al-Ghanem
Al-Fahad
Saod
Rashed
LName
Amal
Nora
Laila
Amal
Rana
FName Initial
M.
A.
A.
F.
I.
DOB
04-06-78
02-12-79
01-11-74
22-04-73
30-01-78
GPA
3.91
4.20
4.01
3.01
2.31
STUDENT
D001
D002
D003
DeptNo
Computer Science
Business Administration
Science
Department Name
Build # 20
Dept
D001
D001
D002
D003
D001
Location
Build # 45
Build # 6
DEPARTMENTPrimary Key
Foreign Key
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DB RelationsDB Relations• Relation schema is a named relation defined by a set of
attributes
If A1, A2, .., An are a set of attributes, then relation schema R is:
R = (A1, A2, .., An)
• Relational schema is a set of relation schemas, each with a distinct name
If R1, R2, .., Rn are a set of relation schemas, then relational schema R is:
R= {R1, R2, .., Rn}
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Relation SchemaRelation Schema
4170010
4182000
4182034
4188134
4189860
StudentNo
Al-Saleh
Al-Ghanem
Al-Fahad
Saod
Rashed
LName
Amal
Nora
Laila
Amal
Rana
FName Initial
M.
A.
A.
F.
I.
DOB
04-06-78
02-12-79
01-11-74
22-04-73
30-01-78
GPA
3.91
4.20
4.01
3.01
2.31
STUDENTDept
D001
D001
D002
D003
D001
STUDENT (StudentNo, Lname, Fname, Initial, DOB, GPA, Dept)
E/R Relational ModelE/R Relational Model
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Relational ModelRelational Model
• Represent each entity with a relation• attributes become the relation attributes
STUDENT (StudentNo, Lname, Fname, Initial, DOB, GPA, Dept)
DEPARTMENT (DeptNo, Department Name, Location)
Entity TypeEntity Type
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Relational ModelRelational Model
A weak entity type relation must include its key and its strong entity type PK as a FK. The combination of the two keys form the PK of the weak entity.
Weak Entity TypeWeak Entity Type
EMPLOYEE
EmpNo
LName FName
DOBDepNo FName
DEPENDENThas
EMPLOYEE (EmpNo, Lname, Fname, DOB)DEPENDENT (DepNo, EmpNo, FName)
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Relational ModelRelational Model
• Identify an entity type (S) (preferably total participator)• Include the PK of the other entity (T) as a FK in S • Add attributes that describes the relationship
1:1 Relationship1:1 Relationship
BRANCHmanageEMPLOYEE
EMPLOYEE(EmpNo, Lname, Fname, DOB)
BRANCH(BrnNo, Name, EmpNo, StartDate, EndDate)
1 1
(0,1) (1,1)
StartD EndDEmpNo
LName FName
DOBName
BrnNo
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Relational ModelRelational Model
• Identify a participating entity type (S) on the m-side• Include the PK of the other entity type (T) as a FK in S• Add attributes that describes the relationship
1:M Relationship1:M Relationship
BRANCHallocateEMPLOYEE
EMPLOYEE(EmpNo, Lname, Fname, DOB, BrnNo)
BRANCH(BrnNo, Name)
M 1
EmpNo
LName FName
DOBName
BrnNo
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Relational ModelRelational Model
• Create a relation R to represent the relationship• Include the PK of participating entity types (T & S) as FK in R. The combination of the two FK will form the PK of R• Add attributes that describes the relationship
M:N RelationshipM:N Relationship
PROJECTwork-onEMPLOYEE
EMPLOYEE(EmpNo, Lname, Fname, DOB)
PROJECT(ProjNo, Name)
Work-on(EmpNo,ProjNo, hours)
M N
hoursEmpNo
LName FName
DOBName
ProjNo
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Relational ModelRelational Model• Create a relation R to represent the relationship• Include the PK of the participating entities as FK in R. The combination of all FK form the PK of R.• Add attributes that describes the relationship
n-ary Relationshipn-ary Relationship
SUPPLIERcontractBUSINESS
BUSINESS(BizNo) LAWYER(LawNo) SUPPLIER(SupNo)
contract(BizNo, SupNo, LawNo, StartDate, EndDate)
Lawyer
StartD EndDBizNo
LawNo
SupNo
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Relational ModelRelational Model
Include its simple components in the relation
Composite AttributeComposite Attribute
EMPLOYEE
emp_no
name DOB
LNameinitial FName
EMPLOYEE(EmpNo, Fname, initial, Lname, DOB)
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Relational ModelRelational Model• Suppose A is a relation that contains the multivalued attribute
• Create a relation R to represent the attribute
• Include the PK of A as FK in R
•The PK of R is the combination of the PK of A (FK) & the multivalued attribute
MultiValue AttributeMultiValue Attribute
EMPLOYEE
EmpNo
DOB
Tel_no
EMPLOYEE(EmpNo, DOB)
TELEPHONE(EmpNo, tel_no)
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Relational ModelRelational ModelEEREERSpecializationSpecialization
SECRETARY TECHNICIAN ENGINEER
EMPLOYEE(EmpNo, Fname, Lname, DOB, Salary,TypingSpeed,TGrade, EngType, Secretary Flag, Technician Flag, Engineer Flag)
EMPLOYEE
EmpNo
Fname
LName
DOB
Salary
o
TypingSpeed EngType
TGrade
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Relational ModelRelational ModelEEREERSpecializationSpecialization
SECRETARY TECHNICIAN ENGINEER
SECRETARY(EmpNo, Fname, Lname, DOB, Salary,TypingSpeed)TECHNICIAN(EmpNo, Fname, Lname, DOB, Salary,Tgrade)ENGINEER(EmpNo, Fname, Lname, DOB, Salary, EngType)
EMPLOYEE
EmpNo
Fname
LName
DOB
Salary
d
TypingSpeed EngType
TGrade
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Relational ModelRelational ModelEEREEROptional/NonDisjointOptional/NonDisjoint
SECRETARY TECHNICIAN ENGINEER
EMPLOYEE(EmpNo, Fname, Lname, DOB, Salary)SUB-EMP(EmpNo, TypingSpeed,TGrade, EngType, Secretary Flag, Technician Flag, Engineer Flag)
EMPLOYEE
EmpNo
Fname
LName
DOB
Salary
o
TypingSpeed EngType
TGrade
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Relational Model
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Relational ModelRelational ModelEEREEROptional/DisjointOptional/Disjoint
SECRETARY TECHNICIAN ENGINEER
EMPLOYEE(EmpNo, Fname, Lname, DOB, Salary)SECRETARY(EmpNo, TypingSpeed)TECHNICIAN(EmpNo, Tgrade)ENGINEER(EmoNo, EngType)
EMPLOYEE
EmpNo
Fname
LName
DOB
Salary
d
TypingSpeed EngType
TGrade
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ViewsViews
Base relation is a named relation corresponding to an entity in the conceptual schema, whose tuples are physically stored in the DB
View is a derived relation. Virtual, may not exist, but dynamically derived from one or more base relations. The only information about a view that is stored in the database is its structure.
The external model can consist of both conceptual level relations (base relations) and derived views.
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ViewsViews
4170010
4182000
4182034
4188134
StudentNo
Al-Saleh
Al-Ghanem
Al-Fahad
Saod
LName
Amal
Nora
Laila
Amal
FName Initial
M.
A.
A.
F.
DOB
04-06-78
02-12-79
01-11-74
22-04-73
GPA
3.91
4.20
4.01
3.01
STUDENTDept
D001
D001
D002
D003
4170010
4182000
4182034
4188134
StudentNo GPA
3.91
4.20
4.01
3.01
STUDENT_GPA
View
BaseRelation
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Purpose of ViewsPurpose of Views
• Provides security mechanism by hiding parts of the DB from certain users
• Customize data to user’s needs, so that the same data can be seen by different users in different ways
• Simplify complex operations. It allow you to work with data from different tables simultaneously.
• Supports logical data independence
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Relational IntegrityRelational Integrity
Data integrity refers to the validity, consistency, and accuracy of the data in the database.
Integrity rules are constraints that apply to all instances of the DB.
Two integrity rules for the relational model:- Entity integrity- Referential integrity
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Relational IntegrityRelational Integrity
Entity Integrity: Ensures that there are no duplicate records within the table. In a base relation, no attribute of a PK can be null
Referential Integrity: If a FK exists in a relation, either the FK value must match a CK value of some tuple in its home relation or the FK value must be wholly null.
Enterprise constraints: rules specified by the users or DBA of the DB based on the ways an organization perceives and uses its data(e.g.number of staff working in a branch is at most 20)
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Summary of Relational ModelSummary of Relational Model
• Relational database• Relation, attribute, tuple, degree, cardinality• Primary Key, Foreign Key• Relation schema, Relational database schema• Relational Integrity, Entity Integrity,
Referential Integrity, Enterprise Constraints• Views