Chapter No 2 :

Relational Data Model and Security and Integrity SpecificationMarks = 22

2.1----------------------------------- (10 Marks)• Data Model

• Network Model• Hierarchical Model• Relational Model

• Relational Model: - Basic Concepts Attributes and Domains. Key Concepts:- Candidate key, Primary key, Foreign key and Super key.

• E-R model, Components of ER Model, Types of attributes, role indicator, weak & strong entity set.

• Enhanced ER Model: Introduction, Specialization & Generalization.

2.2 ----------------------------------- (12 Marks)

• Relational Algebra and Relational Calculus.• Database Design: Relational database Design, Functional

dependencies, Normalization based on functional dependencies,

• Normal forms: 1NF, 2NF, 3NF, BCNF. Normalization based on multivalued dependencies, Normalization based on Join dependencies.

• Integrity Constraints: Domain Integrity Constraints, Entity integrity Constraints, Referential Integrity Constraints & on delete cascade.

• Database Security: introduction, Data security requirements.

DATA MODEL

It is a collection of tools used for describing data, relationships among data, data semantics and consistency constraints.

This is the way which describes the design of the database at physical, logical and view level.Different categories of Data models are

• Relational Model• Network Model• Hierarchical Model• ER Model

Hierarchical Data Modelo Developed in 1960.o It represent database as upside down tree.o Parent- Child relationship is present.o It support only one to many relationshipo Starting point is called as Root , subpart is called as node and the last node called as leaf

node.

Network Data Modelo Developed in 1964 and standardized in 1971.o It represent database as a arbitrary graph.o There is no parent-child relationship between nodes.o It supports many to many relationship.

Cust_id Cust_name Address Ac_no

Ac_no Balance ATM_NO

CUSTOMER

ACCOUNT

C101 Sameer

Pune A101 C102 Ajay Bangalore

A102

A101

200000

2000310012

A102

300000

2000310015

ATM_CARD ATM_NO

PIN CVV

2000310012

2278 134

2000310015

4587

475

.

Fig. Hierarchical Data Model

Root Node

Leaf Node

Cust_id Cust_name Address Ac_no

Ac_no Balance ATM_NO

CUSTOMER

ACCOUNT

C101 Sameer

Pune A101,A103

C102 Ajay Bangalore

A102,A103

A101

200000

2000310012

A102 300000

2000310015

Fig. Network Data Model

A103

300000

2000310015

ER Model o ER model is a Entity Relationship Model. o It is a graphical representation of database including relationships,

constraints, roles and cardinalities in database.o Components of ER model

oEntity SetoRelationship SetoAttribute

EntityAn entity is a “thing” or “object” in the real world that is

distinguishable from all other objects.

For example, each person in an enterprise is an entity. An entity has a set of properties, and the values for some set of properties may uniquely identify an entity.

AttributeAttributes are descriptive properties possessed by each member of an entity set. An entity is represented by a set of attributes.

For example Possible attributes of the customer entity set are customer_id, customer-name, customer_street and customer_city.

RelationshipA relationship is an association among several entities.

For example, we can define a relationship that associates customer Hayes with loan L-15. This relationship specifies that Hayes is a customer with loan number L-15.

Symbols For ER Diagrams

Rectangles, which represent entity sets.

Ellipses, which represent attributes.

Diamonds, which represent relationship sets.

Lines, which link attributes to entity sets

and entity sets to relationship sets.

Double ellipses, which represent multivalued attributes.

Dashed ellipses, which denote derived attributes.

Double rectangles, which represent weak entity sets

Types of Attributes :• Simple Attribute

• Primary Key Attribute

• Multivalued Attribute

• Derived Attribute

• Composite Attribute

Role of EntityThe function that an entity plays in a relationship is called that entity’s role.

We indicate roles in E-R diagrams by labeling the lines that connect diamonds to rectangles. Figure 2.12 shows the role indicators manager and worker between the employee entity set and the works-for relationship set.

Strong Entity Set• An entity set that has a primary key is termed a strong entity set.

Weak Entity Set• An entity set may not have sufficient attributes to form a primary key. Such an

entity set is termed a weak entity set. • For a weak entity set to be meaningful, it must be associated with another entity

set, called the identifying or owner entity set.

Types of Relationships / Mapping Cardinalities

PERSON PAN CARD

Query Language

• A query language is a language in which a user requests information from the

database.

• These languages are usually on a level higher than that of a standard database

programming language.

• Query languages can be categorized as either procedural or nonprocedural.

• In a procedural language, the user instructs the system to perform a

sequence of operations on the database to compute the desired result.

• For example Relational Algebra

• In a nonprocedural language, the user describes the desired information

without giving a specific procedure for obtaining that information.

• For Example Relational Calculus

Relational Algebrao The relational algebra is a procedural query language.o It consists of a set of operations that take one or two relations as input and produce a new

relation as their result. o The fundamental operations in the relational algebra are select, project, union, set difference,

Cartesian product, and rename.

Unary operations Binary operations

Unary Operationso Selecto Projecto Rename

Binary Operationso Uniono Intersectiono Set Differenceo Cartesian Product

Select Operation

o Select records from relation that satisfy the selection condition or search condition.

o Lower case Greek letter sigma (σ ) is used to denote selection.

o Selection criteria or selection condition appears as subscript to sigma.

o Consider schema BOOK (B_ID,TITLE,AUTHOR,YEAR,PRICE).

o Syntax

σ(Selection condition) (Relation)o Example

“Extract record of books having price less than 450/-”

σ(price < 450 ) (BOOK)

Project Operation

o Project operation display certain columns or attributes from table/relation.

o Lower case Greek letter pi (π ) is used to denote project operation.

o Column names appears as subscript to pi.

o Consider schema BOOK (B_ID,TITLE,AUTHOR,YEAR,PRICE).

o Syntax

π(Column Name1, Column Name2, ….., Column Name n) (Relation)o Example

“Extract title and author of books from BOOK relation”

π(title , author) (BOOK)

Rename Operation

• Rename operation use to rename relation/table name as well as attribute/column

names.

• Lower case Greek letter rho (ρ ) is used to denote rename operation.

1. Rename only relation/table name.

2. Rename only attribute/column names.

3. Rename both relation/table name and attribute/column names at a time.

1. Rename only relation/table name.

Syntax : ρs (R)

new name of relation old name of relation

Example : ρarkp_stud (student)

2. Rename only attribute/column names.

3. Rename both relation/table name and attribute/column names at a

time.

Rename attribute/column names

Syntax : ρ (new names for attributes) (R)

name of relation

Example : ρ (s_rn, s_name, s_class) (student)

Rename relation/table name as well as attribute names

Syntax : ρs (new names for attributes) (R)

new name of relation old name of relation

Example : ρarkp_stud(s_rn, s_name, s_class) (student)

Union Operationo Union operation is a binary operation.o It returns all data values that appear in either or both of the two relations.o Denoted by symbol ∪ .

Syntax :

Relation 1 Relation 2∪

Example :

BORROWER

Cust_name

Loan_no

Adams L_16

John L_12

Smith L_13

DEPOSITOR

Cust_name

Acount_no

Adams A_102

Johnson A_105

Sam A_209

BORROWER union

DEPOSITOR

Cust_name

Adams

John

Smith

Johnson

Sam

Π Cust_name (borrower ) ∪ Π Cust_name (depositor)

Intersection Operationo Intersection operation is also a binary operation.o It returns all data values which are common in two or more relations.

o Denoted by symbol ∩ .

Syntax : Relation 1 ∩ Relation 2

Example :

BORROWER

Cust_name

Loan_no

Adams L_16

John L_12

Smith L_13

DEPOSITOR

Cust_name

Acount_no

Adams A_102

Johnson A_105

Sam A_209

BORROWER intersection DEPOSITOR

Cust_name

Adams

Π Cust_name (borrower ) ∩ Π Cust_name (depositor)

Set Difference Operationo Set Difference operation is also a binary operation.o Set Difference operation allows us to find tuples which are present in first relation but not in

other relation.o Denoted by symbol “ “ .

Syntax : Relation 1 Relation 2

Example :

BORROWER

Cust_name

Loan_no

Adams L_16

John L_12

Smith L_13

DEPOSITOR

Cust_name

Acount_no

Adams A_102

Johnson A_105

Sam A_209

BORROWER set difference DEPOSITOR

Cust_name

John

Smith

Π Cust_name (borrower ) Π Cust_name (depositor)

Cartesian product Operationo Cartesian product operation is also a binary operation.o Cartesian product operation combines two or more relations in such a way that

each row of one relation combine with each row of other relation.

o Denoted by symbol “ × “ .

Syntax : Relation 1 × Relation 2

Example :borrower × depositor

BORROWER

Cust_name

Loan_no

Adams L_16

John L_12

Smith L_13

DEPOSITOR

Cust_name

Acount_no

Adams A_102

Johnson A_105

Sam A_209

BRROWER × DEPOSITOR

Cust_name Loan_no Cust_name Acount_no

Adams L_16 Adams A_102

Adams L_16 Johnson A_105

Adams L_16 Sam A_209

John L_12 Adams A_102

John L_12 Johnson A_105

John L_12 Sam A_209

Smith L_13 Adams A_102

Smith L_13 Johnson A_105

Smith L_13 Sam A_209

Fig. Cartesian Product

Relational Calculus

• It is a non procedural query language while relational algebra is procedural.• There are two variant of relational calculus

• Tuple Relational Calculus (TRC)• Domain Relational Calculus (DRC)

Tuple Relational Calculuso In TRC , All operations are depend on tuples.o A tuple variable is a variable that takes tuples of a particular relation. Tuple variable has same

number of columns as in relation.o A tuple relational calculus query has the form

{ T | p(T) }

where T is tuple variable

p(T) is formula that operates/describe tuple variable (T)o Example

query = “find all sailors with a rating above 7”

the tuple relational calculus query will be

{ S | S ϵ sailors ˄ S.rating > 7 ˄ S.AGE<30}

Domain Relational Calculuso In DRC , All operations are depend on attribute domains (columns).o A domain variable is a variable that contains values from some attribute domains. o A domain relational calculus query has the form

{ (X1,X2,….,Xn) | p(X1,X2,….,Xn)

where each Xi is either a domain variable or constant

p(X1,X2,….,Xn) is formula that operates/describe tuple variable (T)o Example

query = “find all sailors with a rating above 7 AND AGE IS BELOW 30”

the tuple relational calculus query will be

{ (I,N,T,A) | (I,N,T,A) ϵ sailors ˄ T > 7 ˄ A<30 }

SAILORS

sid sname rating age

22 Dustin 7 45

29 Brutus 1 29

31 Lubber 7 39

32 Andy 8 42

58 Rusty 10 35

Table : SAILORS

A B C D

a1 b1 c1 d1

a1 b1 c1 d2

a1 b2 c2 d1

a2 b1 c3 d1

If AB C then following condition must be present in relation R

T1.(AB) =(a1b1) &T2.(AB)=(a1b1)

Now consider T1(C) = C1T2(C) = C1

Therefore we can say that

AB C

Fig. A relation that satisfy FD AB C

FUNCTIONAL DEPENDENCY

NORMALIZATION Normalization can be defined as a process of

o Minimizing Redundancyo Minimizing Inconsistencyo Minimizing the insertion, deletion and update anomalies from the database.

There are different type of normal forms having there own condition OR criteria for normalization. Different normal forms are

First Normal form ( 1NF ) Second Normal form (2 NF ) Third Normal form (3 NF ) Boyce/Codd Normal form (BCNF )

First Normal form ( 1NF )

“ A relation is in 1 NF if and only if every attribute of a relation is single OR atomic”

DNAME DNUMBER DMGR_NO DLOCATIONS

Research 05 3320 {Delhi, Bombay,

Calcutta}Administration

04 2924 {Ahmedabad,

Nagpur}Headquarter 01 2221 {Chennai}

Fig. DEPARTMENT (not in 1NF )

DNAME DNUMBER DMGR_NO

Research 05 3320

Administration

04 2924

Headquarter 01 2221

DNUMBER

DLOCATIONS

05 Delhi

05 Bombay

05 Calcutta

04 Ahmedabad

04 Nagpur

01 Chennai

Fig. DEPARTMENT (In 1NF )

Fig. DLOCATIONS (In 1NF )

Second Normal Form ( 2NF )

“ A relation is in second normal if and only if it is in 1NF every nonprime attribute is

fully functional depend on primary key of a relation.”

Property_ID

City_Name

Sector_No Area Price Tax_Rate

Property_ID

City_Name

Sector_No Area Price

Table : PROPERTY

Table : PROPERTY_1

Table : PROPERTY_2

City_Name Tax_Rate

Third Normal Form ( 3NF )

“ A relation is in third normal form if and only if, it is in 2NF and there is no

transitive dependency in a relation.”

Property_ID

City_Name

Sector_No Price

Sector_No Area

Property_ID

City_Name

Sector_No Area Price

Table : PROPERTY_11

Table : PROPERTY_12

Table : PROPERTY_1

Boyc Codd Normal Form ( BCNF )

“ A relation is in BCNF if and only if, it is in 2NF and every determinant is a

candidate key.”

clientNo, interviewDate (Primary Key)

interviewDate, staffNo roomNo

ClientNo

interviewDate

interviewTime staffNo roomNo

CR76 13-May-02 10.30 SG5 G101

CR77 13-May-02 12.00 SG5 G101

CR74 13-May-02 12.00 SG37 G102

CR56 1-Jul-02 10.30 SG5 G102