Department of Information Technology

Semester III- K Scheme

Unit 1 : Introduction to Database

System
(12 Marks)

Presented By :
Mrs. Samidha Chavan
Lecturer -Department of Information Tech.
Vidyalankar Polytechnic, Wadala (Mumbai)
1.1 Database Concepts
Data

Data is known facts that can

be recorded and stored on
computer media.
Data and Information

 Data is known facts that

can be recorded and stored
on computer media.

 Information is meaningful
data.
Data and Information

 Data is known facts that

can be recorded and stored
on computer media.

 Information is meaningful
data.
Data

Data is the raw material that can be processed

for any computing machine.

For example − Employee name, Product name,

Name of the student, Marks of the student,
Mobile number, Image etc.

Information

Information is the data that has been converted

into more useful or intelligent form.

For example: Report card sheet.

Database
Database is collection of data ,which is
organized in such away that it can be
easily accessed, managed or updated .
DBMS
( Database Management System )

It is software that used to manage -

storage ,access and security of data .
Database 1

Database 2
Examples of DBMS
• Microsoft Access
• Oracle
• MySQL
• IBM DB2
• SQL Server
• SQLite
Purpose of Database

Data generated As years passed by

which was recorded lots and lots of data
on paper began to generate
which became difficult
to manage.
Purpose of Database

As computers came in To manage this huge

picture tones of digital amount of digital data
data began to database came to
generate. existence.
Purpose of Database

“The main purpose of database is to store the

data electronically.
So that , this stored data can be processed,
and useful information can be derived from
it.”
Applications of database
 Banking
 Airlines and railways
 Sales
 Telecommunications
 Universities.
 Manufacturing
 E-commerce
 Credit card transactions.
 File Systems
v/s
Database approach
File System Disadvantages :
1. Data Redundancy :
( Some information is duplicated )

For Example – Account dept and Exam dept maintain record of

student, where Rollno, Name ,Address, Phone will get duplicated .

Rollno Rollno
Name Name
Address Address
Phone Phone
Email Exam
Fees result

Account department Exam department

File System Disadvantages :
2. Data Inconsistency:
( Different copies of same data are not matching )

Data inconsistency happens if update operation is not performed well

on all the files.

1001 1001
Rahul Rahul
Dadar
Kurla Dadar
98788990 98788990
R@gmail.com 90 % result
68,000

Account department Exam department

File System Disadvantages :
3. Data Isolation:

Data is scattered in different files , and files may have

different formats . So writing a new application program to
retrieve data is difficult . which result into data isolation

Isolated

Account department Exam department Library department

Application
Program
File System Disadvantages :
4. Concurrent Access Anomalies ( Problems):

If multiple users are updating data at the same time .

then ,it will result in inconstant data.

Class Teacher
Student File
Exam Section

Account Section
Advantages of DBMS :
1. Independence of Data and Programs :
In DBMS , database can be alerted independently.

2. Controlling Redundancy :
In DBMS , there is no redundancy , If Duplicate
Data is found then DBA can arrange that data in
non duplicate way .

3. Data sharing :
In DBMS , data can be easily share among multiple
users .

4. Data security :
DBA provides access to authorize users only .
File System v/s DBMS

File System DBMS

PC based small system Mainframe based Large
system
Cost : Less Cost : Expensive
Single User System Multiuser System
Data is isolated Data is integrated
Transaction concept not Transaction Concept
used used

Example :Foxpro Example :

Microsoft Access,
Oracle ,MySQL
Characteristics of database

• Sharing of data .
• Multiple users can access data.
• Security.
• Controlled Redundancy.
Let's Revise !
1. List 4 Names of DBMS software’s ?
• Microsoft Access
• Oracle
• MySQL
• IBM DB2
2. What is Data Redundancy ?
• Duplication of data is called Data redundancy

3. What is Data inconsistency ?

• Different copies of same data are not
matching
DBMS vs File System

File System DBMS

PC based small system Mainframe based Large
system
Cost : Less Cost : Expensive
Single User System Multiuser System
Data is isolated Data is Integrated
Transaction concept not Transaction Concept used
used

Example : FOXPRO Example :

Microsoft Access,
Oracle ,MySQL
Data Abstraction
Final
Product

Table : Student

Hiding complex details of data storage and data organization

from user is called “Data Abstraction”.

For Example : Email in Inbox

Levels of Data Abstraction
There are 3 levels of Data Abstraction
o View Level ( Part of data)
o Logical Level ( What data ?)
o Physical Level ( How data ?)
Levels of Data Abstraction

View Level  Show part of the data to

View 1 View 2 … View n user
 Complexity is hidden
 External view level

 What data is stored ?

Logical Level  Relationship among data
 Conceptual level

 How data is stored ?

Physical Level  Complex data structure
 Internal level
Example
View 1 :Office View 2:Teacher View 3 :Principal
Staff

View Level

Table : Student
Logical Level

Hard Disk Drive

Physical Level
Advantages : Data Abstraction

 It improves the security of the data.

 Multiple users can access their desired

data.
Think and Answer …
Identify the level of Data abstraction ?

How data is stored ? - Physical Level

What data is stored ? - Logical Level

Show part of the data to user - View Level

Data Independence
Data independence

 It is ability to modify schema definition at

one level without affecting a schema
definition on next level is called “Data
Independence”

 There are two types of data independence

• Physical data independence
• Logical data independence.
 Physical Data Independence
 It is ability to change internal level without
changing conceptual level or external level .
 It is ability to change physical schema without causing
application programs to be rewritten

View Level /
External

Logical Level/
Conceptual

Physical Level/ MODIFY

Internal
 Logical Data Independence
 It is ability to change conceptual level without
changing external level.
 It is ability to change logical schema without causing
application programs to be rewritten

View Level /
External

Logical Level/ MODIFY

Conceptual

Physical Level/
Internal
1.2 Database Architecture
 3 Tier
Architecture of DBMS
 3 Tier Architecture of DBMS

User (Presentation) Tier −

Client
GUI, Web Interface

Application (Middle) Tier -

Application Programs,
Application Server/ Web Server
Web Pages

Database (Data) Tier − Database

Database Server Management Systems
(DBMS)
 In 3 tire architecture communication take place from
client to application server and Application server to
Database.
 Application server is called “Middle Layer”
 Middle Layer process application code.
 Database server process Database queries.
 3 tire Architecture is used in W.W.W(World Wide Web)
 All client request for data, server gives that data to
client .
3 Tier Architecture of DBMS
User (Presentation) Tier −
 End-users operate on this tier and they know
nothing about database.
 At this layer, multiple views of the database can
be provided by the application.
 All views are generated by applications that reside
in the application tier.
3 Tier Architecture of DBMS
Application (Middle) Tier -
 Accepts requests from the clients
 Processes the requests and sends database
commands to the database server
 Act as intermediate layer between client and the
database server
3 Tier Architecture of DBMS
Database (Data) Tier −
 At this tier, the database resides along with its
query processing languages.
 We also have the relations that define the data
and their constraints at this level.
2 Tier Architecture of DBMS
 2 Tier Architecture of DBMS
 The 2-tier Architecture is based on a client-server
mechanism.
 In this type of architecture, the applications on
client-side interact directly with the database
present at the server-side.
 This interaction between client and server uses
Application Program Interface like ODBC and JDBC.
 ODBC − Open Database Connectivity
 JDBC − Java Database Connectivity
 When there are a large number of users at client
side to access the database, this architecture gives
a poor performance.
 The server side is responsible for delivering the
functionalities like query processing and
management of transactions.
 For example − Oracle, Sybase, Microsoft SQL Server
etc.
2 Tier Architecture of DBMS
 2 Tier Architecture of DBMS

Library system (OLD library system of a college )

Librarian at library counter, directly accesses the database on the server
to enter queries about a book. The database then updates to indicate that
the book is available or no longer available.
1.3 Database Models
Data Model ( 2 Marks )
 Data Model is collection of concept
which describe structure of database.

 Data Model is collection of data,

database schema, consistency
constraints .
Types of Data Model

Object based Record based

Logical Model Logical Model

Examples - Examples -
• ER Model • Network Model
• Object Oriented Model • Hierarchical Model
• Functional Data Model • Relational Data Model
Network Model

1. It is Record Based Logical Model .

2. It can represent Object and
Relationship.
3. It is based on Tree like structure with
many roots .
4. Many to many OR One to many
relationship is maintained .
Network Model

5. Network Model is more popular .

6. In this model, data is represented as
collection of records.
7. Records have fix formats .
8. It uses Client Server architecture
Network Model
“ Object and Relationship ”

Object Object

Relationships
 Network Model
One to Many Relationship
01 Sita Mumbai CO C1 Hardware

02 Gita Pune IF C2 Networking

03 Nita Nashik EJ C3 Animation

Many to Many Relationship

Fix Length Records
“ Tree like structure with many roots .”
Network Model

1. It is Record Based Logical Model .

2. It can represent Object and
Relationship.
3. It is based on Tree like structure with
many roots .
4. Many to many OR One to many
relationship is maintained .
Network Model

5. Network Model is more popular .

6. In this model, data is represented as
collection of records.
7. Records have fix formats .
8. It use Client Server architecture
Key Points to Remember :
Network Model

1.Record Based Logical Model

2.Object and Relationship.
3.Tree like structure
4.Many to many OR One to many
5.more popular
6.records.
7.fix formats
8.Client Server architecture
Q. Enlist different types of data
model.( 2 marks)
Answer : Different types of Data model are the
following:
 Hierarchical database model.
 Relational model.
 Network model.
 Entity-Relationship model.
Hierarchical Model

1. It is based on Tree like structure with

one root.
2. Data is stored in the form of parent child
relationship.
3. It contains root which is called parent.
4. It represent one to many relationship
5. It is not much popular than network
model .
6. It is used in Mainframe database system.
Example 1:Hierarchical Model
Employee Table
Ename Eid Salary
Mr. Ganesh 111 50000

1:N
Child Name Date of Birth
Sita 27/6/2000
Nita 8/12/2005

Child Table
Figure : ( One to Many )Parent Child Relationship
Hierarchical Model
Difference between
Network and Hierarchical model

Network Model Hierarchical Model

Network Model is more popular Hierarchical Model is not more
than Hierarchical and Relational popular
Model

One to Many , Many to many One to many relationship is

relationship is Maintained maintained

It is based on Tree like structure It is based on Tree like structure

with many Roots with one Root
Difference between
Network and Hierarchical model

Network Model Hierarchical Model

Example Example
Key Points : Hierarchical
Model
1. Tree like structure with one root .
2. parent child relationship.
3. root is called parent.
4. one to many relationship
5. not much popular
6. Mainframe database system.
Quick Revision
Q1. which database model is represented by
this diagram ?

Answer : Network Model

 Quick Revision

Q4. Hierarchical Model is based on Tree like

structure with _________.
[ many roots / one root]
Answer : One root

Q3. Hierarchical Model represent many to

many relationship . [ True / False ]
Answer : False
 Quick Revision
Network Model Hierarchical Model
Network Model is more Hierarchical Model is not
popular than Hierarchical more popular
and Relational Model

It is based on Tree like It is based on Tree like

structure with many structure with one Root
Roots
Relational Model

1. It was introduced by E.F.Codds .

2. It represent data in the form of table.
3. A table is a database object that store data
in the form of rows and columns.
4. Each row in the table represent collection of
related data values.
Example of Relational Model

Attributes
Table : Student
Rollno Name
1 Sita Tuple
2 Gita
3 Nita
Concepts of Relational Model
Table : Student
Rollno Name
1 Sita
2 Gita
3 Nita

1. Tuple - In Relational Model, row is called “Tuple”.

For example : Tuple 1 Sita

The above table have 3 Tuples.

 Concepts of Relational Model
Table : Student
Rollno Name
1 Sita
2 Gita
3 Nita

2. Attribute - Column Header is called Attribute .

For example : Student table has two attributes Rollno
and Name .

3. Degree of table – Number of attributes of table is

called “Degree of table”
For Example : Degree of Student Table = 2
 Concepts of Relational Model
Table : Student
Rollno Name
1 Sita
2 Gita
3 Nita

4. Domain - All permissible values are called Domain

For Example : Domain of Rollno are 1,2,3
Domain of Name are Sita , Gita, Nita .

5. Cardinality – Number of rows in a table is called Cardinality

For Example : Cardinality of Student Table = 3
Activity 1-
1. Number of rows in a table
2. All permissible values
3. Column Header
4. Row of the table
5. Number of attributes

Tuple 4 . Row of the table

Attribute 3 . Column Header

Degree of table 5 . Number of attributes

Domain 2 . All permissible values

Cardinality 1 . Number of rows in a table

Activity 2- Identify !
Emp_ID Emp_Name Emp_Address
1001 Mr. Rahul Mane Dadar
1002 Mr. Gaurav Tope Vashi
1003 Mr. Rajesh Patil Parel
1004 Mr. Ram Kumar Kurla

Tuple
Attribute Emp_ID,emp_Name,Emp_Address
Degree of table 3

Domain 1001,1002,1003,1004

Cardinality 4
Database Schema

Schema:
• The overall design of the database is known as schema.
• Database designers design database schemas to help
programmer to understand the database .
• A schema is defined as structure of database .
For Example : Table –Student
RollNo Name Percentage Branch

The Schema for above student table is :

Student ( RollNo, Name, Percentage, Branch)
Types of Database Schema

The database schemas are partitioned at different level

of abstractions.

Database Schemas are of three types :

1. Physical Schema
2. Logical Schema
3. Subschemas or View Schema
 Types of Schema
1.Physical Schema:
• The design of database at physical level is called Physical
Schema.
• It deals with How data is stored in storage media
• Data is stored in files and index is maintained
2. Logical Schema:
• The design of database at Logical level is called Logical
Schema.
• It deals with what data is stored and relationship between
data
• It defines tables and integrity constraints .
3. Subschemas or View Schema:
• The design of database at View level is called View
Schema or sub schema.
• Sub schema is subset of schema
• It describe end user interaction with database
Example of Database Schema

View Schema User 1 User 2 User 3

view view view

Student ( Roll_no ,Name ,Project_id)

Logical Schema
Roll_no Name Project_id

Physical Schema
Secondary Storage
File
Instance

• The collection of information stored in the databases at

a particular moment is called as an instance.
• Snapshot of data in the database at given instance of
time is called Instance.

For Example:
Student table may have following instance
RollNo Name Percentage Branch

1 Sita 60 IF

2 Gita 70 IF

3 Nita 80 IF
E.F Codd’s Rules
Rule 1 : Information Rule

All information in relational database is represented

by values in a table.
Values

Employee Table
empid ename salary phone

1 Sita 5000 89898989

2 Gita 6000 99999999
Rule 2 : Guaranteed Access Rule

Every data can be easily access by using combination

of table name , primary key value and column name .

Employee Table
empid ename salary phone

1 Sita 5000 89898989

2 Gita 6000 99999999

Employee + (empid=2)+ salary

Rule 3 : Systematic treatment of null values

RDBMS handles records that have unknown values (

Null values) .

RDBMS Distinguish between ZERO ( 0 ) and Null Values

.
empid ename salary phone

1 Sita 5000 89898989

2 Gita 6000 99999999
3 Nita 0

ZERO NULL
Rule 4 : Active online catalogue based on Relationa
Model

Description of the table and Contents of the table can

be queried by DML .
Rule 5 : Comprehensive data sub language Rule

RDBMS supports many languages but at least one of

them should allow user to do following things –
• Define table , view .
• Query and update data set .
• Set Constraints.
 Rule 6 : View updating Rule

Views are the virtual tables created by using queries to

show the partial view of the table.

That is views are subset of table, it is only partial table

with few rows and columns.

This rule states that views are also be able to get updated
as we do with its table.
Rule 7: High level insert, update, delete Rule

A database must support high-level insertion updating

and deletion on a table.

This rule states that every query language used by the

database should support INSERT, DELETE and UPDATE
on the all records.

For Example :
Suppose employees got 5% hike in a year. Then their
salary must be updated to reflect the new salary. A
single query should be strong enough to update the
entire employee’s salary at a time.
Rule 8 : Physical Data Independence

It is ability to modify physical schema without

rewriting application program .

For Example :
If the data stored in one disk is transferred to another
disk, then the user viewing the data should not feel
the difference or delay in access time.
Rule 9 : Logical Data Independence

It is ability to modify conceptual schema without

rewriting application program .

For Example :
If we split the EMPLOYEE table according to his
department into multiple employee tables, the user
viewing the employee table should not feel that these
records are coming from different tables.
Rule 10 :Integrity Independence

A database must be independent of the application that

use it .

Integrity constraints can be changed without changing

application program .
 Rule 11 :Distribution Independence

Application program are not affected by change in

distribution of Physical data.

For Example :
The end user should not be able to know about the
database servers. He should be able to get the records as
if he is pulling the records locally. Even if the database is
in different servers, the accessibility time should be
comparatively less.
 Rule 12 : No Subversion Rule

The language that access the information should not

bypass the integrity constraint.

For Example :
Update Student’s address query should always be
converted into low level language which updates the
address record in the student table only . It should not
be updating any other record other than that .
Overall Architecture of Database
 Query Processor: It interprets the requests received from
user.
Query Processor contains the following components –
 DML Compiler: It processes the DML statements into low
level instruction (machine language), so that they can be
executed.
 DDL Interpreter: It processes the DDL statements
 Embedded DML Pre-compiler: It processes DML statements
embedded in an application program into procedural calls.
 QueryOptimizer: It executes the instruction generated by
DML Compiler.
Storage Manager: Storage Manager is a program that
provides an interface between the data stored in the
database and the queries received.

Authorization Manager: It ensures role-based access control, i.e,.

checks whether the particular person is privileged to perform the
requested operation or not.

Integrity Manager: It checks the integrity constraints when the

database is modified.

Transaction Manager: It controls concurrent access by performing the

operations in a scheduled way that it receives the transaction.

File Manager: It manages the file space and the data structure used to
represent information in the database.

Buffer Manager: It is responsible for cache memory and the transfer of

data between the secondary storage and main memory.
Disk Storage: It contains the following components –

•Data Files: It stores the data.

•Data Dictionary: It contains the information about the structure of any

database object. It is the repository of information that governs the
metadata.

•Indices: It provides faster retrieval of data item.