Introduction to DBMS

Ram Datta Bhatta

Data, Database, DBMS, Database
Application?
 Data and Database
Data: raw facts, such as numbers, words,
measurements, observations, or even just
descriptions of things. For examples: Ram
represents name of a person. Thus, it is also data.
Database: the collection of data. It generally
contains interrelated information. An employee
database may contain personnel information of
employees working in an organization, their duty,
job description, family information etc.
 DBMS
DBMS is a software package/program
designed to define, manipulate, retrieve, and
manage data in a database.
DBMS contains collection of interrelated data
and a set of programs to access those data.
A DBMS generally manipulates the data itself,
the data format, field names, record structure,
and file structure. Examples: MS-Access,
MySQL, MS-SQL, Oracle, Informix, IMS,
DB2, FoxPro etc.
 DBMS
• DBMS is:
– A collection of interrelated data.
– A set of programs to access the data.
– An environment that is both convenient and
efficient to use.
• DBMS stores data in such a way that it
becomes easier to retrieve, manipulate and
produce information.
 DBMS

Database System

Database DBMS
• Structured(University, Bank) SQL server
• Unstructured(Web Page) Oracle 8i,9,11
My SQL
DB2
 Database Application/System
 A computer program interacts with the database by issuing
an appropriate request (typically an SQL statement) to the
DBMS is known as database application.
 It is a software/program which uses database (generally as
backend) is known as database application.
 Let us consider an example of student management system
implementing in a school. Let us suppose the management
system has been developed using Java programming
language and database oracle. Here, Java has been used for
programming/processing purpose but actual information
(data about student) is contained in the database. Here, Java
is called front-end and oracle database is known as back-end.
 DBMS

End User

Database
Database Applications Management System

Database
 Use of DBMS (Applications)

 Banking : All transactions

 Airlines: Reservations, Schedules
 Universities: Registration, Grades
 Sales: Customers, Products, Purchases
 Manufacturing: Production, Inventory, Orders, Supply
chain
 Human Resources: Employee records, salary, tax
deductions.
 Online retailers: Order tracking.
 Why DBMS? How does it differ from
Traditional File System?
 Reduced Data redundancy and inconsistency.
 Easy in accessing data.
 Isolation of data and application
 Maintains Data Integrity
 Removes concurrent-access anomalies ( Concurrency
Control)
 Atomicity problems
 Multiple Views
 Enhanced Security
[For detail: see attached word document]
 Difference between file system and DBMS

File System DBMS

• File system is a software that • DBMS is a software for managing
manages and organizes the files in the database.
a storage medium(HDD) within a • In DBMS, there is no redundant
computer. data.
• Redundant data can be present in • It provides backup and recovery of
the file system data even if data is lost.
• It does not provide backup and • Efficient query processing is there in
recovery of data if it is lost. DBMS.
• there is no efficient query • There is more data consistency
processing in file system because of the process of
• There is less data consistency in normalization.
file processing system. • DBMS has more security
• File system provides less security mechanism as compared to file
in comparison to DBMS. system.
• It is less expensive as compared to • It has comparatively higher cost
DBMs. than file system.
 Levels of Abstraction,
Abstraction: Hiding background detail
To ease the user interaction with the database,
the developers hide internal irrelevant details
from users and provides abstract view of data
to users. This process of hiding irrelevant
details from user is called Data Abstraction
Three Levels of Data Abstraction or Three
Schema Architecture
Three levels of data abstraction
View Level (User)
External External External View Level
Schema Schema Schema (views describe
How users see the data)

Conceptual Logical Level

Schema (describes what data are to be stored in the
Database and describes what relation ship
Physical Schema exists among those data)
Physical(internal ) Level
(it is used to define that how the data
will be stored in block)
Databse
(Disk)
 Three level of data abstraction
1. Physical Level(Internal Level)
– This is the lowest level of data abstraction.
– It describes how data is actually stored in database. User can get the complex
data structure details at this level.
2. Logical Level(conceptual level)
– It describe what type of data?
– It describes how data is stored in database and what relationships exist among
those data. (pk, fk, relationships, constraints etc.)
3. View Level
 Highest level of data abstraction.
 This level describes only part of the database i.e. it describes the user interaction
with database system via application program that hide details of data types. At the
View Level, user just interact with system with the help of GUI and enters the
details at the screen, they are not aware of how the data is stored and what the data is
stored, such details are hidden from them.
 Schemas and instances

 Overall design of the database is called

schema. E.g. given a schema shows the
relationship between three tables : course,
student, section
 The diagram only shows the design of the
database, it does not show the data present in
those tables. Schema is only the structured
view( design) of a database.
Schema

Course Student

Course_ID Student_ID
Course_ name Student_name
Department Course_ID

Section
Student_ID
Section_ID
Course_ID
 Types of Schemas

• Physical Schema
– It describes database design at physical level i.e. physical
structure of database.
– How the data stored in blocks of storage is described at this
level.
– Database administrator works at this level.
• Logical Schema
– It describes database design at logical level i.e. logical
structure of database.
– Database programmer works at this level.
 Instances

 The data stored in the database at particular moment of

time is called instance of database.
 Example: lets say we have a single table Student in the
database. Today the table has 100 records, so today the
instance of the database has 100 records. Lets say we are
going to add another 100 records in this table by
tomorrow so the instance of the database tomorrow will
be 200 records in the table. In short, at a particular
moment the data stored in database is called the instance,
that changes over time when we add or delete data from
the database.
 Data independence
The ability to modify the schema at one level of the database
system without the altering the schema at next higher level.
Two types of data independence
1. Logical Data Independence
Ability to modify the logical schema without changing the
external view and application.
2. Physical Data Independence:
Ability to modify the physical schema without changing the
logical schema.
Data independence

User User User

View Level

Logical Data Independence

Conceptual Schema

Physical Data Independence

Physical Schema

database
 DBMS Architecture

• Database Architecture can be seen as a single tier or

multitier.

DDBMS Architecture

1-tier Architecture 2-tier Architecture 3-tier Architecture

 Single or 1-tier Architecture

• In a single or 1-tier architecture, the database is

directly available to the user. The client, server and
database all reside on the same machine i.e. the user
can directly sit on the DBMS and uses it.
• Any changes done here will directly be done on the
database itself. It does not provide a handy tool for
end users.
• No network connection is required to perform the
action on the database.
 1-tier architecture is used

 In a single or 1-tier architecture, the database is directly available

to the user. The client, server and database all reside on the same
machine i.e. the user can directly sit on the DBMS and uses it.
 Any changes done here will directly be done on the database
itself. It does not provide a handy tool for end users.
 No network connection is required to perform the action on the
database. Database user

database system

1-tier architecture
 2-tier architecture

Client 1 Client 2 Client 3

Network Connection

Data
Server

• It is same as the client server.

2-Tier Architecture
 2-tier architecture

 In the 2-tier architecture, applications on the client end can

directly communicate with the database at the server side.
 An Application Programming Interface(APIs) like ODBC(
Open Database Connectivity) and JDBC(Java Database
Connectivity) are used by client side programs to call the
DBMS.
 The user interface and application programs are run on the
client side.
 To communicate with the DBMS, client side application
established a connection with the server side.
 The server side responsible to provide the functionalities like
query processing and transaction management.
 3-tier architecture

Client 1 Client 2 Client 3 Client Layer

Client
Application
Application server Business Layer

Data Data Layer

source
3- Tier Architecture
 3-tier architecture

 3-tier architecture contains another layer of application server

between the client and database server.
 In this architecture, client can’t directly communicate with the
database server.
 The application on the client end interacts with an application
server which further communicates with the database server
and then query processing and transaction management takes
place.
 The intermediate layer of application server acts as a medium
for exchange of data between the database server and client.
Thank you