lecture 2 database database system dbms

8/14/2019 Lecture 2 Database Database System DBMS

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DBMS

Lecture 2

Database

Database System

DBMS

Hitesh Mahapatra


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Introduction to Database

Collection of data related to a particular topic

Single large file that contains all the data

Series of Rows and Columns

Collection of Tables, Forms, Reports etc


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Database

A database is a computerized record

keeping system

Database itself can be regarded as a kind

of electronic filing cabinet

It is a repository for the collection of

computerized data files


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More completely, it is a system involving data,

the hardwarethat physically stores that data, the

software that utilizes the hardware's file system

in order to:

1) store the data and

2) provide a standardized method for retrieving

or changing the data, and finally, the userswho turn the data into information


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A database might be as complex and

demanding as an account tracking system

used by a bank to manage the constantlychanging accounts of thousands of bank

customers, or it could be as simple as a

collection of electronic business cards on

your laptop


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The important thing is that a database

allows you to store data and get it or

modify it when you need to easily and

efficiently regardless of the amount of data

being manipulated


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Elmasri says:

A Database (DB) is collection of related

data - with the following properties:

A DB has some relevant meaning

A DB is designed, built and populated with data

for a specific purpose

A DB represents some aspect of the real world


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Kroenke says:

An integrated, self-describing collection of

relateddata

Integrated: Data is stored in a uniform way, typically all in one

place (a single physical computer for example)

Self-Describing: A database maintains a description of the data

it contains (Catalog)

Related: Data has some relationship to other data. In aUniversity we have students who take courses taught by

professors


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We can also say that the database is a model of what theusers perceive

Three main categories of models:

User Models: How users perceive the world and / or thebusiness

Logical Models: Represent the logic of how a businessoperates. For example, the relationship between differententities and the flow of data through the organization. Based on

the User's modelPhysical Models: Represent how the database is

actually implemented on a computer system. This is based onthe logical model


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What is in a Database?What is in a Database?

A database contains information about

a particular enterprise or a particular

application E.g., a database for an enterprise may

contain everything needed for the planning

and operation of the enterprise: customerinformation, employee information, product

information, sales and expenses, etc


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You dont have to be a company to use a database:

you can store your personal information, expenses,

phone numbers in a database (e.g., using Access on

a PC) As a matter of fact, you could store all data

pertinent to a particular purpose in a

database

This usually means that a database stores data that

are related to each other


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Examples

Credit card shopping it automatically checks

the balance and updates the amount in the card

after deduction

Scanner used to read Universal Product Code

Online Air Reservation System


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Example Soft wares

Traditionally, databases ran on large, powerfulmainframes for business applications. You willprobably have heard of such packages as

Oracle orSQL ServerHowever with the advent of small, powerful

personal computers, databases have becomemore readily usable by the average computer

user. Microsoft's Access and Borland'sParadox are two popular PC-based enginesaround


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Database System

Database system is basically a

computerized record keeping system; that

is a computerized system whose overallpurpose is to maintain information and to

make that information available on

demand


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A collection of software programs that are

used to define, construct, maintain and

manipulate data in a database


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Who Needs Database SystemsWho Needs Database Systems

Corporate databases

Web datamanagement

Typical Applications:Personnel management

Inventory and purchase orderInsurance policies

Typical Applications

Web page managementPersonalize web pages


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The user of the system will be given facilities

to perform a variety of operations on such

files :

Adding new empty files to database Inserting new data into existing files

Retrieving data from existing files

Updating data in existing files

Deleting data from existing files

Removing existing files, empty or otherwise, from the

database


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Now we will refer these files in the

database as Tables

The rows of such tables are referred to as

Records of that file/table

The columns can be regarded asrepresenting the Fields


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DBMS

All access to the database is controlled by a

sophisticated software called Data Base

Management System

Software that defines a database, stores the

data, supports a query language, produces

reports, and creates data entry screens

Microsoft Accessis an example of DBMS


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What is the goal of real DBMS

Electronic record-keeping

Fast and convenient access to information


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Example

E.g. students, taking classes, obtaining

grades;

Find my GPA


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Solution: paper-based

Advantages?

Disadvantages?


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Advantages? cheap

Disadvantages?


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Advantages? cheap

Disadvantages?

no queries no sharing

large physical foot-print


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Next solution

computer-based (flat) files +

C (Java, ...) programs to access them

e.g., one (or more) UNIX/DOS files,

with student records and their courses


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Next solution

your layout for the student records?


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Next solution


(eg., comma-separated values CSV)

1,Sarfraza,Chattha,Lahore

50,Tompson,Peter,NewYork

151,Shazia,Qayyum,Lahore


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Next solution


(many other layouts are also possible)eg.:

Smith,John,1,London

Tompson,Peter,234Atkinson,Mary,345,03009449449,Lahore


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Problems?

Inconvenient access to data (need C++

expertise, plus knowledge of file-layout)

Data redundancy

Integrity problems


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Problems? (contd)

...

Concurrent-access anomalies

Security problems


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Problems? (contd)

why?

because of two main reasons: file-layout description is buried within the C

programs and

there is no support for transactions (concurrency

and recovery)

DBMS handle exactly these two problems


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Main Products

Commercial

Oracle

IBM/DB2

MS SQL-Server

Sybase

InformixMS Access


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Company Product RemarksOracle Oracle 8i, 9i, etc. Worlds 2nd largest software company CEO,

Larry Ellison, worlds 2nd richest

IBM

DB2, Universal ServerWorlds 2nd largest after Informix acquisition

Microsoft Access, SQL Server Access comes with MS Office

Sybase Adaptive Server CEO John Chen, grown up in HK

Informix Dynamic ServerAcquired by IBM in 2001

Big Names in Database SystemsBig Names in Database Systems

lecture 2 database database system dbms

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