lec-1 introduction to database systems[1]

7/29/2019 Lec-1 Introduction to Database Systems[1]

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Text Book

1. Ramakrishna R and J Gerke ;

McGrawHill Reference Book

1. R Elmasri & S B Navate;


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Data: raw facts Being stored and retrieved

Not to be processed to reveal their meaning to theuser

Information: processed data

Key to good decision making

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A set of information held in acomputer

One or more large structured sets ofpersistent data, usually associatedwith software to update and query thedata

A collection of data arranged for easeand speed of search and retrieval

Introduction to Database Systems


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7/42Introduction to Database Systems

Data: Known facts that can be recorded and

that have implicit meaning

Database: Collection of related data

Ex. the names, telephone numbers and

addresses of all the people you know

Database Management System: A

computerized record-keeping system


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Library catalogues Medical records

Bank accounts

Stock market data

Personnel systems

Product catalogues

Telephone directories

Train timetables Airline bookings

Credit card details

Student records

Customer histories

Stock market prices

Discussion boards

and so on



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Network Data Model

(mid 70s)File System

(before 70s)

Hybrid model

(mid 80s)

Relational model

(late 80s)

Object-oriented

model (mid 90s)

Object-relational

model (late 90s)

data

modeling

capacity

data

management

facilities

* adapted from the material in http://www.ktdata.co.kr/ktdata/kthome7/zeus_5.htm


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Database is a collection of data describing objects and theirrelationships

However a DBMS is software designed to assist in

maintaining and utilizing large collection of data.

Database Management System = DBMS

A collection of files that store the data

A big C program written by someone else that accesses and

updates those files for you

Relational DBMS = RDBMS

Data files are structured as relations (tables)


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A very large, integrated collection of data.

Models real-world enterprise.

Entities (e.g., students, employee)Attributes (e.g., student-roll,name,age,address,class

etc.)

Relationships (e.g., Teacher is teaching student)

A Database Management System (DBMS)is asoftware

package designed to store and manage databases.


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Database Management System (DBMS): software

system (collect of software) help to manage the data

contentsManages Database structure

Controls access to data

Contains query language

Application software DBMS Database


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Goals of a Database Management System:

To provide an efficient as well as a convenient environment for

accessing data in a database

Enforce information security: database security, concurrency

control, crash recovery

It is a general purpose facility for:

Defining database

Constructing database

Manipulating database


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Backend for traditional database applications

Backend for large Websites

Backend for Web services

Amazon


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Sure we can! Start by storing the data in files:

students.txt courses.txt professors.txt

Now write C or Java programs to implementspecific tasks

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Enroll Ram in BBA108:

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Read students.txt

Read courses.txt

Find&update the record Ram

Find&update the record BBA108Write students.txt

Write courses.txt

Write a C/Java program to do the following:


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Large data sets (say 50GB)

Simultaneous access by many users Lock students.txt what is the problem ?

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Read students.txtRead courses.txtFind&update the record Mary JohnsonFind&update the record CSE444Write students.txtWrite courses.txt

CRASH !


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program-1

data description-1

program-2

data description-2

program-3

data description-3

File-1

File-2

File-3

Application program-1with data semantics



Description

Manipulation

Control

Queries Database

File System approach

DBMS approach


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Data Raw Facts

Field

Group of characters with specific meaning Record

Logically connected fields that describe aperson, place, or thing

File and file folder Collection of related records


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fieldrecord


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Figure 1.5


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Each application must move large datasetsbetween main memory and secondary storage(must deal with, e.g., buffering, page-oriented

access, etc).

Each application must deal with some methodof identifying all data items in case the available

addressing mode is not sufficient (e.g., 32-bitaddressing cannot directly access more than4GB).


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advantages disadvantages

FMS

Simpler to use Less expensive

Typically no multi-user access Limited to smaller databases

Limited functionality

Decentralization of data

Redundancy and integrity issues

Crash Recovery

DBMS Greater flexibility

Greater processing power

Ensures data integrity

Supports simultaneousaccess

Provides backup and

recovery controls

Advanced security

Supports Transaction

Difficult to learn

Packaged separately from the

OS

Slower processing speeds Requires skilled administrators

Expensive


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33Data files

Database server

(someone elses

C program)Applications

connection

(ODBC, JDBC)

Two tier system or client-server


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Many computingapplications deal withlarge amounts of

information

Database systemsgive a set of tools for

storing, searchingand managing thisinformation

Databases are a coretopic in computerscience and IT

Basic concepts andskills with databasesystems are part ofthe skill set you will

be assumed to haveas a BBA graduate



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A large amount of data,

Concurrent access by many users,

Fast access,

Consistent data update, Role-based security,

Robust against hardware failures and

OS crashes.



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*Application programs no details of datarepresentation & storage

* High-quality data compression schemes,

* Fast data retrieval and search algorithms.

* Programs can prevent invalid queries from

being executed,

* Access control can be enforced.



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* The DBA can optimize the organizationof the data to facilitate its uses.



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Advantages of DBMS


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Slow Response- need to update data in real time.

- Can be slow & complex to extract data for reports

Application may need to manipulate the data in waysnot supported by query Language. Eg flexible analysisof text data

intoday's scenario



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Open source Databases

MySQL

PostgreSQL

Commercial Databases

MS SQL Server MS Access

ORACLE

DB2

Informix

lec-1 introduction to database systems[1]

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