01 - Introduction to Database

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INTRODUCTION TO

DATABASE

Semester 1 2013/2014

At the end of this module, students should be able to define and

identif the followin s:

Learning Objective Some common uses of database systems (db).

Characteristics, problems and differences between file-based

approach and db approach.

Meaning of terms - db, Database Management System

(DBMS), db application system, db system

Personnel involved in the DBMS environment.

Advantages and disadvantages of DBMSs

Three-Level ANSI-SPARC Architecture


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Introduction The database is now such an integral part of our day-

to-da life that often we are not aware we are usinone

We will examine some applications of databasesystem

We will use some terminology in this chapter : database : a collection of related data

DBMS (database management system) : the software that

manages & controls access to the database database application : a program that interacts with the

database at some point in its execution

database system : a collection of application programs thatinteract with the database along with the DBMS anddatabase itself

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DB SYSTEM

Overview of DB System

. . . .

. . . .

. . . .

4

DB

APPLICATIONS

DBMSDB

. . . .

USER


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Traditional File Based System An early attempt to computerize the manual filing

Definition

Collection of application programs that performservices for the end users (e.g. reports). Each

program defines and manages its own data.

Works well while the number of items to be stored is

small. However, it breaks down when we have tocross-reference or process the information in the files.

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File Based Processing

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File Based Processing

Figure shows each department accessing their own

for them.

Each set of departmental application programs

handles data entry, file maintenance, and the

generation of a fixed set of specific reports.

records are defined in the application code

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Limitations of File-Based Approach

Se aration and isolation of data Each program maintains its own set of data.

Users of one program may be unaware of potentially

useful data held by other programs.

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Same data is held by different programs.

Wasted space and potentially different values and/or

different formats for the same item.


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Data dependence

Limitations of File-Based Approach

.

Changes to an existing structure are difficult to make

Incompatible file formats Programs are written in different languages, and so cannot easily

access each others files.

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programs

Programs are written to satisfy particular functions.

Any new requirement needs a new program.

Database Approach

The limitations of the file-based approach can

1. Definition of data was embedded in application

programs, rather than being stored separately andindependently.

2. No control over access and manipulation of data

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beyond that imposed by application programs.

Result, a new approach was required:-

the database and Database Management System

(DBMS).


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The Database Definition :

Shared collection of logically related data (and a descriptiono s a a , es gne o mee e n orma on nee s o anorganization.

A database is also defined as a self-describingcollection of integrated records The description of the data is known as the system

catalogue (metadata) to enableprogramdata independence.

The definition of data is separated from the application

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program. The users of an object only see the external definition and

unaware of how the object is defined and how it functioned

Logically related data comprises entities, attributes,andrelationships of an organizations information.

DBMS is the software that interacts with the users

Database Management System

(DBMS)

Definition - A software system that enables users todefine, create, and maintain the database and that

provides controlled access to this database.1. Define using Data Definition Language (DDL)

2. Create insert, update, delete & retrieve data using DataMani ulation Lan ua e DML

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3. Controlled accessed security, integrity, concurrencycontrol, recovery & user-accessible catalog

Example of DBMS Microsoft Access, MicrosoftSQL Server, Oracle, Sybase and etc.


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Data definition language (DDL).

Database Management System

(DBMS)

Permits specification of data types, structures and any data

constraints.

All specifications are stored in the database.

Data manipulation language (DML).

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General enquiry facility (query language) of the data.

Using Structured Query Language (SQL) to produce required

information.-

Database Application Programs

A computer program that interacts with the database

by issuing an appropriate request (typically an SQL

statement) to the DBMS Users interact with the database through a

number of application programs (used to create &

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information) written in some programminglanguage


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Database Application Programs Figure shows each department using their

through the DBMS. Each set of departmental application programs

handles data entry, file maintenance, and thegeneration of a fixed set of specific reports.

The physical structure & storage of the data are now

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A view mechanism. Provides users with only the data they want or

need to use.

DATABASE SYSTEMApplication Program

Database Application Programs

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Components of DBMS

Environment

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Roles in the Database Environment

responsible for the management of the data

resourceDatabase planning

Development and maintenance of standards,

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po c es, proce ures

Conceptual/logical database design


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Database Administrator (DBA)


responsible for the physical realization of thedatabase

Physical database design andimplementation

Maintenance of operational control

Ensuring satisfactory performance ofapplications for users

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Database Designers (Logical and


Physical)

Logical : is concerned with identifying the

data, the relationships between the data, &

the constraint on the data that is to be stored

Physical : decides how the logical database

design is to be physically realized

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pp ca on rogrammers

build the application programs that provide

the required functionality for the end-users

End Users

naive and sophisticated

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File-based ApproachLimitation of File Based Approach :

Separation and isolation of data

Duplication of data

Data dependence

Incompatible file formats

Fixed Queries/Proliferation of

application programs

Database ApproachAdv antag es of Dat abase Appro ach : Control of data redundancy

Data consistency

More information from the same amount

of data

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Sharing of data

Improved data integrity & s ecurity

Improved data accessibility and

responsiveness

Increased productivit y

Improved maintenance through data

independence

Increased conc urrency

Improved backup and recovery services


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Three-Level Architecture

All DBMS are built based on the 3-Level

Architecture

All users should be able to access same

data.

A users view is immune to chan es made

in other views.

Users should not need to know physical

database storage details. 23

DBA should be able to change database


s orage s ruc ures w ou a ec ng eusers views.

Internal structure of database should beunaffected by changes to physical aspects

.

DBA should be able to change conceptualstructure of database without affecting allusers.

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ANSI-SPARC Three-Level Architecture

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External Level


Users views of the database.

Describes that part of database that isrelevant to a particular user.

Conceptual Level

Community view of the database.

Describes what data is stored in database

and relationships among the data.26


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Internal Level


Physical representation of the database

on the computer.

Describes how the data is stored in the

database.

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Physical Level


Managed by OS under directions of DBMS

Access methods varies - may follow fully OS

access methods or its own file organizations

with some basic OS access methods

mp ementat on o sequenc ng

How fields of internal records are stored on disks

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29Pearson Education 2009

Data Independence

Referring to mapping between external,

Logical Data Independence

Refers to immunity of external schemas tochanges in conceptual schema.

. .

removal of entities).

Should not require changes to external schema or

rewrites of application programs.30


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Data Independence

Ph sical Data Inde endence

Refers to immunity of conceptual schema to

changes in the internal schema.

Internal schema changes (e.g. using different

file organizations, storage structures/

devices).

Should not require change to conceptual or

external schemas.31

Data Independence and the ANSI-SPARC


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Summary

Importance of databases

Database approach VS file-based approach

Important terms in database fields

Database, database applications, databasesystems, DBMS

-levels and associations with data

independence

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Documents

01 - Introduction to Database