Ch01 - 6th Edition (1)

8/20/2019 Ch01 - 6th Edition (1)

1/24

Chapter 1

Introduction to Databases

Pearson Education © 2014

8/20/2019 Ch01 - 6th Edition (1)

2/24

Chapter 1 - Objectives

Some common uses of database systems.Characteristics of file-based systems.Problems with file-based approach.

Meaning of the term database.Meaning of the term DatabaseManagement System (DBMS).


8/20/2019 Ch01 - 6th Edition (1)

3/24

Chapter 1 - Objectives

Typical functions of a DBMS.Major components of the DBMSenvironment.

Personnel involved in the DBMSenvironment.History of the development of DBMSs.Advantages and disadvantages of DBMSs.


8/20/2019 Ch01 - 6th Edition (1)

4/24

Examples of Database

ApplicationsPurchases from the supermarketPurchases using your credit cardBooking a holiday at the travel agents

Using the local libraryTaking out insuranceRenting a videoUsing the InternetStudying at university


8/20/2019 Ch01 - 6th Edition (1)

5/24

File-Based Systems

Collection of application programs thatperform services for the end users (e.g.reports).

Each program defines and manages itsown data.


8/20/2019 Ch01 - 6th Edition (1)

6/24

File-Based Processing


8/20/2019 Ch01 - 6th Edition (1)

7/24

Limitations of File-Based

ApproachSeparation and isolation of dataEach program maintains its own set of data.Users of one program may be unaware of

potentially useful data held by other programs.

Duplication of dataSame data is held by different programs.Wasted space and potentially different valuesand/or different formats for the same item.


8/20/2019 Ch01 - 6th Edition (1)

8/24

Limitations of File-Based

ApproachData dependenceFile structure is defined in the program code.

Incompatible file formatsPrograms are written in different languages,and so cannot easily access each other’s files.

Fixed Queries/Proliferation of application

programsPrograms are written to satisfy particularfunctions.Any new requirement needs a new program.


8/20/2019 Ch01 - 6th Edition (1)

9/24

Database Approach

Arose because:Definition of data was embedded inapplication programs, rather than beingstored separately and independently.

No control over access and manipulation ofdata beyond that imposed by applicationprograms.

Result:the database and Database ManagementSystem (DBMS).


8/20/2019 Ch01 - 6th Edition (1)

10/24

Database

Shared collection of logically related data(and a description of this data), designed tomeet the information needs of anorganization.

System catalog (metadata) providesdescription of data to enable program–dataindependence.

Logically related data comprises entities,attributes, and relationships of anorganization’s information.


8/20/2019 Ch01 - 6th Edition (1)

11/24

Database Management System(DBMS)

A software system that enables users todefine, create, maintain, and controlaccess to the database.

(Database) application program: acomputer program that interacts withdatabase by issuing an appropriaterequest (SQL statement) to the DBMS.


8/20/2019 Ch01 - 6th Edition (1)

12/24

Database Management System(DBMS)


8/20/2019 Ch01 - 6th Edition (1)

13/24

Database Approach

Data definition language (DDL).Permits specification of data types,structures and any data constraints.

All specifications are stored in the database.

Data manipulation language (DML).General enquiry facility (query language) of

the data.


8/20/2019 Ch01 - 6th Edition (1)

14/24

Database Approach

Controlled access to database mayinclude:

a security system

an integrity systema concurrency control systema recovery control systema user-accessible catalog.


8/20/2019 Ch01 - 6th Edition (1)

15/24

Views

Allows each user to have his or her ownview of the database.

A view is essentially some subset of thedatabase.


8/20/2019 Ch01 - 6th Edition (1)

16/24

Views - Benefits

Reduce complexityProvide a level of securityProvide a mechanism to customize the

appearance of the databasePresent a consistent, unchanging pictureof the structure of the database, even ifthe underlying database is changed


8/20/2019 Ch01 - 6th Edition (1)

17/24

Components of DBMS Environment


8/20/2019 Ch01 - 6th Edition (1)

18/24


HardwareCan range from a PC to a network ofcomputers.

SoftwareDBMS, operating system, network software (ifnecessary) and also the application programs.

Data

Used by the organization and a descriptionof this data called the schema.


8/20/2019 Ch01 - 6th Edition (1)

19/24


ProceduresInstructions and rules that should be applied tothe design and use of the database and DBMS.

People


8/20/2019 Ch01 - 6th Edition (1)

20/24

Roles in the DatabaseEnvironment

Data Administrator (DA)Database Administrator (DBA)Database Designers (Logical and

Physical)Application ProgrammersEnd Users (naive and sophisticated)


8/20/2019 Ch01 - 6th Edition (1)

21/24

History of Database Systems

First-generationHierarchical and Network

Second generationRelational

Third generation

Object-RelationalObject-Oriented


8/20/2019 Ch01 - 6th Edition (1)

22/24

Advantages of DBMSs

Control of data redundancyData consistencyMore information from the same amount

of dataSharing of dataImproved data integrityImproved securityEnforcement of standardsEconomy of scale


8/20/2019 Ch01 - 6th Edition (1)

23/24

Advantages of DBMSs

Balance conflicting requirementsImproved data accessibility andresponsiveness

Increased productivityImproved maintenance through dataindependenceIncreased concurrencyImproved backup and recovery services


8/20/2019 Ch01 - 6th Edition (1)

24/24

Disadvantages of DBMSs

ComplexitySizeCost of DBMS

Additional hardware costsCost of conversionPerformanceHigher impact of a failure


Ch01 - 6th Edition (1)

Documents