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Chapter1 Introduction

File system vs DBMS

Advantages of DBMS

Storage of data in DBMS

People who work with DBMS


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Data vs. information:Data vs. information:

What is the difference?What is the difference?

What is data?What is data? Data can be defined inData can be defined in

many ways. Informationmany ways. Information

science defines data asscience defines data as

unprocessed information.unprocessed information.

What is information?What is information? Information is data that haveInformation is data that have

been organized andbeen organized and

communicated in a coherentcommunicated in a coherent

and meaningful manner.and meaningful manner.

Data is converted intoData is converted into

information, and information isinformation, and information is

converted into knowledge.converted into knowledge.

Knowledge; informationKnowledge; information

evaluated and organized soevaluated and organized so

that it can be used purposefully.that it can be used purposefully.


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What is the ultimate purpose ofWhat is the ultimate purpose of

a database managementa database management

system?system?

Data

Data Information

Information Knowledge

Knowledge Action

Action

Is to transformIs to transform


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Qualities of information

Accuracy

Timeliness

Relevancy


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What is a databaseWhat is a database

A database is any organized collection of data typically describingA database is any organized collection of data typically describingthe activities of one or more related organizations.the activities of one or more related organizations. ExamplesExamples

A university database might contain information about the followingA university database might contain information about the following

Entities such as students, faculty, courses and classrooms. (entitiesEntities such as students, faculty, courses and classrooms. (entitiesare the basic units used in modeling class of concrete or abstractare the basic units used in modeling class of concrete or abstractobjects.eg: building room, chair .objects.eg: building room, chair .

Relationship between entities such as students enrollment inRelationship between entities such as students enrollment incourses faculty teaching courses and the use of rooms and courses.courses faculty teaching courses and the use of rooms and courses.


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A database is a collection of data which can be used:A database is a collection of data which can be used:

alone, or combined / related to other data to providealone, or combined / related to other data to provideanswers to the users question.answers to the users question.

Some examples of databases you may encounter in yourSome examples of databases you may encounter in yourdaily life are:daily life are: a telephone booka telephone book

airline reservation systemairline reservation system

motor vehicle registration recordsmotor vehicle registration records

papers in your filing cabinetpapers in your filing cabinet

files on your computer hard drive.files on your computer hard drive.


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Why do we need a database?Why do we need a database?

Keep records of our:Keep records of our:

ClientsClients

StaffStaff

VolunteersVolunteers

To keep a record of activities and interventions;To keep a record of activities and interventions;

Keep sales records;Keep sales records;

Develop reports;Develop reports;

Perform researchPerform research


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Tables comprise the fundamental building blocks of any database. If you're familiar withTables comprise the fundamental building blocks of any database. If you're familiar with

spreadsheets, you'll find database tables extremely similar. Take a look at this example of aspreadsheets, you'll find database tables extremely similar. Take a look at this example of a

table sample database:table sample database:

The table above contains the employee information for our organization -- characteristics likeThe table above contains the employee information for our organization -- characteristics like

name, date of birth and title. Examine the construction of the table and you'll find that eachname, date of birth and title. Examine the construction of the table and you'll find that each

column of the table corresponds to a specific employee characteristic (orcolumn of the table corresponds to a specific employee characteristic (orattributeattribute in databasein database

terms). Each row corresponds to one particular employee and contains his or her information.terms). Each row corresponds to one particular employee and contains his or her information.

That's all there is to it! If it helps, think of each one of these tables as a spreadsheet-styleThat's all there is to it! If it helps, think of each one of these tables as a spreadsheet-style

listing of information.listing of information.

Fundamental building blocksFundamental building blocks


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Types of DatabasesTypes of Databases

Non-relational databasesNon-relational databasesNon-relational databases place information in field categories that we create so that information is available forNon-relational databases place information in field categories that we create so that information is available forsorting and disseminating the way we need it. The data in a non-relational database, however, is limited to thatsorting and disseminating the way we need it. The data in a non-relational database, however, is limited to thatprogram and cannot be extracted and applied to a number of other software programs, orprogram and cannot be extracted and applied to a number of other software programs, orother database filesother database fileswithin a school or administrative system. The data can only be "copied and pasted. Example: awithin a school or administrative system. The data can only be "copied and pasted. Example: aspread sheetspread sheet

Relational databasesRelational databasesIn relational databases, fields can be used in a number of ways (and can be of variable length),In relational databases, fields can be used in a number of ways (and can be of variable length),provided that they are linked in tables. It is developed based on a database model that provides forprovided that they are linked in tables. It is developed based on a database model that provides forlogical connections among files (known as tables) by including identifying data from one table inlogical connections among files (known as tables) by including identifying data from one table inanother tableanother table

Note :Note :

Traditional database applications : most of the information is stored and accessed either textual orTraditional database applications : most of the information is stored and accessed either textual ornumericnumeric

Multimedia databases : it stores picture , video clips and sound messagesMultimedia databases : it stores picture , video clips and sound messagesGeographic information systems: it can store and analyze maps, weather data and satellite imagesGeographic information systems: it can store and analyze maps, weather data and satellite images


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Selecting a database system:Selecting a database system:

Need AnalysisNeed AnalysisThe needs analysis process will be specific to your organization but, atThe needs analysis process will be specific to your organization but, at

a minimum, should answer the following questions:a minimum, should answer the following questions:

How many records we will warehouse and for how long?How many records we will warehouse and for how long?

Who will be using the database and what tasks will they perform?Who will be using the database and what tasks will they perform?

How often will the data be modified? Who will make theseHow often will the data be modified? Who will make thesemodifications?modifications?

Who will be providing IT support for the database?Who will be providing IT support for the database?

What hardware is available? Is there a budget for purchasingWhat hardware is available? Is there a budget for purchasing

additional hardware?additional hardware?

Who will be responsible for maintaining the data?Who will be responsible for maintaining the data?

Will data access be offered over the Internet? If so, what level ofWill data access be offered over the Internet? If so, what level of

access should be supported?access should be supported?


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What is database management systemWhat is database management system A DBMS is a collection of programs whichA DBMS is a collection of programs which

provide management of databases , that enables the users to create andprovide management of databases , that enables the users to create and

maintain a database, control access to data contain a query language tomaintain a database, control access to data contain a query language to

retrieve information easilyretrieve information easily

Facilities provided by DBMS :Facilities provided by DBMS :1.1. Creating a file , addition of data , modification of data, creation addition andCreating a file , addition of data , modification of data, creation addition and

deletion of filesdeletion of files

2.2. Retrieving data collectively or selectivelyRetrieving data collectively or selectively

3.3. Data stored can be indexed at the users discretion and directionData stored can be indexed at the users discretion and direction

4.4. Various reports can be generatedVarious reports can be generated5.5. Mathematical function can be performed and the data can be manipulatedMathematical function can be performed and the data can be manipulated

6.6. To maintain data integrity and database useTo maintain data integrity and database use


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DBMS is a general purpose software system that facilitates the processes ofDBMS is a general purpose software system that facilitates the processes of

definingdefining

constructingconstructing

manipulatingmanipulating

sharing databases among various users and applicationssharing databases among various users and applications

DefiningDefining a database involving specifying the data types , structures anda database involving specifying the data types , structures and

constraints for the sat to be stored in the database.constraints for the sat to be stored in the database.

ConstructingConstructing is the process of storing the datais the process of storing the data

ManipulatingManipulating includes such functions such as querying the database to retrieveincludes such functions such as querying the database to retrieve

specific dataspecific data SharingSharing a database allows multiple users and programs to access the databasea database allows multiple users and programs to access the database

concurrently.concurrently.


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DBMS environment

users/ programmers

Applications programs/queries

DBMS software

Software to process

Queries/programs

Software to access stored data

Stored database

(definition)

Stored database


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Characteristics of data in a

database

Shared

Persistence

Validity/integrity/correctness Security

Consistency

Non-redundancy Independence


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Advantages of DBMS

Data independence

Efficient data access

Data integrity and security

Reduction of redundancies

Shared data

Conflict resolution


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Three views of data External view highest level of abstraction as

seen by the user . It describes the part of entiredatabase

Conceptual view : next higher level of abstraction

which is the sum total of users view and describeswhat data are actually stored in the database

Internal level lowest level of abstraction at which

one describes how the data are physically stored

Student name

Student address

Student name : var char

Student address:var char

Student name :varchar:25

Student address:var:25


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Characteristics of a database

approach Self describing nature of a database system (database structure

&constraints)

Insulation between programs and data and data abstraction(program data independence and program operationindependence)

operation function or method

interface of an operation includes operation name and data types

implementation of operation is specified separately and can bechanged without affecting the interface.

Support of multiple views of the data

Sharing of data and multi user transaction processing


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File system versus DBMS

Consider an example of an organization A company has a large collection of data on

employees , department, products, sales and soon

This data is accessed concurrently by severalemployees

Queries about the data needs to be answeredquickly.

Changes made to the data must be consistent Access to certain parts of the data must be

restricted


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Traditional file oriented approach

Traditional file-oriented approach toinformation processing has for eachapplication a separate file and its own set ofpersonal files.

An organization needs1. flow of information across these applications

2. Sharing of data (lacking in Traditionalapproach)

Here programs become dependant on the filesand the files become dependent upon theprograms.


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Some of the drawbacks are

1. Data redundancy

2. Program/data dependency

3. Lack of flexibility

4. To hold all the data which requires a storage device5. There is a need of some methodology of identifying all data items

6. A special program to answer each query

7. Protection and security of data from authorized users

8. Inconsistent changes made by different users accessing the dataconcurrently

9. Ensuring the data is restored to a consistent state if the system crashes10. Operating system provides only a password mechanisms for security


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Storing data in DBMS

User is concerned with some real world

enterprises

An example :

University Database Entities are

students, faculty,, courses.

Data in a university databases describesthese entities and relationships


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Data model uses logical concepts such as objects, theirproperties and their interrelationships. Informally a datamodel is a type of data abstraction that is used toprovide conceptual representation.

A data model is a collection of high level data descriptionconstructs that hide many low level storage details

A DBMS allows a user to define the data to be stored in

terms of a data model

Most of the database management systems today arebased on RELATIONSHIP MODEL


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A semantic data model is a more abstract

high level data model that makes its easier

for a user to have a detailed description of

the data in the enterprise

It is typically built around a data model

with a few basic constructs such as

Relational model.


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People who work with databases

There are a few for creation and use of

databases . They are

1. Database implementors- build DBMS software

2. End users store and use data in a DBMS

3. Application programmers

4. Database administrators


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Database implementors

They work for vendors such as IBM or oracle

End Users

End users are the people whose jobs require access to the database for querying ,updating and generating reports

1. data grows in complexity and volume & care needs for maintaining it.

2. end users use applications written by database application programmers and require lesstechnical knowledge about DBMS software

3. sophisticated users use DBMS by writing their queries

categories of end users1. Casual end users

2. Sophisticated end users (scientists, engineers)

3. Stan alone end users


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Database application programmers

1. They develop packages that facilitate data

access for end users.

2. End users are not computer professionals

using the host language and software tools

that DBMS provide.

(tools report writers, spread sheets andstatistical packages.)


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Database administrator

DBMS is to have a control of data and programsaccessing that data.

Person who has such a control is called the data

base administrator. He administers three levels

Sets up the definition for conceptual view

Specifies external view for various users and

application and is responsible for definition andimplementation of internal level including thestorage structure and access methods


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Changes to any of three levels in underthe control of DBA

Mappings between internal and

conceptual levels and conceptual leveland external level defined by DBA

Ensuring to maintain integrity of the

database Granting permission to end users of the

database


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Summary of functions of DBA

Schema definition

A schema is a logical database description and is drawn as a chart ofthe types of data that are used.

It specifies the name of the entities and attributes and specifies therelationship between them

It is a frame work into which value of the data item can be fitted.

Eg: an information display system gives you the arrival and departuretime at airports, railway system , the schema will remain the samethough the values displayed will change from time to time


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Storage structure and access method

definition

Granting of authorization for data access

Integrity constraint specification

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