ETEC 100ETEC 100 Information Information TechnologyTechnology

Lecture Introduction to database

Learning ObjectivesLearning Objectives

Define and understand the following Define and understand the following terms: terms: data, information, database, database data, information, database, database management system (DBMS), database management system (DBMS), database system, metadatasystem, metadata

Compare and contrast conventional file Compare and contrast conventional file systems and database systems. Identify systems and database systems. Identify advantages of database approach over advantages of database approach over traditional file systemstraditional file systems

What is database? Database:Database: An An organizedorganized collection of collection of logically relatedlogically related data data

Data:Data: Known facts that could be recorded and stored on computer Known facts that could be recorded and stored on computer media media

Facts could be in any format: text, graphics, images…Facts could be in any format: text, graphics, images…

Information:Information: Processed data that could be used to increase the Processed data that could be used to increase the knowledge of the userknowledge of the user

Closely related to data, but differentClosely related to data, but different View data as “raw material” and information as “intermediate product”View data as “raw material” and information as “intermediate product” The final product is “knowledge”The final product is “knowledge”

Data, Information and Knowledge

Data Information

Taurus

Ann

a B

erge

r

John Smith

Ted Martin

Amex G

old

50,0

00

234

wirelessB.A.

A. Berger M. JonesT. MartinJ. Smith

50,00046,800 29,20075,500

ShoesScarvesJewelry

Groceries

shoes

MoUQty

IncomeEducation

®

Some of the images above come from a presentation

given by:

Database Queries ?

Knowledge &Customer Insight

A. Berger is mostlikely to buy new product

T. Martin is profitablecustomer and is likely to switch carriers

Databases Databases

Interact with DBs many times in a dayInteract with DBs many times in a day Database processing integral part of many Database processing integral part of many

businessesbusinesses Keep track of things (what sort of things?)Keep track of things (what sort of things?)

History of data collection History of data collection methodsmethods

Manual SystemManual System File SystemFile System Database SystemDatabase System

Manual Filling SystemsManual Filling Systems

Before computerBefore computer: Manual Filing Systems: Manual Filing Systems Still used in many everyday activitiesStill used in many everyday activities Usually organize data in a logical wayUsually organize data in a logical way Ex;bills……..Ex;bills……..

ProblemsProblems with Manual Filling Systems with Manual Filling Systems Small –scaleSmall –scale Hard to analyze: ‘ How many students enrolled in Hard to analyze: ‘ How many students enrolled in

MIS ?MIS ?

Traditional File-BasedTraditional File-Based processing processing

Application programs were written Application programs were written specifically for the data file structurespecifically for the data file structure that was to be used, so:that was to be used, so:

A change in the data file structure A change in the data file structure required change in an application required change in an application program(s) that needed that dataprogram(s) that needed that data

File Processing Systems: An exampleFile Processing Systems: An example

Data Entry File

Management Programs Data Files

File Report Programs

End Users

Separated systems, separated files, separated data

Both file management programs and file report programs have describe WHAT data to write / read and HOW to do that

File Processing Systems: ProblemsFile Processing Systems: Problems

Isolation of Data/ Limited Data Sharing

Isolation between departments file systems Isolation in a department file system:

Duplication of Data

Duplicated data waste storage space

Duplicated data result in loss of data integrity

Lack of Data Independence If we change the data type of address from 40 characters to 41

characters, all related programs have to change accordingly

Database Systems: Basic TermsDatabase Systems: Basic Terms DatabaseDatabase:: An organized collection of logically related dataAn organized collection of logically related data

Database Management Systems (DBMS):Database Management Systems (DBMS): A A softwaresoftware package package to facilitate the creation and maintenance of a to facilitate the creation and maintenance of a databasedatabase. .

Database system:Database system: a a computerized record-keeping systemcomputerized record-keeping system, , containing containing databasedatabase and and DBMSDBMS as well as some other as well as some other components.components.

Four components: Users, Software, Hardware, DataFour components: Users, Software, Hardware, Data

Database Systems: Basic TermsDatabase Systems: Basic Terms

Database

DBMS

“How” to get

Application Programs

“What” to get

End usersinteract

Application Programmers

Database Administrators

Database Designers

develop

maintain

design

Software

Users

Data

Database Systems: AdvantagesDatabase Systems: Advantages

Data are stored in a central repository, managed by Data are stored in a central repository, managed by DBMSDBMS

Data sharing is easyData sharing is easy Reduce duplication to minimum: Reduce duplication to minimum: oneone table for each entity table for each entity Inconsistency can be avoided to some extent by enforcement Inconsistency can be avoided to some extent by enforcement

of of integrity constraintsintegrity constraints

Metadata offers data abstractionMetadata offers data abstraction Data independence: If format needs to be changed, simply Data independence: If format needs to be changed, simply

update the metadata. Application programs are not affectedupdate the metadata. Application programs are not affected Structural independence: similar to the above Structural independence: similar to the above

Data Elements in a DatabaseData Elements in a Database

User User datadata (files) (files) relations in a table format (e.g. Relational Database)relations in a table format (e.g. Relational Database)

MetadataMetadata (systems tables) (systems tables)data about data, data dictionarydata about data, data dictionarymeaning of terms, description of structure etc.meaning of terms, description of structure etc.

IndexesIndexes (overhead data) (overhead data)improves performance and accessibilityimproves performance and accessibility

Application MetadataApplication Metadata structure & format of forms, reports, & queries etc.structure & format of forms, reports, & queries etc.

Database Development ProcessDatabase Development Process

Requirement Analysis Requirement Analysis

Conceptual Design

Logical Design

Physical Design

Implementation

Maintenance

Database Development ProcessDatabase Development Process

Requirements AnalysisRequirements Analysis Collect and Analyze the requirements of the users.Collect and Analyze the requirements of the users.

Conceptual DesignConceptual Design Design a Design a conceptualconceptual model, e.g., ER model. model, e.g., ER model.

Logical DesignLogical Design Translate the conceptual model into the Translate the conceptual model into the logicallogical model model NormalizationNormalization..

Physical DesignPhysical Design Define the database and write application programsDefine the database and write application programs..

ImplementationImplementation Write, test, and install programs that process the databaseWrite, test, and install programs that process the database

MaintenanceUseMaintenanceUse maintain, and maintain, and “tune”“tune” the database the database

Relational DatabaseRelational Database

A A relational databaserelational database is one in which the is one in which the data consists of a collection of tables data consists of a collection of tables related to each other through common related to each other through common values.values.

The two most prominent characteristics of The two most prominent characteristics of a relational database are a relational database are data stored in tablesdata stored in tables relationships between tablesrelationships between tables

TableTable

RelationRelation Two-dimensional tableTwo-dimensional table Rows are Rows are tuplestuples Columns are Columns are attributesattributes

Equivalent Terms:Equivalent Terms:

Characteristics of a Characteristics of a relationrelation

a a relationrelation has a has a unique nameunique name within same within same DBDB each each cellcell contains contains one single valueone single value each each attributeattribute within a given relation has a within a given relation has a distinct distinct

namename valuesvalues of an attribute are from the of an attribute are from the same domainsame domain orderorder of attributes has of attributes has no significanceno significance orderorder of of rows rows has has no significanceno significance no duplicateno duplicate rowsrows

KeyKey “a group of one or more attributes (columns) that uniquely identifies a tuple (row)”

Relational Database KeysRelational Database Keys Candidate keyCandidate key Primary keyPrimary key: candidate key selected to : candidate key selected to

uniquely uniquely identify all table rowsidentify all table rows Foreign keyForeign key: attributes(s) in one table whose : attributes(s) in one table whose

values must match primary values must match primary key in key in another tableanother table

RelationshipsRelationships

Referential Referential IntegrityIntegrity RRuleule

IIf f a foreign key existsa foreign key exists in a relation, in a relation,

eithereither

the foreign key value the foreign key value must match a candidate key must match a candidate key valuevalue of some tuple in its home relation of some tuple in its home relation

oror

the foreign key the foreign key valuevalue must be wholly nullmust be wholly null

TThereforeherefore:-:- if B references A if B references A then Athen A must existmust exist

Schema Schema

A A schemaschema is an abstract representation of is an abstract representation of database entities and objects. A schema database entities and objects. A schema helps us design a database helps us design a database diagrammatically before we start creating diagrammatically before we start creating it. it.

Schema (cont.)Schema (cont.)

QueryQuery

Requests for information from a database are Requests for information from a database are made in the form of a made in the form of a queryquery. .

The set of rules for constructing queries is The set of rules for constructing queries is known as a known as a query languagequery language. .

query language called query language called SQLSQL (structured query (structured query language) language)

For example, the query -requests all recordsfrom For example, the query -requests all recordsfrom customer table in which the NAME field is customer table in which the NAME field is SMITH and the AGE field is greater than 35. SMITH and the AGE field is greater than 35.

SQLSQL (structured query language) (structured query language)

For example, the query -requests all For example, the query -requests all recordsfrom recordsfrom customercustomer table in which the table in which the NameName field is SMITH and the field is SMITH and the AgeAge field is field is greater than 35. greater than 35.

SELECT ALL SELECT ALL

FROM CustomerFROM Customer

WHERE Name = "SMITH" and age > 35 WHERE Name = "SMITH" and age > 35