copyright oracle corporation, 1999. all rights reserved. 11 ® introduction to entities,...

Copyright Oracle Corporation, 1999. All rights reserved.

1111

®

Introduction to Entities, Attributes, and Relationships

Introduction to Entities, Attributes, and Relationships

Section 02 – Lessons 1,2,3 Section 02 – Lessons 1,2,3

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1-1-22 Copyright Oracle Corporation, 1999. All rights reserved.®

OverviewOverview

• Why conceptual modeling?

• Introduction of the Key role players:

– Entities

– Attributes

– Relationships

• Why conceptual modeling?

• Introduction of the Key role players:

– Entities

– Attributes

– Relationships


Why Create a Conceptual Model?Why Create a Conceptual Model?

• It describes exactly the information needs of the It describes exactly the information needs of the businessbusiness

• It facilitates discussionIt facilitates discussion

• It helps to prevent mistakes, misunderstandingIt helps to prevent mistakes, misunderstanding

• It forms important “ideal system” documentationIt forms important “ideal system” documentation

• It forms a sound basis for physical database It forms a sound basis for physical database designdesign

• It is a very good practice with many practitionersIt is a very good practice with many practitioners

• It describes exactly the information needs of the It describes exactly the information needs of the businessbusiness

• It facilitates discussionIt facilitates discussion

• It helps to prevent mistakes, misunderstandingIt helps to prevent mistakes, misunderstanding

• It forms important “ideal system” documentationIt forms important “ideal system” documentation

• It forms a sound basis for physical database It forms a sound basis for physical database designdesign

• It is a very good practice with many practitionersIt is a very good practice with many practitioners


Between Dream and Reality...Between Dream and Reality...


Dream and Reality - ActivityDream and Reality - Activity

Directions:

• Working in pairs, one student describes his/her "dream house" while the other student attempts to draw it. The pairs can discuss specific details but, the student describing the house is not allowed to see what is being drawn until after time is called.

Assessment:

• Ask volunteer student pairs to describe the discrepancies between what they thought was being described and what was actually drawn.

Directions:

• Working in pairs, one student describes his/her "dream house" while the other student attempts to draw it. The pairs can discuss specific details but, the student describing the house is not allowed to see what is being drawn until after time is called.

Assessment:

• Ask volunteer student pairs to describe the discrepancies between what they thought was being described and what was actually drawn.


Entity Relationship ModelingEntity Relationship Modeling

• Models business,not implementation

• Is a well-established technique

• Has a robust syntax

• Results in easy-to-read diagrams…

...although they maylook rather complex at first sight

• Models business,not implementation

• Is a well-established technique

• Has a robust syntax

• Results in easy-to-read diagrams…

...although they maylook rather complex at first sight

SUPPLIER# SUPPLIER CODEo EMAIL* APPROVED* REFERENCE

OTHER ORGANIZATION

ORGANIZATIONo EMAIL* NAMEo POSTAL CODEo REGIONo STREETo TOWNo TELEPHONE NUMBERo CONTACT NAMEo CONTACT EXTENSION

MEMBERSHIP TYPE# CODE* DESCRIPTION* DISCOUNT PERCENTAGEo STANDARD FEE

MEMBERSHIP PERIOD# START DATEo ACTUAL FEE PAID

MEMBERSHIP# NUMBERo TERMINATION REASONo TERMINATION DATE

EMPLOYEE* POSITION* LAST NAMEo FIRST NAMEo OTHER INITIALSo EMAIL

BOOKING* BOOK DATEo EXPIRE DATEo NOTIFY DATEo RESERVE DATEo STAFF REMARKS

RENTAL ITEM# LINE NO* RENTAL PERIOD* PRICE PAIDo RETURN DATEo STAFF REMARKS

RENTAL* RENTAL DATEo STAFF REMARKSo COMPLETED

COPY* ACQUIRE DATE* PURCHASE COST* SHELF CODEo CONDITIONo CUSTOMER REMARKS...

REVIEW# SEQUENCE* ARTICLE* HOTo AUTHORo URL

PUBLICATION# REFERENCE* TITLEo VOLUMEo ISSUEo PUBLISH DATE

CUSTOMERo EMAIL* DESIGNATION* FIRST NAME* LAST NAMEo OTHER INITIALS* STREET* TOWN* POSTAL CODE* REGIONo HOME PHONEo WORK EXTENSIONo WORK PHONEo PHOTOGRAPHo STAFF REMARKS

CATALOG# REFERENCEo CATALOG DATEo DESCRIPTION

MOVIE* CATEGORYo AGE RATING* DURATION* MONOCHROMEo AUDIOo PREVIEW

GAME* CATEGORY* MEDIUMo MINIMUM MEMORY

TITLE# PRODUCT CODE* TITLEo DESCRIPTION

PRICE LEVEL# CODE* DESCRIPTION

PRICE HISTORY# EFFECTIVE DATE* PRICE* DEFAULT DAYS* OVERDUE RATE

for

used for

of

renewed for

of

the type of

held by

the holder of

held by

the holder of

availablefrom

thedistributor for

requestedagainst the

requestorof

authorized by

responsiblefor

the reservation for

reserved on

for

on

cancelled by

the cancellor of

approved by

responsible for

of

reviewed in

at

applied to

the rental for

fulfilled as

part of

composed of

for

rented on

approved by

responsiblefor

part of

parent organization of

acquired from

the source of

of

available as

for

defined by

managed by

the manager of

in

the source of

in

the source of


Goals of Entity Relationship ModelingGoals of Entity Relationship Modeling

• Capture all required information

• Information appears only once

• Model no information that is derivable from other information already modeled

• Information is in a predictable, logical place

• Capture all required information

• Information appears only once

• Model no information that is derivable from other information already modeled

• Information is in a predictable, logical place


Database TypesDatabase Types

HierarchicalHierarchical

RelationalRelational

NetworkNetwork

ER ModelER Model


EntityEntity

• An Entity is:

– “Something” of significance to the business about which data must be known.

– A name for the things that you can list.

– Usually a noun.

• Examples: objects, events

• Entities have instances.

• An Entity is:

– “Something” of significance to the business about which data must be known.

– A name for the things that you can list.

– Usually a noun.

• Examples: objects, events

• Entities have instances.


Entities and InstancesEntities and Instances

PERSON

PRODUCT

PRODUCT TYPE

EMPLOYMENT CONTRACT

JOB

SKILL LEVEL

TICKET RESERVATION

PURCHASE

ELECTION

PRINTER PREFERENCE

DOCUMENT VERSION

PERSON

PRODUCT

PRODUCT TYPE

EMPLOYMENT CONTRACT

JOB

SKILL LEVEL

TICKET RESERVATION

PURCHASE

ELECTION

PRINTER PREFERENCE

DOCUMENT VERSION

Mahatma Gandhi

2.5 x 35 mm copper nail

nail

my previous contract

violinist

fluent

tonight: Hamlet in the Royal

the CD I bought yesterday

for parliament next fall

…

...

Mahatma Gandhi

2.5 x 35 mm copper nail

nail

my previous contract

violinist

fluent

tonight: Hamlet in the Royal

the CD I bought yesterday

for parliament next fall

…

...


Entities and SetsEntities and Sets

dish washerdish washer

JOB

waiterwaiter

cookcookwaitresswaitress

managermanager

financial controllerfinancial controller

porterporter

piano playerpiano player

• An entity represents a set of instances that are of interest to a particular business.

• An entity represents a set of instances that are of interest to a particular business.


AttributeAttribute

• Also represents something of significance to the business

• Is a single valued property detail of an entity

• Is a specific piece of information that:

– Describes

– Quantifies

– Qualifies

– Classifies

– Specifies

an entity.

• Also represents something of significance to the business

• Is a single valued property detail of an entity

• Is a specific piece of information that:

– Describes

– Quantifies

– Qualifies

– Classifies

– Specifies

an entity.


Attribute ExamplesAttribute Examples

Entity

EMPLOYEE

CAR

ORDER

JOB

TRANSACTION

EMPLOYMENT CONTRACT

Entity

EMPLOYEE

CAR

ORDER

JOB

TRANSACTION

EMPLOYMENT CONTRACT

Attribute

Family Name, Age, Shoe Size,

Town of Residence, Email, ...

Model, Weight, Catalog Price, …

Order Date, Ship Date, …

Title, Description, ...

Amount, Transaction Date, …

Start Date, Salary, ...

Attribute

Family Name, Age, Shoe Size,

Town of Residence, Email, ...

Model, Weight, Catalog Price, …

Order Date, Ship Date, …

Title, Description, ...

Amount, Transaction Date, …

Start Date, Salary, ...


Practice ExercisesPractice Exercises

Complete the following Practice Exercises in class:

• 1-1 "Instance or Entity"

• 1-2 "Guest"

Complete the following Practice Exercises in class:

• 1-1 "Instance or Entity"

• 1-2 "Guest"


RelationshipsRelationships

• Also represent something of significance to the business

• Express how entities are mutually related

• Always exist between two entities (or one entity twice)

• Always have two perspectives

• Are named at both ends

• Also represent something of significance to the business

• Express how entities are mutually related

• Always exist between two entities (or one entity twice)

• Always have two perspectives

• Are named at both ends


Relationship ExamplesRelationship Examples

EMPLOYEES have JOBS

JOBS are held by EMPLOYEES

EMPLOYEES have JOBS

JOBS are held by EMPLOYEES

PRODUCTS are classified by a PRODUCT TYPE

PRODUCT TYPE is a classification for a PRODUCT

PRODUCTS are classified by a PRODUCT TYPE

PRODUCT TYPE is a classification for a PRODUCT

PEOPLE make TICKET RESERVATIONS

TICKET RESERVATIONS are made by PEOPLE

PEOPLE make TICKET RESERVATIONS

TICKET RESERVATIONS are made by PEOPLE


JOB

waiterwaiter

cookcookwaitresswaitress

managermanager

financial controllerfinancial controller

porterporter

piano playerpiano player

Employees have JobsEmployees have Jobs

AhmedAhmed

JillJillAdamAdam

MariaMaria

EMPLOYEEEMPLOYEE

Numerical observation:

• All EMPLOYEES have a JOB

• No EMPLOYEE has more than one JOB

• Not all JOBS are held by an EMPLOYEE

• Some JOBS are held by more than one EMPLOYEE

Numerical observation:

• All EMPLOYEES have a JOB

• No EMPLOYEE has more than one JOB

• Not all JOBS are held by an EMPLOYEE

• Some JOBS are held by more than one EMPLOYEE

ShintaroShintaro dish washerdish washer


Entity Representation in DiagramEntity Representation in Diagram

• Drawn as a “softbox”

• Name singular

• Name inside

• Neither size, nor position has a special meaning

• Drawn as a “softbox”

• Name singular

• Name inside

• Neither size, nor position has a special meaning

EMPLOYEE

TICKETRESERVATION

JOB ASSIGNMENT

JOB

ORDERE

LEC

TIO

N

During design, entities usually lead to tables.


Attributes in DiagramsAttributes in Diagrams

*o

EMPLOYEE Family Name Addresso Birth Dateo Shoe Sizeo Email

JOB Titleo Description

During design, attributes lead to columns.

*

*

*

Mandatory attribute, that is, known and available for every instance

Optional attribute, that is, unknown or unimportant to know for some instances


Jobs are held by one or more employees

An employee has exactly one jobAn employee has exactly one jobhas

Relationship in DiagramsRelationship in Diagrams

EMPLOYEE JOB has

held by

held by

exactly one

one or more

During design, relationships lead to foreign keys.


EMPLOYEE JOB

Two PerspectivesTwo Perspectives

hashas

held byheld by

mandatory:mandatory:mandatory:mandatory: optional:optional:optional:optional:


Every EMPLOYEE has one and only one JOB

One WayOne Way

hashasEMPLOYEE JOB

held byheld by



The Other WayThe Other Way

hashasEMPLOYEE JOB

held byheld by


A JOB may be held by one or more EMPLOYEES


””““EachEach PP split intosplit intomust bemust be

may bemay be one or more Qsone or more QsOne and only one QOne and only one Q

““EachEach P P may be may be split intosplit into one or more one or more Qs Qs””

Reading a Relationship EndReading a Relationship End

P split intosplit into Qpart ofpart of


““EachEach QQ part ofpart of ””must bemust be

may bemay be one or more Psone or more PsOne and only one POne and only one P

““EachEach Q Q must be must be part of part of exactly oneexactly one P P””




““EachEach P P may be may be split intosplit into one or more one or more Qs Qs””

““EachEach Q Q must be must be part of part of exactly oneexactly one P P””




Functions Drive DataFunctions Drive Data

• Business functions are always present.

– Explicit

– Assumed

• Business functions need data.

• An entity, attribute, or relationship may be modeled because:

– It is used by a business function.

– The business need may arise in the near future.

• Business functions are always present.

– Explicit

– Assumed

• Business functions need data.

• An entity, attribute, or relationship may be modeled because:

– It is used by a business function.

– The business need may arise in the near future.


Weather ForecastWeather Forecast

KøbenhavnBremenBerlinMünchenAmsterda

mBruxellesParisBordeaux

1/-5

7/2

3/-1

8/3

5/-3

4/0

4/1

0/-3

January 263

3

3

4

3

2

3

4

****


(Copenhagen)

Bremen

Berlin

(Munich)

Bruxelles

Paris

Bordeaux

Amsterdam

UKUK

FRFR

DEDE

DKDK

CHCH

NLNL

BEBE

ITIT

LULU

IRIR

København

München

(Brussels)


located in

having

referring to

referred in

about

Weather Forecast, a Solution Weather Forecast, a Solution

WEATHER TYPE* Icon* Description

WIND DIRECTION* Icon* Description

COUNTRY* Nameo Geographical Position

CITY* Nameo Geographical Position

FORECAST* Dateo Minimum Temperatureo Maximum Temperatureo Wind Force

referring to

referred in

subject of


Graphical Elements of ER DiagramGraphical Elements of ER Diagram

SubtypeSubtype

##

Unique identifierUnique identifier

ArcArcArcArc

NontransferabilityNontransferabilityNontransferabilityNontransferability

** **o

o

EntityEntity

AttributeAttribute

RelationshipRelationship


SummarySummary

• ER Modeling models information conceptually

• Based on functional business needs

• ER Modeling focuses on “what” a business is doing. Not necessarily the “how”

• Diagrams provide easy means of communication

• Detailed, but not too much

• IN CLASS - Complete the Practice Exercises

• IN CLASS and ONLINE Complete the Quiz for this Chapter.

• ER Modeling models information conceptually

• Based on functional business needs

• ER Modeling focuses on “what” a business is doing. Not necessarily the “how”

• Diagrams provide easy means of communication

• Detailed, but not too much

• IN CLASS - Complete the Practice Exercises

• IN CLASS and ONLINE Complete the Quiz for this Chapter.

copyright oracle corporation, 1999. all rights reserved. 11 ® introduction to entities,...

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