Copyright Kathy S. Schwaig, 20011 MBA 8473 Kathy S. Schwaig Information Technology.

Copyright Kathy S. Schwaig, 2001 1

MBA 8473

Kathy S. Schwaig

Information Technology


Database Design StepsDatabase Design Steps

User Requirements

Conceptual Design(E.g. entity-relationship model)

Logical Design(E.g. relational model)

Physical Design(optimize for

performance)


•Database requirements from user

•User view: part of database important to user

•Difficult! Why?

User RequirementsUser Requirements


Conceptual Design Entity-Relationship Model

Conceptual Design Entity-Relationship Model

EntityA “thing” of interest.

May be tangible (employee) or intangible (banking transaction).

E.g. employee, department, manager, customer.

Attributes -- properties or characteristics.

KeyEach entity must be uniquely identified by an attribute

or group of attributes called a key. E.g.: Employee: [EMP#, name, address, phone#]


Order number

Order date

Item number

Quantity Amount

4340 02/08/94 1583 2 1740

Key fieldThis record describes the entity called ORDER and its attributes. The specific values for order number, order date, item number, quantity, and amount for this particular order are the fields for this record. Order number is the key field because each order is assigned a unique identification number.

Order : [Order number , order date, item number, quantity, amount]

Attributes

ENTITY = ORDER


An association between entities.E.g. Managers manage Employees

Cardinalities indicate the number of each entity that may participate in the relationship.One to one (1:1)One to many (1:N)Many to many (N:M)

M:N relationships may have relationship attributes.E.g. Employees assigned-to Projects:[length-of-time]

N : M

RelationshipRelationship


Entity- Relationship DiagramEntity- Relationship Diagram

Each entity represented by a rectangle.

Each relationship represented by a diamond.

Attributes shown in ovals.

Cardinalities next to entities


E-R DiagramE-R Diagram

Student Course

SSN name

address

grade Course#

description

assigned toN M


You have been asked to create a database for a small consulting company. The company wants to keep track of which employees are assigned to which project and what dates they start and stop working on them. An employee can work on more than one project at a time (as any MBA student knows). You also need to keep track of which client sponsors which project(s). Each project usually requires a set of skills so you need to know what skills an employee has and when he or she obtained them. Employees are encouraged to find clients and receive extra compensation for

doing so.

Consulting Company DatabaseConsulting Company Database


Project

Employee

Emp#

Client

Client-Id

sponsors

finds

start-date

end-date

Project#

has

date

acquired

Skill

requires

Skill-

name MN

M

N

l

N

M

N

1

N

assigned to


Entities

Employee : [Emp#, name, address, dob, hourly-rate]

Client : [Client-Id, name, phone, date-signed]

Skill : [Skill-name, description]

Project : [Project#, name, date-began, date-completed]

Consulting Company DatabaseEntity-Relationship Model

Consulting Company DatabaseEntity-Relationship Model


Relationships

Employee finds Client

1 : N

Client sponsors Project

1 : N

Employee has Skill : [date-acquired]

N : M

Project requires Skill

N : M

Employee assigned-to Project : [start-date, end-date]

N : M

Consulting Company DatabaseEntity-Relationship Model (cont’d)

Consulting Company DatabaseEntity-Relationship Model (cont’d)


Relational Data ModelRelational Data Model

One basic construct: the relation.

Relations represent both entities and relationships.

Data Manipulation Language: English-like.

Dominant database structure.

DB2 by IBM

ACCESS by Microsoft

ORACLE


Translate E-R Model into Relational ModelTranslate E-R Model into Relational Model

Each entity represented by an (entity) relation N:M relationship represented by a separate

(relationship) relationKey is concatenation (joining together) of entity

keys.Relationship attributes are non keys.

1:N relationship represented by foreign key, i.e. key of entity on “1” side appears as non key in relation for the entity on the “N” side.


Example: Student-CourseExample: Student-Course

Design a database to keep track of what courses a student takes and the grade he or she receives.

Entities: Student: [SSN, name, address]Course: [Course-Id, description]

Relationships: Student takes Course: [grade] N : M


Student RelationStudent Relation

SSN name address

111-22-3333 M . Tomkins 17 Oak St.

444-71-2222 L.Richardo 22 Tilly Court

795-44-1111 H. M cEnroe 33 Star St.

C ourse-Id description

M B A 401 M gt. Inform ation System s

C IS 481 Strategic System s

C IS 721 D atabase M gt. System s

Course RelationCourse Relation


Takes RelationTakes Relation

SSN Course-Id, grade

795-44-1111 CIS 721 A

444-71-2222 CIS 481 B

111-22-3333 MBA 401 B


Employee : [Emp#, name, address, dob, hourly-rate]

Client : [Client-Id, name, phone, date-signed, emp#]

Project : [Project#, name, date-began, date-completed, client-id]

Skill : [Skill-name, description]

Has-skill : [Emp#, Skill-name, date-acquired]

Requires : [Project#, Skill-name]

Assigned : [Emp#, Project#, start-date, end-date]

Consulting Company Relational Model

Consulting Company Relational Model


EmployeeEmp# name address dob hourly-

rate741 Fred Smith 12 Peachtree Rd 1 Jan 1960 75852 Sarah Thomas 807 Piedmont Rd 6 May 1959 85963 Daniel McCarthy 4321 Cobb Dr 15 Oct 1961 69357 Ellen Lewis 15 Peachtree Rd 14 Feb 1961 55

ClientClient--Id name phone date-signed emp#1150 Joe Johnson 555-7412 14 Dec 1998 8521151 Stacey Smith 555-8523 7 Jan 1999 7411152 Donald Davis 888-3699 26 Jan 1999 8521153 Ed Edwards 777-9513 28 Feb 1999 963

ProjectProject# name date-began date-completed client-id9357 Virtual Courtyard 30 Jan 1999 11529159 Metro 8 Jan 1999 1 Mar 1999 11519752 Pontiac 5 Mar 1999 11539684 Looking Glass 30 Dec 1998 15 Feb 1999 1150

SkillSkill-name descriptionRelational database Relational db design and implementationObject-oriented database Object-oriented db design and implementationData Mining Implementing data mining systemsElectronic Commerce Intranet development and ecommerce

applications


Has-skillEmp# Skill-name date-required852 Electronic Commerce 7 Jan 1999852 Relational database 30 Dec 1998741 Relational database 15 Jan 1999852 Data Mining 10 Jan 1999963 Data Mining 15 Mar 1999

RequiresProject# Skill-name9357 Electronic Commerce9684 Relational database9159 Relational database9684 Data Mining9357 Data Mining9752 Data Mining

AssignedEmp# Project# start-date end-date852 9357 30 Jan 1999741 9159 8 Jan 1999 1 Mar 1999963 9752 5 Mar 1999852 9684 30 Dec 1998 15 Feb 1999


SQL QuerySQL Query

SELECT columns FROM tables WHEREconditions ORDER BY columns

•What date was the project called “Metro” completed? Select date-completed From project Where name=‘Metro’

•Answer: 1 Mar 1999


SQL QuerySQL Query

•What is the name of the client who sponsors the project called “Pontiac”? Select client.name From client, project Where project.name=‘Pontiac’ and project.client-id=client.client-id

•Answer: Ed Edwards


•What skills are required for the project called “Virtual Courtyard”?

SELECT requires.skill-name

FROM requires, project

WHERE project.name= ‘Virtual Courtyard’ and

requires.project# = project.project#

Answer: Electronic Commerce

Data Mining

SQL QuerySQL Query

Copyright Kathy S. Schwaig, 20011 MBA 8473 Kathy S. Schwaig Information Technology.

Documents

Transcript of Copyright Kathy S. Schwaig, 20011 MBA 8473 Kathy S. Schwaig Information Technology.