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Design MethodologyA structured approach that uses procedures, techniques, tools, and

documentation aids to support and facilitate the process of design.

Three main phases 1. Conceptual database design Understanding client data E-R (EER) Model Agreement between clients and designers E-R Model could be used for any database system

2. Logical database design Mapping E-R Model to (relational) database schema Normalization

3. Physical database design

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Mapping E-R Model to Relational Database Schema

1. Entity type Table schema

Composite Attributes

Multi-Value Attributes

2. How to maintain relationships?

Primary Key and Foreign Key

Many-to-Many

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How to maintain relationships?

Foreign Key

Primary key of another relation (table)Representing relationship between two

relations (tables)

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Foreign Key: Examples

Branch (Bno, Street, City, State, Zipcode, Phone) Staff (Sno, firstName, lastName, Address, Bno )

Owner (Ono, firstName, lastName, Phone (Multi-Value))PropertyForRent (Pno, Street, City, State, Zipcode, Ono)

Client (Cno, firstName, lastName, Phone, MaxRent, PrefType)Viewing (Cno, Pno, ViewDate, Comment)

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How to Describe a Table Schema? Database Design Language (DBDL)

Branch (Bno, Street, City, State, Zipcode, Phone) PK: Bno AK: Street, City, Zipcode Phone FK: None

Viewing (Rno, Pno, ViewDate, Comment) PK: Rno, ViewDate AK: None FK: Rno references Client (Cno) Pno references Property

Multiple AK/FK on different lines!

Viewing (Rno, Pno, ViewDate, Comment) PK: Rno, ViewDate AK: None FK: Rno, Pno

FK: Rno references Client (Cno) Pno references Property

One FK! Not two!References!

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Mapping Strong Entities to Relation (Table) Schemas

• Replacing composite attributes with simple attributes

• Adding new tables to remove multi-value attributes

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Replacing Composite Attributes with Simple Attributes

Name: Composite (FirstName, LastName)

Use two atriibutes:

FirstName

LastName

Address : Compsite (Street, City, State, Zipcode)

Use four attributes:

Street

City

State

Zipcode

Performance issue

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Composite Attributes

staffNo Name Address . . .

SL21 John White 1 main street, Platteville, WI 53818

SG37 Ann Beech 15 University Dr, Madison, WI 53706

SA9 Mary Howe 908 Western avenue, Dubuque, IA 52001-1234

Search on state or zip code

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Simple Attributes

staffNo firstName lastName Street City State zip

SL21 John White 1 main street Platteville WI 53818

SG37 Ann Beech 15 University Dr Madison WI 53706

SA9 Mary Howe 908 Western avenue

Dubuque IA 52001-1234

Search on state or zip code

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Removing Multi-Value Attributes

No multi-value attributes in relational databases

First Order Logic

No sets as set elements

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Multi-Value Attributes

branchNo street city state zipCode telNo

B001 1 main street

Platteville WI 53818 608-348-1234

608-348-3345

B002 15 university drive

Madison WI 53706 608-255-3034

608-255-1023

877-323-5678

… … … … … …

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Removing Multi-Value Attributes without Losing Data

Entity Type in E-R ModelBranch branchNo . . . telNo: multi-value

How to Store telNo? phoneOne phoneTwo

(When we know the limit of phone numbers at a branch: at most two)

Staff staffNo homePhone workPhone cellPhone . . .

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Each Branch Has at Most Three Phone Numbers

branchNo street . . . phone1 phone2 phone3

B001 1 main street

608-348-1234 608-348-3345

B002 15 university drive

608-255-3034 608-255-1023 877-323-5678

… … … … …

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Home Phone, WorkPhone and Cell Phone

staffNo street . . . homePhone workPhone cellPhone

SL21 1 main street

608-348-1234 608-348-3345

SG37 15 university drive

608-255-3034 608-255-1023 877-323-5678

SA79 … … 608-255-3847

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Multi-Value Attributes Without Limit

Entity Type in E-R ModelBranch branchNo . . . telNo: multi-value (NO LIMIT!)

More Examples

Student MajorWork Experience

Research publications . . .

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Replacing Multi-Value Attributes

branchNo . . . telNo

B001 608-348-1234

608-348-3345

B002 608-255-3034

608-255-1023

877-323-5678

… … …

branchNo Street City State zipCode

B001

B002

…

branchNo telNo

B001 608-348-1234

B001 608-348-3345

B002 608-255-3034

B002 608-255-1023

B002 877-323-5678

… …One table two tablesMulti-Value attribute multiple recordsPrimary Key Foreign Key

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Replacing Multi-Value Attributes

Entity Type in E-R ModelBranch branchNo . . . telNo: multi-value (NO LIMIT!)

How to Store telNo?Remove it from Branch and create a new table!

BranchPhone branchNo telPhone

What is the PK?Assumption: two branches don’t share the same phone #

Does it have a FK?

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Mapping Entity Type to Table Schema

Entity Type in E-R ModelBranch branchNo address: composite (street, city, state, zipCode) telNo: multi-value (with or without limit!)

Table Schema (DBDL)

Branch (branchNo, street, city, state, zip) PK: branchNo AK: street, city, zip FK: NONE

BranchPhone (branchNo, telPhone) PK: telPhone AK: NONE FK: branchNo references Branch

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Entity Type in E-R ModelStaff staffNo . . . DOB workExperince: multi-value Composite (start, end, org, position)

Store workExperince with staffNo in a new Table!WorkExperience staffNo start end org position

PK?Could create a new PK attribute (workExpID)

FK?

Mapping Entity Type to Table Schema

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Storing Work ExperienceEntity Type in E-R Model

Staff staffNo . . . DOB workExperince: multi-value Composite (start, end, org, position)

Table Schema (DBDL)Staff (staffNo, . . ., DOB) PK: staffNo AK: NONE FK: NONE

WorkExperience(workExpID, staffNo, start, end, org, position) PK: workExpID AK: ? FK: staffNo references Staff

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Design MethodologyA structured approach that uses procedures, techniques, tools, and

documentation aids to support and facilitate the process of design.

Three main phases 1. Conceptual database design Understanding client data E-R (EER) Model Contract between clients and designers E-R Model could be used for any database system

2. Logical database design Mapping E-R Model to (relational) database schema Normalization

3. Physical database design

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Mapping E-R Model to Relational database schema (DBDL)

Branch (Bno, Street, City, State, Zipcode) PK: Bno AK: Street, City, Zipcode Phone FK: None

BranchPhone (branchNo, telPhone) PK: branchNo, telPhone AK: NONE FK: branchNo references Branch

Staff (Sno, firstName, lastName, Address, Bno ) PK: Sno AK: None FK: Bno references Branch

WorkExperience(staffNo, start, end, org, position) PK: staffNo, start, org AK: NONE FK: staffNo references Staff

No multi-value attributes, no composite attributes.

Assignment 4

Due Wednesday, Feb 20

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