04 data normalization 1

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DataNormalization (1)

1 Copyright © 2010 Jerry Post. All rights reserved.

IS240 – DBMS

Lecture # 4 – 2010-02-01M. E. Kabay, PhD, CISSP-ISSMP Assoc . Prof . Informat ion As surance

School of Bus iness & Management, Norwich University

mailto:[email protected] V: 802.479.7937

Topics

Why Normalization?

Definitions

Client B illing Example

First Normal Form

This material wacreated by

Prof Jerry Postand has been

reformatted by

Prof M. E. Kabay


econ orma o rm

Third Normal Form

Checking Your Work (Quality Control)

Why Normalization? Need standardized data definition

Advantages of DBMS requ ire carefu l design

Define data correctly and the rest is much easier

It especially makes it easier to expand databaselater

Method a lies to most models and most DBMS


Similar to Entity-Relationship

Similar to Objects (without inheritance and methods)

Goal: Define tables carefull y

Save space

Minimize redundancy Protect data

Definitions Relational database: A collection of tables.

Table: A collection of columns (attributes) describing an entity.Individual objects are stored as rows of data in the table.

Property (attribute): a characteristic or descriptor of a class or entity.

Every table has a primary key.

The smallest set of c olumns that uni quely identifies any row

Pr imar ke s can s an more than one column concatenated


keys)

We often create a primary key to ensure uniqueness (e.g.,CustomerID, Product#, . . .) called a surrogate key.

EmployeeID TaxpayerID LastName Firs tName HomePhone Address12512 888-22-5552 Car to m Abd ul (603) 323-9893 252 So ut h St reet15293 222-55 -3737 Venet iaan Roland (804) 888-6667 937 Paramar ibo Lane22343 293-87-4343 J oh ns on Jo hn (703) 222-9384 234 Mai n Str eet29387 837-36-2933 St en hei m Su san (410) 330-9837 8934 W. Map le

Employee

Properties

Rows/ObjectsClass: Employe

Primary key

Keys

Primary key

Every table (object) must have a primary key

Uniquely identifies a row (one-to-one)

Concatenated (or composite) key

Multiple columns needed for primary key


Identify repeating relationsh ips (1 : M or M : N)

Key columns are underlined

First step

Collect user documents

Identify possible keys

For each attribute_1 can there be manyattribute_2? If so, make attribute_2 a key

Notation

Table name

Primary key is underlined

Table columns

Customer(CustomerID, Phone, Name, Address, City, State, ZipCode


CustomerID Phone LastName FirstName Address City State Zipcode

1 502-666-7777 Johnson Martha 125 Main Street Alvaton KY 421222 502-888-6464 Smith Jack 873 Elm Street Bowling Green KY 421013 502-777-7575 Washington Elroy 95 Easy Street Smith’s Grove KY 421714 502-333-9494 Adams Samuel 746 Brown Drive Alvaton KY 421225 502-474-4746 Rabitz Victor 645 White Avenue Bowling Green KY 421026 616-373-4746 Steinmetz Susan 15 Speedway Drive Portland TN 371487 615-888-4474 Lasater Les 67 S. Ray Drive Portland TN 371488 615-452-1162 Jones Charlie 867 Lakeside Drive Castalian Springs TN 370319 502-222-4351 Chavez Juan 673 Industry Blvd. Caneyville KY 4272110 502-444-2512 Rojo Maria 88 Main Street Cave City KY 42127



Identifying Key Columns

Orders

OrderItems

OrderID Date Customer 8367 5-5-04 67948368 5-6-04 9263

Each order hasonly one customer.So Customer is notpart of the key.We can uniqu ely identify each

order simply by its OrderID.


OrderID Item Qu ant ity8367 229 28367 253 48367 876 18368 555 48368 229 1

Each order hasmany items.Each item can appear on many orders.So OrderID and Itemare both part of the key.We need both the OderID &

the Item to uniquely identify a

row in th e order.

Surrogate Keys

Real wor ld keys sometim es cause problems in a database.

Ass umpt ions about uniqueness are of ten w rong

E.g., using l astname_first name as a key does not work!

Example: Customer

Avo id phone n umb ers: peo ple may not not ify you w hen

numbers change.


Avo id SSN (pr ivacy and most bus inesses are no tauthorized to ask for verification, so you coul d end upwith duplicate values)

Often best to let the DBMS generate unique values

Acc ess: AutoNumb er

SQL Server: Identit y

Oracle: Sequences (but require additional programmi ng

Drawback: Numbers are not related to any busin ess data, sthe application needs to hide them and provide other look umechanisms.

Common Order System

Customer

Order

Salesperson

OrderItem

1*

1

*1

*


Item

1*

Customer(Cust omerID, Name, Address, Cit y, Phone)

Salesperson(EmployeeID, Name, Commis sion, DateHired)

Order(OrderID, OrderDate, CustomerID, Emplo yeeID)OrderItem(OrderID, ItemID, Quantit y)

Item(ItemID, Description, ListPrice)

Client Billing Example

Client Billing

Client(ClientID, Name, Address, BusinessType)

Partner(PartnerID, Name, Speciality, Office, Phone)

PartnerAssignment(PartnerID, ClientID, DateAcquired)

Billing(ClientID, PartnerID, Date/Time, Item, Description, Hours, AmountBilled


Each partner can be assigned many clients.

Each client can be assigned to many partn ers.

Table names

Client(ClientID, Name, Address, BusinessType)

Partner(PartnerID, Name, Specialit y, Office, Phone)

PartnerAssignment(PartnerID, ClientID, DateAcquired)

Client Billing: UnusualBusiness Rules

combine


Billing(ClientID, PartnerID, Date/Time, Item, Description, Hours, AmountBilled)

Suppose each client is assigned to exactly o nepartner .

Cannot key PartnerID.

Would combine Client and PartnerAssignmenttables, since they have the same key.

Client Billing: More LikelyAssumptions

Cl ien tIDPar tner ID Date/Time Item Descr ip tion Hours AmountB il led

115 963 8-4-04 10:03 967 Stress analysis 2 $500

295 967 8-5-04 11:15 754 New Design 3 $750115 963 8-8-04 09:30 967 Stress analysis 2.5 $650

Billing


.

Each Partner may work wit h many clients.

Each client may work with many partners.

Each partner and client may wo rk together manytimes.

The identifying f eature is the date/time of the service.

What happens if we do not i nclude Date/Time as a key?



Sample: Video DatabasePossible Keys


Initial Objects (Entities) Customers

Key: Assign aCustomerID

Sample Properties

Name

Address

RentalTransaction

Event/Relationship

Key: AssignTransactionID

Sample Properties

CustomerID


Videos

Key: Assign aVideoID

Sample Properties

Title

RentalPrice

Rating

Description

VideosRented

Event/Repeating list

Keys: TransactionID+ VideoID

Sample Properties

VideoCopy#

Initial Form Evaluation

Collect forms fromusers

Write down properties

Find repeating groups( . . .)

Lo ok for o tent ial k e s :

RentalForm(TransID, RentDate, CustomerID, Phone, Name, Address, City, State, ZipCode,(VideoID, Copy#, Title, Rent ) )


key

Identify computedvalues

Notation makes it easier to identify and solveproblems

Results equivalent todiagrams, but will fit onone or tw o pages

Problems with RepeatingSections

Storing data in this raw form wouldnot work very well. For example,repeating sections will causeproblems.

Note the duplication of data.

RentalForm(TransID, RentDate, CustomerID, Phone, Name, Address, City, State, ZipCode(VideoID, Copy#, Title, Rent ) )

Repeating Section


,yet checked out a movie—where dowe store that cust omer’s data?

TransID RentDate CustomerID LastName Phone Address VideoID Copy# Title Rent1 4/18/04 3 Washington 502-777-7575 95 Easy Street 1 2 2001: A Space Odyssey $1.501 4/18/04 3 Washington 502-777-7575 95 Easy Street 6 3 Clockwork Orange $1.502 4/30/04 7 Lasater 615-888-4474 67 S. Ray Drive 8 1 Hopscotch $1.502 4/30/04 7 Lasater 615-888-4474 67 S. Ray Drive 2 1 Apocalypse Now $2.002 4/30/04 7 Lasater 615-888-4474 67 S. Ray Drive 6 1 Clockwork Orange $1.503 4/18/04 8 Jones 615-452-1162 867 Lakeside Drive 9 1 Luggage Of The Gods $2.503 4/18/04 8 Jones 615-452-1162 867 Lakeside Drive 1 5 1 Fabulous Baker Boys $2.003 4/18/04 8 Jones 615-452-1162 867 Lakeside Drive 4 1 Boy And His Dog $2.504 4/18/04 3 Washington 502-777-7575 95 Easy Street 3 1 Blues Brothers $2.004 4/18/04 3 Washington 502-777-7575 95 Easy Street 8 1 Hopscotch $1.504 4/18/04 3 Washington 502-777-7575 95 Easy Street 13 1 Surf Nazis Must Die $2.504 4/18/04 3 Washington 502-777-7575 95 Easy Street 17 1 Witches of Eastwick $2.00

Causes duplication

Problems with RepeatingSections

NamePhone AddressCityState

ZipCode

VideoID Copy# Title Rent1. 6 1 Clockwork Orange 1.50

Store repeating data

Al locate space

How much?Can’t be short

Wasted space

Customer Rentals


2. 8 2 Hopscotch 1.503.4.5.

{Unused Space}

Not in First Normal Form

e.g., How m any videoswill be rented at onetime?

What happens if we try tostore more than weplanned?

A bet ter def in it ioneliminates this problem.

First Normal FormRentalForm(TransID, RentDate, CustomerID, Phone, Name, Address, City, State, ZipCode,

(VideoID, Copy#, Title, Rent ) )

RentalForm2(TransID, RentDate, CustomerID, Phone, Name, Address, City, State, ZipCode)

RentalLine(TransID, VideoID, Copy#, Title, Rent )

Remove repeating sections

S l it into two tab les


Bring key from m ain and repeating section

RentalLine(TransID, VideoID, Copy#, . . .)

Each transaction can h ave many videos (key VideoID)

Each video can be rented on many transactio ns (keyTransID)

For each TransID and VideoID, only one Copy# (no keyon Copy#)



Nested Repeating Sections

Table (Key1, . . . (Key2, . . . (Key3, . . .) ) )

Table1(Key1, . . .) TableA (Key1,Key2 . . .(Key3, . . .) )


Nested: Table (Key1, aaa. . . (Key2, bbb. . . (Key3,ccc. . .) ) )

First Normal Form (1NF)

Table1(Key1, aaa . . .)

Table2(Key1, Key2, bbb . .)

Table3(Key1, Key2, Key3, ccc. . .)

Table2 (Key1, Key2 . . .) Table3 (Key1, Key2, Key3, . . .)

First Normal Form Problems(Data)TransID RentDate C ustID Phone LastName FirstName Address City State ZipCode1 4/18/04 3 502-777-7575 Washington Elroy 95 Easy Street Smith's Grove KY 421712 4/30/04 7 615-888-4474 Lasater Les 67 S. Ray Drive Portland TN 371483 4/18/04 8 615-452-1162 Jones Charlie 867 Lakeside Drive Castalian Springs T N 370314 4/18/04 3 502-777-7575 Washington Elroy 95 Easy Street Smith's Grove KY 42171

1NF split s repeatinggroups

Stil l have rob lems


TransID VideoID Copy# Title1 1 2 2001: A Space Odyssey1 6 3 Clockwork Orange2 8 1 Hopscotch2 2 1 Apocalypse Now2 6 1 Clockwork Orange3 9 1 Luggage Of The Gods3 15 1 Fabulous Baker Boys3 4 1 Boy And His Dog4 3 1 Blues Brothers4 8 1 Hopscotch4 13 1 Surf Nazis Must Die4 17 1 Witches of Eastwick

Replication

Hiddendependency:

If a video has notbeen rented yet,then what is itstitle?

Second Normal FormDefinition

Each non-key column Dependence (definition )

RentalLine(TransID, VideoID, Copy#, Title, Rent)

Depend only on VideoID

Depends on both TransID and VideoID


entire key.

Appl ies only toconcatenated keys

Some columnsdepend on only partof the key

Split those into anew table.

If, given a value for the key,you always know the valueof the property in question,then that property is said todepend on the key.

If you change part of a keyand the questionable

property does not change,then the table is not in 2NF.

Second Normal FormExample

Title depends only on VideoID

RentalLine(TransID, VideoID, Copy#, Title, Rent)

VideosRented(TransID, VideoID, Copy#)

Videos(VideoID, Title, Re


Rent depends on VideoID

This statement is actually a business rule.

It might be different at different stores.

Some stores might charge a different rent fo r eachvideo depending on the day (or time).

Each non-key column depends on the whole key.

Second Normal FormExample (Data)

Tr an sID Vi deo ID Cop y#1 1 21 6 32 2 1

2 6 12 8 13 4 13 9 1


VideoID Title Rent1 2001: A Space Odyssey $1.502 Apocalypse Now $2.003 Blues Brothers $2.00

i

Videos(VideoID, Title, Rent)


3 15 14 3 14 8 14 13 14 17 1

4 Boy And His Dog $2.505 Brother From Another Planet $2.006 Clockwork Orange $1.507 Gods Must Be Crazy $2.008 Hopscotch $1.50

RentalForm2(TransID, RentDate, CustomerID, Phone,Name, Address, City, State, ZipCode)

(Unchanged)

Second Normal FormProblems (Data)

TransID RentDate C ustID Phone LastName FirstName Address City State ZipCode1 4/18/04 3 502-777-7575 Washington Elroy 95 Easy Street Smith's Grove KY 421712 4/30/04 7 615-888-4474 Lasater Les 67 S. Ray Drive Portland TN 37148

3 4/18/04 8 615-452-1162 Jones Charlie 867 Lakeside Drive Castalian Springs T N 370314 4/18/042 3 502-777-7575 Washington Elroy 95 Easy Street Smith's Grove KY 42171



Even in 2NF, problems remain

Replication

Hidden dependency

If a customer has not rented avideo yet, where do we store their personal data?

Solution: split table.



Third Normal FormDefinition

Each non-key column mus tde end on nothin but he

Dependence (definiti on)


Depend only on CustomerID

Depend on TransID


key.

Some columns depend oncolumns that are not partof the key.

Split those int o a newtable.

Example: Customer’sname does not change for every transaction.

, ,you always know the valueof the property in question,then that property is said todepend on the key.

If you change the key andthe questionable propertydoes not change, then thetable is not in 3NF.

Third Normal Form Example

Customer attributes depend only o n Customer ID


Rentals(TransID, RentDate, CustomerID )

Customers(CustomerID, Phone, Name, Address, City, State, ZipCode )


Split them into new table (Customer)

Remember to leave CustomerID in Rentals table.

We need to be able to r econnect tables.

3NF is sometimes easier to see if you identify primaryobjects at the start—then you wo uld recognize thatCustomer was a separate object.

Third Normal Form ExampleData

TransID RentDate CustomerID1 4/18/04 32 4/30/04 73 4/18/04 84 4/18/04 3


RentalForm2(TransID, RentDate, CustomerID, Phone, Name, Address, City, State, ZipCode


CustomerID Phone LastName FirstName Address City State ZipCode1 502-666-7777 Johnson Martha 125 Main Street Alvaton KY 421222 502-888-6464 Smith Jack 873 Elm Street Bowling Green KY 421013 502-777-7575 Washington Elroy 95 Easy Street Smith's Grove KY 421714 502-333-9494 Adams Samuel 746 Brown Drive Alvaton KY 421225 502-474-4746 Rabitz Victor 645 White Avenue Bowling Green KY 421026 615-373-4746 Steinmetz Susan 15 Speedway DrivePortland TN 371487 615-888-4474 Lasater Les 67 S. Ray Drive Portland TN 371488 615-452-1162 Jones Charlie 867 L akeside Drive Castalian Springs T N 370319 502-222-4351 Chavez Juan 673 Industry Blvd. Caneyville KY 4272110 502-444-2512 Rojo Maria 88 Main Street Cave City KY 42127




Third Normal Form Tables(3NF)

CustomerIDPhoneLastName

Customers

TransIDRentDateCustomerID

Rentals

TransIDVideoIDCopy#

VideosRented1

*

1

*

*






FirstName AddressCityStateZipCode

VideoIDTitleRent

Videos

1

3NF Rules/Procedure

Split out r epeating sections

Be sure to incl ude a key from the parent sectionin the new piece so the two parts can be

recombined. Verify that the keys are correct


key?

Are one-to-many and many-to-many relationshipscorrect?

Check “ many” for keyed columns and “one” for non-key columns.

Make sure that each non-key column depends onthe whole key and nothing but the key.

No hidden dependencies.

Checking Your Work (QualityControl) Look for one-to-many relationships.

Many side should be keyed (underlined).

e.g., VideosRented(Trans ID, VideoID, . . .).

Check each column and ask if i t should be 1 : 1 or 1: M.

If add a key, r enormalize.


Verify no repeating s ections (1NF)

Check 3NF

Check each colum n and ask:

Does it depend on the whole key and nothing butthe key?

Verify that the tables can be reconnected (joined) toform the original tables (draw lines).

Each table represents one object.

Enter sample data—look for r eplication.



HOMEWORK REQUIRED by Sun 14 Feb 2010 at 23:59

Study Chapter 3 thoroughly using SQ3R

Answer Review Questions for yourself

For 10 points each, solve and submit problems 1 & 3by creating diagrams in DBDesign for examination by

the professor


Sally’s Pet Store questions 8-11 (40 pts total)

OPTIONAL by Sun 14 Feb 2010 at 23:59

Rolling Thunder Bicycl es problems 12 and/or 13 (10pts each)

Corner Med problems 14 (incl optional) and/or 15 (10pts each)

DISCUSSION


04 data normalization 1

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