daniel adinugrohodatabase programming 1 database programming lecture on 04 – 05 – 2005

Daniel Adinugroho Database Programming1

DATABASE PROGRAMMING

Lecture on 04 – 05 – 2005


PREVIOUS LECTURE

1. Introduction to Database Design

- 6 Steps Database Design

2. Normalization.

- 1NF, 2NF and 3NF and example of normalization.

- BCNF, 4NF and 5NF


NEWS

1. All lecture materials are available on

http://192.168.1.1/teachers/adinugro/dp

2. Next Lecture will be QUIZ (06/05/2005)

- About Normalization

- OPEN BOOK

- DO NOT CHEAT!!!!!!!!!! or You will get 0.

- Exercise for exam, as the question is a typical exam questions,

- OK?


REVIEW OF NORMAL FORMS1NF -> eliminate repeating attributes

1. Identify repeating attributes.

2. All the key attributes are defined.

3. All attributes are dependent on the primary key.

2NF

1. It's in first normal form (1NF)

2. It includes no partial dependencies (where an attribute is

dependent on only a part of a primary key).

3NF

1. It's in second normal form (2NF)2. It contains no transitive dependencies (where a non-key attribute is dependent on

another non-key attribute


Project

numberProject name

Employee

numberEmployee name

Rate

category

Hourly

rate

1023 Madagascar travel site 11 Vincent Radebe A $60

12 Pauline James B $50

16 Charles Ramoraz C $40

1056 Online estate agency 11 Vincent Radebe A $60

17 Monique Williams B $50


1st NORMAL FORM

Project

numberProject name

Employee

numberEmployee name

Rate

category

Hourly

rate

1023 Madagascar travel site 11 Vincent Radebe A $60

1023 Madagascar travel site 12 Pauline James B $50

1023 Madagascar travel site 16 Charles Ramoraz C $40

1056 Online estate agency 11 Vincent Radebe A $60

1056 Online estate agency 17 Monique Williams B $50


2nd NORMAL FORM

Employee Table

Employee number Employee name Rate category Hourly rate

11 Vincent Radebe A $60

12 Pauline James B $50

16 Charles Ramoraz C $40

11 Vincent Radebe A $60

17 Monique Williams B $50


2nd NORMAL FORM

Project Table Employee

Project Table

Project

numberProject name

1023 Madagascar travel site

1056 Online estate agency

Project

number

Employee

number

1023 11

1023 12

1023 16

1056 11

1056 17


3rd NORMAL FORM

Employee Table Rate Table

Employee

numberEmployee name

Rate

category

11 Vincent Radebe A

12 Pauline James B

16 Charles Ramoraz C

11 Vincent Radebe A

17 Monique Williams B

Rate

category

Hourly

rate

A $60

B $50

C $40


3rd NORMAL FORM

Project Table Employee

Project Table

Project

numberProject name

1023 Madagascar travel site

1056 Online estate agency

Project

number

Employee

number

1023 11

1023 12

1023 16

1056 11

1056 17


DENORMALIZATION

Normalization is:

● Storing one fact in one place

● Storing related facts about single entity together

● every column of each entity refers non-transitively to only the unique identifier

for that entity.

Denormalization: is the reversal process of Normalization, which is a process to

store a fact in numerous places.


DENORMALIZATION(2)

Sometimes we need to do denormalization to accomplish quick retrieval capability

for data stored in relational database.

Of course we should (whenever possible) normalize our design to provide optimum

environment . However, in real world, denormalization is necessary.

Some issues need to be considered before denormalization:

● can the system achieve acceptable performance without denormalizating?

● will the performance of the system after denormalizating still unacceptable?

● will the system be less reliable due to denormalization?

If there is one 'yes' answer, we should avoid denormalization!


DENORMALIZATION (EXAMPLE)In order to justify denormalization we need to have a business reason for the alteration form 3rd NF. This example design is for a mail order company that has 120,000,000 customers to whom they must send catalogs. The top design is in 3rd normal form because the attributes for State, City, and Country are codependent on the PostalCode field. To fix that we created the PostalCode entity and related it back to the Customer records on the PostalCode foreign key in the Customer table.

However, during system testing it was discovered that the time required to produce 120,000,000 mailing labels through a two-table join was much longer than if the labels could be produced from a single table. The table was then denormalized by reintroducing the City, State, and Country attributes to the Customer table.

After doing this it would be heavily documented including the normal form that is violated, the reason for the violation, and the consequences of the violation. Any violation of a fully normalized design carries with it potential problems in the area of updates.


REFERENCES

● Craig, S. Mullin, Denormalization,

http://www.objectarchitects.de/ObjectArchitects/orpatterns/Performance/

Denormalization/CraigMullinsGuidelines/i001fe02.htm ● Ian Gilfillan, Database Normalization,

http://www.databasejournal.com/sqletc/article.php/1428511● Mike Hillyer, An Introduction to Database Normalization,

http://dev.mysql.com/tech-resources/articles/intro-to-normalization.html● David Faour, Database Normalization,

http://www.serverwatch.com/tutorials/article.php/1549781

daniel adinugrohodatabase programming 1 database programming lecture on 04 – 05 – 2005

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