Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
?
Solved

Newbie Q. : Which Normalization Form?

Posted on 1998-12-10
2
Medium Priority
?
1,775 Views
Last Modified: 2011-10-03
Some books recommend the database design is to move the
Non-Normal Form to Boyce Codd Normal Form :
Non-NF -> 1NF -> 2NF -> 3NF ->BCNF

Does nobody use Non-NF now?
When should I use 1NF,2NF,3NF or BCNF?
What is the advantage/disadvantage to use each normalized form?
Is BCNF ALWAYS better than 3NF and 2NF?
Is 3NF ALWAYS better than 2NF?

Many thanks.
rgds.
alan
alanpong@hkstar.com
0
Comment
Question by:alanpong
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 4

Accepted Solution

by:
pagladasu earned 510 total points
ID: 1026083
The basic purpose of normalisation is to reduce redundancy in data and avoid problems in updates, inserts and deletes.
The 1st normal form is always required as a minimum in a relational model - by definition every relation will always be in 1NF.
The 2NF is needed only when you want to remove partial dependencies - ie, you have a composite primary key on which some of the non-key attributes are partially dependent.
The 3NF form is needed to remove transitive dependencies - requred when a non-key attribute is functionally dependent on another non-key attribute.
BCNF is a special type of 3NF and is needed to be addressed when the relation may be in 3NF and yet have 2 composite candiate keys with an overlapping attribute.
It is not always necessary for a relation to be in a higher normal form. A higher normal form does not always imply better performance. For example if your system has low update activities but has to generate a lot of queries from many relations,  then it is better to keep them in lower normal forms as this would reduce the overheads of doing joins.

Thanks
pagladasu
0
 
LVL 1

Author Comment

by:alanpong
ID: 1026084
After seeking more examples in some reference books, I
understand now.

0

Featured Post

Ask an Anonymous Question!

Don't feel intimidated by what you don't know. Ask your question anonymously. It's easy! Learn more and upgrade.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article shows the steps required to install WordPress on Azure. Web Apps, Mobile Apps, API Apps, or Functions, in Azure all these run in an App Service plan. WordPress is no exception and requires an App Service Plan and Database to install
Your data is at risk. Probably more today that at any other time in history. There are simply more people with more access to the Web with bad intentions.
This is a high-level webinar that covers the history of enterprise open source database use. It addresses both the advantages companies see in using open source database technologies, as well as the fears and reservations they might have. In this…
This lesson discusses how to use a Mainform + Subforms in Microsoft Access to find and enter data for payments on orders. The sample data comes from a custom shop that builds and sells movable storage structures that are delivered to your property. …
Suggested Courses

609 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question