Normalization – Quick Glance

Normalization

1NF –
* Eliminate duplicative columns from the same table. ( Manager, Sub1, sub2, sub3 => Manager id, Sub id )
* Create separate tables for each group of related data and identify each row with a unique column or set of columns (the primary key).

adv : Scalability, efficient CURD

2NF –
* Remove subsets of data that apply to multiple rows of a table and place them in separate tables. ( a.k.a Eliminate duplication of data in rows, city/state/zip/ can go to a seperate table)
* Create relationships between these new tables and their predecessors through the use of foreign keys.

adv : Space savings, better readability

3NF –
* Remove columns that are not fully dependent upon the primary key.(a.k.a Don’t save data that can be computed on the fly from other fields in the table )

adv : Space savings, better readability

BCNF-
* A relation is in Boyce-Codd Normal Form (BCNF) if every determinant is a candidate key. (See the links in the box at right for definitions of determinant and candidate key.)

De-Normalization

Quick Check

  1. What are some benefits of denormalization?
  2. What problems can you encounter when you decide to introduce some denormal-ization into your model?

Quick Check Answers

  1. Some benefits of denormalization are improved performance, the need for fewer joins, and the ability to maintain history information.
  2. When you denormalize a database, you can encounter problems with data consistency, especially with aggregated data, which must be updated for any single event.

Reference :

http://technet.microsoft.com/en-us/library/cc505841.aspx

http://databases.about.com/od/specificproducts/a/normalization.htm

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