De-normalization in SQL

Question

Hi friends I want to know about de-normalization and when would we go for it ?

Satyapriya Nayak · Answer

http://en.wikipedia.org/wiki/Denormalization

Akkiraju Ivaturi · Answer

Facts are raw data that are stored in databases. There are two ways of storing data. One is one fact at one place and another one is one fact is scattered at different places. Storing at one place is normalization and to get all the related facts we need to join all the tables. But while doing modifications this type of database systems will be very useful. But if we need to join many tables the performance of the query while retrieving data gets degraded. Storing same fact at multiple places is denormalization and this type of architecture supports faster querying of the data. But at the time of modification the performance will be very poor. Most of the times denormalization principle is applicable where you need to query data more than with minor modifications. Like data warehousing and date mining where reporting of the data should be faster. Most of the business users and CEOs of the companies would like to analyze data based on the facts like salaries per year or number of employees joined per month in each year or any figures that helps in making decisions by the management.