What is De-normalization ? Why should we go for De-normalization ?

De-normalization is the process of attempting to optimize the performance of a database by adding redundant data. It is a technique to move from higher to lower normal forms of database modeling in order to improve the data retrieval performance.

In a normalized database, more joins are required to gather all the information from multiple tables, as data is stored in multiple tables rather than in one large table. Queries that have a lot of complex joins will require more CPU usage and will adversely affect performance. So in order to improve the query performance we go for  De-normalization process.