When is Denormalization a Sound Approach to Improving Performance?
Denormalization sometimes implies the undoing of some of the steps of Normalization. Denormalization is not necessarily the reverse of the steps of Normalization. Denormalization does not imply complete removal of specific Normal Form levels. Denormalization results in duplication. It is quite possible that table structure is much too granular or possibly even incompatible with structure imposed by applications. Data warehouse databases usually require copying in order to achieve Denormalization of an interactive application OLTP or client server database. The result is two databases. The OLTP database is highly Normalized and the data warehouse database is a Denormalized version of the OLTP database. Denormalization usually involves merging of multiple transactional tables or multiple static tables into single transactional or static tables respectively. Denormalization does not generally involve merging of transactional and static data tables. This implies that all Normal Forms but 2
