Microsoft® SQL Server 2012 Unleashed

Drawbacks of Normalization

One result of normalization is that data is stored in multiple tables. To retrieve or modify information, you usually have to establish joins across multiple tables. Joins are expensive from an I/O standpoint. Multitable joins can have an adverse impact on the performance of the system. The following sections discuss some of the denormalization techniques you can use to improve the performance of a system.

Tip

An adage for normalization is, “Normalize ‘til it hurts; denormalize ‘til it works.” To put this maxim into use, try to put your database in third normal form initially. Then, when you’re ready to implement the physical structure, drop back from third normal form, where excessive table joins are hurting performance. ...