If you’ve been working with databases for a while, chances are you’ve heard the term normalization. Maybe someone has asked you, “Is that database normalized?” or “Is that in BCNF?” Normalization is often seen as a luxury that only academics have time for. However, understanding the principles of normalization and applying them to your day-to-day database design tasks isn’t that difficult, and it can dramatically improve the performance of your DBMS.

In this article we introduce the concept of normalization and briefly discuss the most common normal forms.

Normalization is the process of efficiently organizing data in a database. The normalization process has two goals: eliminating redundant data (for example, storing the same data in more than one table) and ensuring that data dependencies are logical (storing only related data in a table). Both are valuable goals, because they reduce the amount of space a database consumes and ensure that data is stored logically.

The database community has developed a set of guidelines to ensure that databases are normalized. These are called normal forms and are numbered from one (the lowest form of normalization, first normal form or 1NF) through five (fifth normal form or 5NF). In practical applications, you often see 1NF, 2NF, and 3NF, along with the occasional 4NF. Fifth normal form is very rarely seen and is not discussed in this article.