Unnormalized form (UNF), sometimes also known as an unnormalized relation or non first normal form (NF2) relation, is a way of representing data in data model. It is the simplest form of representing tables in a database and does not conform to any of the forms of normalization. It is characterized by data redundancy and often contains complex data structures within a single attribute.
Contents
Overview
A relation in unnormalized form is used to represent the data entered by a user through a form. If the form contains atomic fields, then the model can be considered in 1NF form. However, if the form contains dependent attributes, they are stored as a data structure (typically another table) within that attribute. Data in unnormalized form would not be considered under relational data model as latter consists of atomic data. Some basic uses of unnormalized relation include dealing with form data in offices. One form would correspond to one record in the database.
History
In 1970, E.F. Codd proposed the relational data model which was widely accepted as the standard data model. At that time, office automation was the major use of data storage systems, which resulted in proposal of many NF2 data models like Schek model, Jaeschke models (Non-recursive and recursive algebra) and Nested Table Data (NTD) model. IBM organized the first international workshop exclusively on this topic in 1987 which was held in Darmstadt,Germany. Moreover, a lot of research has been done and journals have been published to address the shortcomings of relational model. Since the turn of the century, NoSQL databases have become more and more popular owing to the demands of Web 2.0.
Example
Students take courses:
The above table represents data in unnormalized form as there are multiple values of an attribute (course) for one tuple unlike the data in first normal form. Here, one student can take several courses and that data will be reflected in a single row in the database. Additionally, Chemistry is being stored two times in the database which results in a lot of memory consumption. Since atomicity is a prerequisite for a relational model this kind of table structure can never be represented with the same.
Advantages and disadvantages
Advantages of unnormalized form over normalized forms are -
Disadvantages of unnormalized form are -
Modern applications
Today companies like Google, Amazon and Facebook deal with loads of data and storing that data in an efficient manner is always a big task. They use NoSQL database which is based on the principles of unnormalized relational model to deal with storage issue. Some of the examples of NoSQL databases are MongoDB, Apache Cassandra and Redis. These databases are more scalable and easy to query with as they do not involve expensive operations like JOIN.