Unnormalized form, also known as an unnormalized relation or non first normal form, is a simple databasedata model lacking the efficiency of database normalization. An unnormalized data model will suffer the pitfalls of data redundancy, where multiple values and/or complex data structures may be stored within a single field or attribute, or where fields may be replicated within a single table.
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 within that attribute. Data in unnormalized form would not be considered to be relational since it lacks atomic data. Some basic uses of unnormalized relations include dealing with form data in offices. One form would correspond to one record in the database.
The above tables represent data in unnormalized form as more than one value is stored in a single attribute within a row/tuple. This lack of defined atomicity means that the table has not reached the level of First normal form. Here, one student can take several courses and that data will be reflected in a single row in the database. One can see that relating entities based on 'course' is more problematic, as is ensuring consistency of data. Of somewhat less importance in modern systems, the word 'Chemistry' is being stored three times in the database which results in potentially excess memory consumption.
Advantages and disadvantages
Advantages of unnormalized form over normalized forms are -
It can deal with complex data structures like Objects, rows in a field.
Since there is no relation, querying this data model is simpler.
Restructuring data is easier.
Disadvantages of unnormalized form are -
Absence of relations means that data is often redundant.
CRUD operations are plagued by anomalies, and if they are not handled correctly, can result in data inconsistency.
Today, companies like Google, Amazon and Facebook deal with large amounts of data that are difficult to store efficiently. They use NoSQL databases, which are based on the principles of the unnormalized relational model, to deal with the storage issue. Some examples of NoSQL databases are MongoDB, Apache Cassandra and Redis. These databases are more scalable and easier to query with as they do not involve expensive operations like JOIN.
