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What is Normalization in DBMS?

Last Updated : 16 Apr, 2024
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The normalization concept for relational databases, developed by E.F. Codd, the inventor of the relational database model, is from the 1970s. Before Codd, the most common method of storing data was in large, cryptic, and unstructured files, generating plenty of redundancy and lack of consistency. When databases began to emerge, people noticed that stuffing data into them caused many duplications and anomalies to emerge, like insert, delete, and update anomalies. These anomalies could produce incorrect data reporting, which is harmful to any business. Normalization is a methodological method used in the design of databases to create a neat, structured, and structured table in which each table relates to just one subject or one-to-one correspondence.

The objective is to extensively reduce data redundancy and dependency. In essence, normalization was introduced and has continually been improved to rectify these specific aspects of data management. By organizing data in such a rigorous and stringent manner, normalization facilitates a significantly enhanced level of data integrity and enables more efficient data operations.

Understanding Normalization

DBMS normalization is referred to as a process to streamline database data correctly. This is because the redundancy, malfunctions, and integrity of the data are exceeded. In other words, normalization rearranges the database by splitting the tables to actually find the practical effects of the data management mixing up tables, any data will be lost.

Primary Terminologies

  • Database Management System (DBMS): A DBMS is the single most important feature that allows a person to create, read, update and delete data from their database, providing them with much-needed access to the data they may need. As a centralized system, it boosts data sharing and access, making normalization core to managing structured data.
  • Normalization: Normalization in DBMS Normalization is an essential part of your database in DBMS. It is the first intelligent design of the schema that organizes data systematically. In this case, data is essentially your foundation to an efficient, reliable, scalable and flexible database. What normalization basically does is ensure that your data is free of data redundancy or duplicate data and does not have data anomalies that would otherwise compromise its integrity.
  • Tables (relations) and Attributes: A table, also known as a relation in DBMS, is an organized structure of rows and columns . A row represents a unique record while a column display an attribute. Attributes provide meaningful context to our data; they are essential characteristics or properties of the entities stored in our tables. Channeling these entities, the storage of the relational data may deem more efficient as it becomes easy to query relationships between these entities.
  • Functional Dependencies:Functional dependencies are the most critical part of the relational database model. They are used for enforcing data integrity constraints and essential for database normalization. They provide logical and meaningful semantics between different attributes of a relation.
  • Data Redundancy: This is a term that should be kept in check when using a DBMS. Redundant data is data that is repeating itself in a database. When data is redundant, storage space is misappropriated and the database becomes more complex to use. Redundant data contributes to numerous errors and inaccuracies in a database. It’s one of the drivers of a normal – free database.
  • Data Anomalies: these are errors that are likely to occur during database transactions. Mismanagement of data can cause errors of different types such as insertion, ambiguity, and deletion. Normalized database systems cause the occur of errors in the sense that accuracies are now properly done.
  • Primary Key: A Primary Key is a column predefined to serve as a unique identifier of a database table . Essentially, a primary key makes each record unique, allowing it to be addressed and manipulated independently. A primary key is a key component of a database structure because it is essential for maintaining data integrity and streamlining the operation of a database.
  • Foreign Key: A foreign key is yet another essential database concept that links data tables and effectively solidifies the relational aspect of relational databases. In other words, a foreign key connects related entities and assures the integrity of database relationships. Overall, foreign keys contribute to the overall structure and coherence of a database by preventing redundant data. Hence, they make it easier to work with data and more meaningful.
  • Normal Forms: Normal forms are a set of systematic rules for deciding what tables to build and when to create them. The standard normal forms that include 1NF, 2NF, 3NF, BCNF, 4NF, and 5NF are a sequence or list of progressive rules or standards made to remove redundancy and preserve database integrity. ‘NF’ deplores each of the aforementioned abbreviations indicates a more stringent normalization level. Normalization helps to keep relationships and layout consistency and efficiency of data information that goes into your database.

Types of Normalization

Normalization usually occurs in phases where every phase is assigned its equivalent ‘Normal form’. As we progress upwards the phases, the data gets more orderly and hence less permissible to redundancy, and more consistent. The commonly used normal forms include:

  • First Normal Form (1NF): In the 1NF stage, each column in a table is unique, with no repetition of groups of data. Here, each entry (or tuple) has a unique identifier known as a primary key.
  • Second Normal Form (2NF): Building upon 1NF, at this stage, all non-key attributes are fully functionally dependent on the primary key. In other words, the non-key columns in the table should rely entirely on each candidate key.
  • Third Normal Form (3NF): This stage takes care of transitive functional dependencies. In the 3NF stage, every non-principal column should be non-transitively dependent on each key within the table.
  • Boyce-Codd Normal Form (BCNF): BCNF is the next level of 3NF that guarantees the validity of data dependencies. The dependencies of any attributes on non-key attributes are removed under the third level of normalization . For that reason, it ensures that each determinant be a candidate key and no dependent can fail to possess an independent attribute as its candidate key.
  • Fourth Normal Form (4NF): 4NF follows that data redundancy is reduced to another level with the treatment of multi-valued facts. Simply put, the table is in normal form when it does not result in any update anomalies and when a table consists of multiple attributes, each is independent. In other words, it collapses the dependencies into single vs. multi-valued and eliminates the root of any data redundancy concerned with the multi-valued one.

Why is Normalization Important?

Normalization is crucial as it helps eliminate redundant data and inconsistencies, ensuring more accurate, lean, and efficient databases. It also simplifies data management and enhances the speed and performance of the overall database system, thereby proving to be advantageous.


Let us assume the library database that maintains the required details of books and borrowers. In an unnormalized database, the library records in one table the book details and the member who borrowed it, as well as the member’s detail. This would result in repetitive information every time a member borrows a book.

Normalization splits the data into different tables — ‘Books’, “Members” and “Borrowed” and connects “Books” and “Members” with “Borrowed” through a biunique key. This removes redundancy, which means data is well managed, and there is less space utilization.


The concepts of normalization, and the ability to put this theory into practice, are key to building and maintaining comprehensive databases which are both strong and impervious to data anomalies and redundancy. Properly applied and employed at the right times, normalization boosts database quality, making it structured, small, and easily manageable.

Frequently Asked Questions on Normalization in DBMS – FAQs

What is the main purpose of normalization in DBMS?

DBMS normalization is primarily beneficial to achieve three functions. Firstly, it removes any form of duplicate data, which is essential to reduce storage and maintain overall data consistency. Secondly, it allows data dependences to stay normalized by design structurally placing data in tables . Finally, this step eliminates any form of data anomalies such as insert, updates and delete data anomalies.

What are the different levels of normalization?

Normalized takes several levels or forms, each with a particular rule set. The basic forms are referred to as the First Normal Form or 1NF, Second Normal Form or 2NF, and Third Normal Form or 3NF. The form which is even more stringent are the Boyce-Codd Normal Form or BCNF, Fourth Normal Form or 4NF, and Fifth Normal Form or 5NF. Each succeeding form implies higher bar compliance with normalization standards, starting from removing duplicate records with 1NF to addressing more sophisticated data dependencies with the subsequent forms.

Is it always necessary to normalize a database?

Normalization is not always needed. For example, primarily for performance reasons, if one’s database needs to perform complicated queries on large statistics. A concerning the method is that denormalization can be beneficial. Data can be retrieved with minimal queries by a denormalized database due to their redundancy, reducing execution time.

Can I reduce data redundancy through normalization in DBMS?

Definitely. Normalization in DBMS is already a proven process that reduces data redundancy to an extent. The more you separate data into brief and logical tables and identify relationships between those tables, the less repetitive data will be in your DBMS. As a result, making your database schema clearer, more predictable, and more consistent will enable your database structure to function correctly.

Is normalization always in DBMS beneficial in managing databases?

Yes, normalization minimizes repeated information and damage, although data structures will rapidly become complicated only once the DBMS is consolidated. In some cases, DBAs will intentionally leave some reduplication to ensure DBMS runs faster. Thus, it entirely depends on the contextual specifics for your database structure to normalize

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