10 Differences Between 3nf and bcnf

The Difference Between 3NF and BCNF in Database Normalization

Database normalization is an essential concept in the field of relational databases, aiming to eliminate data redundancy and improve data integrity. Two widely used normal forms are the Third Normal Form (3NF) and Boyce-Codd Normal Form (BCNF). In this article, we will explore what 3NF and BCNF are, their uses, and highlight the key differences between them.

What is/are 3NF?

The Third Normal Form (3NF) is a database normalization technique that ensures tables contain no transitive dependencies. In simpler terms, it eliminates redundant data in a relational database schema. To adhere to 3NF, a table must first satisfy the conditions of both First Normal Form (1NF) and Second Normal Form (2NF).

Examples of 3NF:

Consider a database for an online store. In a 3NF-compliant schema, the “Customer” table would not contain duplicated customer addresses. Instead, the address would be stored in a separate “Address” table and linked to the respective customer through a foreign key.

Uses of 3NF:

Applying 3NF brings several benefits, such as:

  • Reducing data redundancy and improving storage efficiency.
  • Minimizing anomalies when updating or deleting data.
  • Streamlining database maintenance and modifications.

What is/are BCNF?

Boyce-Codd Normal Form (BCNF) is an advanced normal form that ensures every determinant in a table is a candidate key. In BCNF, a determinant is any attribute that uniquely determines other attributes in the table. It is also an extension of 3NF, providing a higher level of normalization.

Examples of BCNF:

Let’s consider a database for a university. In a BCNF-compliant schema, the “Course” table would have all its non-key attributes depending solely on the primary key, such as the course code. Any independent attributes, such as the instructor’s name, would be stored in a separate “Instructor” table.

Uses of BCNF:

BCNF helps to improve data integrity and avoid anomalies even further than 3NF. It offers benefits such as:

  • Eliminating additional redundancy and dependencies.
  • Ensuring no logical inconsistencies arise during data manipulation.
  • Facilitating optimal database design.

Differences between 3NF and BCNF:

Difference Area 3NF BCNF
Dependency on Candidate Keys Allows dependencies on non-prime attributes, including transitive dependencies. Does not allow any dependency on non-prime attributes.
Normal Form Hierarchy It is a lower level of normalization, building upon First and Second Normal Forms. It is a higher level of normalization, extending beyond Third Normal Form.
Number of Candidate Keys Has one or more candidate keys. Has only one candidate key.
Data Redundancy May still have some data redundancy remaining after normalization. Eliminates all possible data redundancy.
Updating Anomalies Can exhibit certain anomalies during data updates. Avoids all possible anomalies during data updates.
Data Integrity Ensures a good level of data integrity. Offers a higher level of data integrity than 3NF.
Data Modification Flexibility Allows more flexibility for modifications due to less strict constraints. Imposes stricter constraints on data modifications.
Level of Decomposition Decomposes the table to eliminate transitive dependencies. Further decomposes the table to remove all dependencies on non-key attributes.
Practical Implementation Often more practical for everyday database designs. Usually implemented in complex database systems with specific needs.
Normalization Effort Easier to achieve compared to BCNF. May require additional normalization effort beyond 3NF.


In summary, both 3NF and BCNF are important normal forms in database normalization. While 3NF eliminates transitive dependencies and reduces redundancy, BCNF takes normalization a step further by ensuring that every determinant is a candidate key. BCNF provides a higher level of integrity and eliminates all possible anomalies, making it suitable for more complex database systems. The choice between 3NF and BCNF depends on the specific requirements and complexity of the database design.

People Also Ask:

Q: Are 3NF and BCNF the only normal forms?

A: No, there are several other normal forms, such as First Normal Form (1NF), Second Normal Form (2NF), Fourth Normal Form (4NF), and Fifth Normal Form (5NF). Each normal form defines a set of rules to eliminate different types of data redundancies and anomalies.

Q: Can a table be in both 3NF and BCNF?

A: Yes, a table can be in both 3NF and BCNF if it satisfies the conditions of both normal forms simultaneously. However, it is more common for a table to be in one normal form but not the other, depending on the specific design and dependencies.

Q: Which normal form is the best?

A: There is no definitive answer as to which normal form is the best. The choice of normal form depends on the specific requirements, complexity, and trade-offs of the database design. Higher normal forms provide more strict rules and better data integrity but may also require more effort during normalization.

Q: Can we skip normalization and directly use BCNF?

A: It is generally not recommended to skip normalization steps and directly use BCNF in database design. It is important to follow a progressive normalization process to ensure data integrity and efficient database operations. Starting from lower normal forms and gradually moving towards higher forms helps create a well-structured and optimized database schema.

Q: Does database normalization impact performance?

A: While normalization improves data integrity and reduces redundancy, it can introduce certain performance considerations. Highly normalized schemas may require additional joins for retrieving data, which can impact query performance. Striking the right balance between normalization and performance is essential, considering factors such as the volume of data, query patterns, and system requirements.

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