Third Normal Form (3NF) | Database Normalization | DBMS

Summary

This video provides a comprehensive overview of the third normal form (3NF) in database normalization, building on concepts from the first and second normal forms. It highlights the importance of eliminating transitive dependencies, where non-key attributes depend on other non-key attributes. Through a practical example involving a school score table, the video illustrates how to identify and resolve these dependencies by creating a separate exam table. Viewers are encouraged to engage with the content and share their understanding of database normalization, ensuring a solid foundation in efficient data organization.

Takeaways

• 😀 The third normal form (3NF) is crucial in database normalization and requires a table to be in second normal form (2NF) without transitive dependencies.
• 😀 Viewers are encouraged to watch previous videos on the first and second normal forms for a comprehensive understanding of normalization.
• 😀 In the score table, the primary key is a composite key made of student ID and subject ID, which defines unique records.
• 😀 The score table was updated to include exam name and total marks, addressing additional necessary information.
• 😀 Transitive dependency occurs when an attribute depends on a non-prime attribute instead of the primary key.
• 😀 The exam name depends on both the student and the subject, demonstrating how dependencies can be complex.
• 😀 Total marks are dependent on exam name, showing the variability of marks based on the type of exam.
• 😀 Resolving transitive dependencies involves creating a separate exam table to store related attributes like exam name and total marks.
• 😀 Using an exam ID in the score table helps maintain normalization and organizes data more effectively.
• 😀 Understanding and applying 3NF improves data integrity and reduces redundancy in database design.

Q & A

What is the main topic of this video?

The main topic of the video is the third normal form (3NF) in database normalization.

What are the prerequisites for understanding the third normal form?

Viewers are encouraged to watch the videos on the first normal form (1NF) and second normal form (2NF) before diving into 3NF.

What tables are being discussed in the normalization process?

The tables discussed are the student, subject, and score tables in a school database.

What was the issue with the previous score table in the 2NF?

The score table needed additional fields for exam name and total marks, which were not included in the previous normalization.

What does it mean for a table to be in third normal form?

A table is in third normal form if it is in 2NF and has no transitive dependencies.

What is transitive dependency?

Transitive dependency occurs when a non-prime attribute depends on another non-prime attribute rather than directly on the primary key.

How is the primary key structured in the updated score table?

The primary key in the updated score table is a composite key made up of student ID and subject ID.

Why is total marks considered a transitive dependency in this context?

Total marks depends on exam name, which is not part of the primary key, creating a transitive dependency that must be resolved.

What solution is proposed for resolving the transitive dependency?

The proposed solution is to create a separate exam table that includes exam name and total marks, using an exam ID to reference it in the score table.

What is the final outcome for the score table after normalization to 3NF?

After normalization to 3NF, the score table effectively stores more information without transitive dependencies, allowing for better data organization.