Boyce-Codd Normal Form (BCNF) is a higher level of database normalization that addresses certain anomalies that might still exist in databases normalized up to 3NF. To achieve BCNF, a database should already be in 3NF. BCNF ensures that for every non-trivial functional dependency X -> Y, X must be a superkey. Let’s continue using the Student Course Registration Database example and work towards achieving BCNF:
We have the following tables:
Step 1: Identify Violations of BCNF
BCNF focuses on ensuring that non-trivial functional dependencies have superkeys as their left-hand sides. In our current structure, we have a functional dependency
CourseID -> CourseName, Instructor in the
CourseDetails table. However,
CourseID is not a superkey; both
CourseName are needed to uniquely identify a course.
Step 2: Create a New Table
We need to create a new table with a candidate key that includes
CourseName, allowing us to remove the functional dependency violation.
Step 3: Update Original Table
Instructor columns from the
CourseDetails Table (BCNF):
Step 4: Update Dependencies
StudentRegistrations table to reference the new
StudentRegistrations Table (BCNF):
Conclusion: The database is now in Boyce-Codd Normal Form (BCNF). We have resolved the violation of BCNF by splitting the
CourseDetails table into
CourseInstructors tables. This ensures that every non-trivial functional dependency has a superkey as its left-hand side.
Keep in mind that achieving BCNF doesn’t necessarily mean your database is fully optimized for all use cases. Depending on your specific requirements and the complexity of your data, further normalization or denormalization might be necessary to strike the right balance between data integrity and performance.