1. Boyce-Codd Normal Form Kelvin Nishikawa SE157a-03 Fall 2006 Kelvin Nishikawa SE157a-03 Fall 2006

2. Overview 1NF, 2NF, and 3NF BCNF Conclusion 1NF, 2NF, and 3NF BCNF Conclusion

3. Database Normalization Each datum in the database should represented once. Purpose is to eliminate update, insert, and deletion anomalies. Normal Forms are increasingly strict subset of 1NF. Each datum in the database should represented once. Purpose is to eliminate update, insert, and deletion anomalies. Normal Forms are increasingly strict subset of 1NF.

4. First Normal Form Eliminate Repeating Groups Require uniquely identified rows

5. First Normal form 1 girl per row 2 Pamelas are uniquely identifiable.

6. Second Normal Form Eliminate Redundant Data

7. Second Normal Form Non-key columns are dependent on all columns of the primary key.

8. 2NF/3NF A Relation without non-key attributes is 2NF and 3NF.

9. Third Normal Form Eliminate Columns Not Dependent On Key i.e. if a column is in a relation, then it must be dependent on the key.

10. Third Normal Form Move non-key-dependent attributes to a new table.

11. Boyce-Codd Normal Form (BCNF) 3NF, but… All functional dependencies imply the only whole key. "The key, the whole key, and nothing but the key, so help me Codd." 3NF, but… All functional dependencies imply the only whole key. "The key, the whole key, and nothing but the key, so help me Codd."

12. Identifying (non)BCNF A Relation can be 3NF and not BCNF if: There are multiple candidate keys The keys are composed of multiple attributes There are common attributes between the keys. A Relation can be 3NF and not BCNF if: There are multiple candidate keys The keys are composed of multiple attributes There are common attributes between the keys.

13. Example of 3NF and BCNF Given: R(A,B,C,D,E) AB –> C AB –> D AB –> E DE –> C DE –> A DE –> B With the key AB Given: R(A,B,C,D,E) AB –> C AB –> D AB –> E DE –> C DE –> A DE –> B With the key AB Holds true for 3NF All left hands of functional dependencies are candidate keys. Breaks for BCNF There exist dependencies between candidate keys.

14. Summary BCNF if: No dependencies between candidate keys. 3NF BCNF if: No dependencies between candidate keys. 3NF No attributes dependent on non- keys. 2NF Attributes dependent on all parts of the key 1NF No repeating groups Each row uniquely identifiable.

15. Questions?