1. Al-Imam University Girls Education Center Collage of Computer Science 1 nd Semester, 1432/1433H Chapter 10_part2 Functional Dependencies and Normalization for Relational Databases

2. Introduction to Databases 2 Outline Normal Forms Based on Primary Keys  First Normal Form  Second Normal Form  Third Normal Form

3. Introduction to Databases 3 Introduction to Normalization Normalization: Process of decomposing unsatisfactory "bad" relations by breaking up their attributes into smaller relations Normal form: Condition using keys and FDs of a relation to certify whether a relation schema is in a particular normal form  2NF, 3NF, BCNF based on keys and FDs of a relation schema

4. Introduction to Databases 4 First Normal Form Disallows composite attributes, multivalued attributes, and nested relations; attributes whose values for an individual tuple are non-atomic. Considered to be part of the definition of relation

5. Introduction to Databases 5 Normalization into 1NF

6. Introduction to Databases 6 Examples First Normal Form EMP_PROJ (Ssn, Ename, {Phone#}) { } Mulitvalue attribute EMP_PROJ1 (Ssn, Ename) EMP_PROJ2 (Ssn, Phone#) ■EMP_PROJ (Ssn, Ename (Fname, Lname)) ( ) composite attribute EMP_PROJ (Ssn, Fname,Lname) ■EMP_PROJ (Ssn, Ename, {PROJS (Pnamber, Hours)}) EMP_PROJ1 (Ssn, Ename) EMP_PROJ2 (Ssn, Pnamber, Hours)

7. Introduction to Databases 7

8. 8 Second Normal Form Uses the concepts of FDs, primary key Definitions:  Prime attribute - attribute that is member of the primary key K  Full functional dependency - a FD Y  Z where removal of any attribute from Y means the FD does not hold any more

9. Introduction to Databases 9 Examples Second Normal Form {SSN, PNUMBER}  HOURS is a full FD since neither SSN  HOURS nor PNUMBER  HOURS hold {SSN, PNUMBER}  ENAME is not a full FD (it is called a partial dependency ) since SSN  ENAME also holds A relation schema R is in second normal form (2NF) if every non-prime attribute A in R is fully functionally dependent on the primary key R can be decomposed into 2NF relations via the process of 2NF normalization

10. Introduction to Databases 10 Examples Second Normal Form

11. Introduction to Databases 11 Second Normal Form Note: The test for 2NF involves testing for functional dependencies whose left-hand side attributes are part of the primary key. If the primary key contains a single attribute, the test need not be applied at all.

12. Introduction to Databases 12 Third Normal Form Definition  Transitive functional dependency – a FD X  Y in R is a transitive dependency if there is a set of attributes Z that are neither a primary or candidate key and both X  Z and Z  Y holds. Examples:  SSN  DMGRSSN is a transitive FD since SSN  DNUMBER and DNUMBER  DMGRSSN hold  SSN  ENAME is non-transitive since there is no set of attributes X where SSN  X and X  ENAME

13. Introduction to Databases 13 3 rd Normal Form A relation schema R is in third normal form (3NF) if it is in 2NF and no non-prime attribute A in R is transitively dependent on the primary key

14. Introduction to Databases 14 Examples Third Normal Form

15. Introduction to Databases 15 SUMMARY OF NORMAL FORMS based on Primary Keys