1. Normal Forms in Relational Databases 1 1 Bolstad, P. pp 283-291

2. Problem Massive tables with information about multiple entities become unwieldy making data update and maintenance difficult. They suffer from performance issues, consistency, and redundancy

3. Problem Redundancy: Alderman Johnson in twice Access:linear search to find parcels owned by Yamane Independence:If Devlin, Yamane and Prestovic sell the parcel they jointly own Devlin is purged from the database!

4. Solution: Normalization Data structured in sequentially higher orders of normal form to: –improve consistency –Reduce redundancy –Increase stability

5. Definitions Supper key: one or more attributes that may be used to uniquely id one and only one record Candidate key is a subset of the supper key which may also be a superkey. Primary key chosen from candidate keys that has a one to one correspondence to each record Functional dependency –For a given point in time each value of the dependent attribute is determined by a value of another attribute. Own_name -> Own-add Tshp_name -> Thall-add Transitive

6. 1 st NF A table is in first normal form when there are no repeat columns –Most basic and still suffers from excessive storage, redundancy, inefficient searches and potential loss of data upon updating

7. 2 nd NF In 1 st NF form and every non-key attribute is functionally dependent on the primary key. Note in 1 st NF parcel-ID, Alderman and Tship-ID are duplicated when there are multiple owners of a parcel. Upon update of say Alderman, each redundant record needs to be updated.

8. First to Second NF Parcel – ID -> Alderman Parcel – ID -> Tship-ID Parcel – ID -> Tship_Name Parcel – ID -> Thall_add Own-ID -> Own_name Own-ID -> Own_add Link of two

9. Still a problem with 2 nd NF The 2 nd NF still has problems though it’s much better than 1 st. The problem is transitive dependency. In our table Land Record 1, Parcel-ID specifies Tship- ID and Tship-ID specifies Tship_nam and Thall_add, so: –Parcel-ID -> Tship-ID, Alderman –And –Tship-ID -> Tship-nam, Thall-add –If we delete a parcel we remove the parcel from tables Land Records 1 and Land Records 3 and loose relationship between Tship-ID, Tship_name and Thall_add.

10. Solution: 3 rd NF A table is in third normal fom if and only if for every functional dependency A-> B, A is a superkey or B is a member of a candidate key. Must ID all transitive functional dependencies and remove then by creating new tables

11. Example