1. CSIS 115 Database Design and Applications for Business
Dr. Meg Fryling
“Dr. Meg”
Fall 2012
@SienaDrMeg
#csis115
© 2012 Meg Fryling

2. Agenda Chapter 3: The Relational Model and Normalization
Next Quiz (Monday, 11/19)
Minimum cardinality and referential integrity (including cascade updates and deletes)
How to enforce and what those constraints mean.
As usual, can have cheat sheet!

3. Normalizing for Data Integrity
Data integrity problems happen when data are duplicated
Normalized tables eliminate data duplication
General goal of normalization is to construct tables so every table has a single topic or theme
One fact – one place!
Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall

4. Normalization
Normalization: Process of converting a poorly structured table into two or more well-structured tables. Problem with these tables below is they have two independent themes: Employees and Department.
Table before update
Some rows show DeptNo 100 is “Accounting and Finance” and others show DeptNo 100 is “Accounting.” Which one is correct?
Table after update – what’s wrong?
Copyright © 2012 Pearson Education, Inc. Publishing as Prentice Hall

5. Normalization Steps
Create a new table for separate theme (repeated data).
Keep a copy of the new table’s primary key in the original table as a foreign key.
Create relationship between original and new table.

6. Each higher layer prevents a different update anomaly
Normal Forms
Each higher layer prevents a different update anomaly
A systematic way to remove update anomalies and improve data integrity
We move “up the ladder” from 0 NF
Each level (normal form) removes more anomalies
Since 3NF / BCNF (Boyce-Codd Normal Form) is easy to describe and fixes most update problems, we will focus on it.
5 NF & DKNF
Only in rare cases does a 3NF table not meet the requirements of BCNF. A 3NF table which does not have multiple overlapping candidate keys is guaranteed to be in BCNF.
BCNF ~ 3.5NF
4 NF
3 NF / BCNF
2 NF
1 NF
0 NF

7. Our Goal (BCNF)
Make any needed design changes so that every determinant in every table is a candidate key
Well, let’s define…

8. Candidate and Primary Keys
A candidate key is a key that functionally determines all of the other columns (fields) in a record.
A primary key is a candidate key selected as the primary means of identifying rows in a relation.
There is only one primary key per record.
The primary key may be a composite key.
The ideal primary key is short, numeric, and never changes (Chapter 6).
By definition… A candidate key of a relation will functionally determine all other attributes in the row
Likewise, by definition… A primary key of a relation will functionally determine all other attributes in the row
KROENKE AND AUER - DATABASE PROCESSING, 11th Edition © 2010 Pearson Prentice Hall

9. STUDENT Example
(SID, FirstName, LastName, Street, City, State, Zip, AdmissionTerm, SSN)
What are the candidate key(s)?
What would you use as the primary key?

10. Functional Dependency
A relationship between attributes in which one attribute (or group of attributes) uniquely determines the value of another attribute in the same table.
Example: The price of one cookie can determine the price of a box of 12 cookies
(CookiePrice, Qty)
BoxPrice
KROENKE and AUER - DATABASE CONCEPTS (3rd Edition)
© 2008 Pearson Prentice Hall

11. Determinants
The attribute (or attributes) that we use as the starting point (the variable on the left side of the equation) is called a determinant
(CookiePrice, Qty)
BoxPrice
Determinant
Functional Dependency
KROENKE and AUER - DATABASE CONCEPTS (3rd Edition)
© 2008 Pearson Prentice Hall

12. Composite Determinants
Composite determinant = a determinant of a functional dependency that consists of more than one attribute.
(CookiePrice, Qty)  (BoxPrice)
(SID, ClassID)  (Grade)
(EmployeeNumber, Phone)  (FirstName, LastName, Department, )
KROENKE AND AUER - DATABASE PROCESSING, 11th Edition © 2010 Pearson Prentice Hall

13. STUDENT Example
(SID, FirstName, LastName, Street, City, State, Zip, AdmissionTerm, SSN, DriversLicenseNum, DriversLicenseState)
What are the candidate key(s)?
What would you use as the primary key?

14. Functional Dependency Rules
If A  (B, C), then A  B and A C.
(SID)  (FirstName, LastName)
(SID)  (FirstName)
(SID)  (LastName)
If (A,B)  C, then neither A nor B determines C by itself (if it does then you are not in 2NF).
(SID, CourseID)  (Grade)
(SID) NOT  (Grade)
(CourseID) NOT  (Grade)

15. Functional Dependency Rule 1
If A  (B, C), then A  B and A C.
(EmployeeNumber, Phone)  (FirstName, LastName, Department, ) ?

16. Functional Dependency Rule 2: No Partial Key Dependencies
If (A,B)  C, then neither A nor B determines C by itself
(EmployeeNumber, Phone)  (FirstName, LastName, Department, )
FirstName, LastName, Department, and depend on EmployeeNumber alone!
Thus this table is not in 2NF !!
Any partial-key dependencies?

17. Functional Dependencies in the SKU_DATA Table
What are the functional dependencies?
KROENKE AND AUER - DATABASE PROCESSING, 11th Edition
© 2010 Pearson Prentice Hall

18. Functional Dependencies in the SKU_DATA Table
SKU  (SKU_Description, Department, Buyer)
SKU_Description  (SKU, Department, Buyer)
Buyer  Department
Buyers only have one department
Department NOT  Buyer
Multiple buyers for the same department
KROENKE AND AUER - DATABASE PROCESSING, 11th Edition © 2010 Pearson Prentice Hall

19. Functional Dependencies in the ORDER_ITEM Table
What are the functional dependencies?
KROENKE AND AUER - DATABASE PROCESSING, 11th Edition © 2010 Pearson Prentice Hall

20. Functional Dependencies in the ORDER_ITEM Table
(OrderNumber, SKU) 
(Quantity, Price, ExtendedPrice)
Because ExtendedPrice is a computed field, we also have:
(Quantity, Price)  (ExtendedPrice)
For a particular order and item there is only one quantity, price and extended price
KROENKE AND AUER - DATABASE PROCESSING, 11th Edition © 2010 Pearson Prentice Hall

21. Now you do it! Advisor Table
What are the functional dependencies?
What are the determinates?