1. Functional Dependency, Normalization
INFO 340
Lecture 6
Functional Dependency, Normalization

2. DeMorgan’s Theorem
A AND B = A OR B
A OR B = A AND B

3. For the following questions, use DeMorgan’s theorem to write 2 alternative versions of the where clause. Use the relations Fig 3.3 (pg 80) in the book:
From the staff table, which staff are male or have a birthdate after Jan 1, 1952 ?
What are the clientno’s and maxrents where the preference type is a flat and the telephone # has a 0 as a first digit ?
Which clients had viewed property before May 15, 2004 and preferred a house?

4. “Spreadsheet Syndrome”?
When you use a spreadsheet program, you only really have one table.
This leads to duplication of data.
Order ID
Request Date
Vendor Name
Delivery Attention
Delivery Address
Delivery Box
Delivery Phone
Shipping Method
Tax Rate
Product Number
Product Description
Qty
Unit Size
Unit Price
Total
252101
:33:23
Dell Computer Corp
Michael Middlebrooks
Hlth Sci Bldg
BB-704 Seattle,,WA 98195
357470
Standard 9%
400 / 800 GB Data Cartridge for LTO Ultrium 3 Tapes - 15 pack
1.00
15 pack
491.39
535.62
350W Additional Power Supply, SP Only, for Dell AX150
each
299.25
326.18
253517
:13:00
Buy.com
HSB BB NE Pacific Street Seattle,WA
Second Day
PCI1394_2LP
Startech.com 2 Port IEEE-1394 FireWire Low Profile PCI Card with Digital Video Editing Kit - PCI1394_2LP
4.00 ea
21.26
92.69
253779
:39:02
Hlth Sci Bldg BB-704 Seattle,,WA 98195 A
CAT6 Snagless Tip Network Cable - Pink - 3 ft
12.00
6.15
80.44 A
CAT6 Snagless Tip Network Cable - Blue - 20 ft
2.00
15.83
34.51

5. Normalization
Goal: Every non-key column is directly dependent on the key, the whole key, and nothing but the key!
Goal: Reduce redundancies, less anomalies, and improve efficiency.

6. Functional Dependency & Normalization
How normalization can be used when designing a relational database.
The potential problems associated with redundant data in base relations.
The concept of functional dependency, which describes the relationship between attributes.
The characteristics of functional dependencies used in normalization.

7. Functional Dependency & Normalization
How to identify the most commonly used normal forms, namely First Normal Form (1NF), Second Normal Form (2NF), and Third Normal Form (3NF).

8. Functional Dependency & Normalization
Characteristics of a suitable set of relations include:
the minimal number of attributes necessary to support the data requirements of the enterprise;
attributes with a close logical relationship are found in the same relation;
minimal redundancy with each attribute represented only once with the important exception of attributes that form all or part of foreign keys.

9. What happens if normalization hasn’t occurred?
Data duplication
Multiple truths
Inability to separate entities
Difficulty to query
Multiple truths – If only one part is updated, may have conflicting information.
Inability to separate – If Staff & Branch are in the same table, with the staffID as the primary key, you can not create a branch without a staff member. Same if you need to remove a staff member, bye bye branch.

10. Functional Dependency
A  B if for each value of A there is associated exactly one value of B.
Or think of it mathematically: F(A) = B, A B
Example: Name  Date of Birth. That is for a given person’s name, there is only one DOB that is associated with them. On the other hand, a date does not functionally determine a person. Many people can be born on a given day.

12. Full functional dependency
Functional dependencies can work on sets, for example: (student_no, course_no)  instructor is valid.
A fully functional dependency is when you can not remove items from the first set (the A in AB) and maintain a functional dependency.
The above example is not a full functional dependency, because course_no instructor is a functional dependency.

13. Transitive Dependency
Important to recognize a transitive dependency because its existence in a relation can potentially cause update anomalies.
Transitive dependency describes a condition where A, B, and C are attributes of a relation such that if A → B and B → C, then C is transitively dependent on A via B (provided that A is not functionally dependent on B or C).

14. Transitive Dependency Example
Consider functional dependencies in the StaffBranch relation
staffNo → sName, position, salary, branchNo, bAddress
branchNo → bAddress
Transitive dependency, branchNo → bAddress exists on staffNo via branchNo.

15. Functional Dependency & Normalization
Main characteristics of functional dependencies used in normalization:
There is a one-to-one relationship between the attribute(s) on the left-hand side (determinant) and those on the right-hand side of a functional dependency.
Holds for all time.
The determinant has the minimal number of attributes necessary to maintain the dependency with the attribute(s) on the right hand-side.

16. Functional Dependency & Normalization

17. Normalization
Formal technique for analyzing a relation based on its primary key and the functional dependencies between the attributes of that relation.
Often executed as a series of steps. Each step corresponds to a specific normal form, which has known properties.
As normalization proceeds, the relations become progressively more restricted (stronger) in format and also less vulnerable to update anomalies.

18. Functional Dependency & Normalization

19. 1st Normalized Form
A relation in which the intersection of each row and column contains one and only one value.
Atomicity. Based upon you’re requirements, a column holds only one value.
Requirements are important. Again, an address maybe fine as one text string, but if it should be decomposed into house number, street, city, etc. then it needs to be.
The great NULL debate. Many hold that normalized tables can not have NULLs.

20. Examples of 1NF Let’s look at what’s not 1NF.
Imagine a table with names and telephone numbers. What if we need more than one telephone #?
Add the value to the existing field, maybe a string value separated by comma. Breaks 1NF
Fig in book
It is completely possible to be 1NF and have duplicate values carried over different rows. This is fixed in 2NF.

21. 2nd Normal Form
Based on the concept of full functional dependency.
A relation that is in 1NF and every non-primary-key attribute is fully functionally dependent on the primary key.

22. 2NF examples
Student
Class
Location
John
CSE 143
EEB 103
EE 131
Susie
INFO 340
MGH 238
MATH 124
PAR 104
While in 1NF form, it is not in 2NF form. Candidate Key {Student,Class} . Location is not fully functional dependent, since it is dependent only on Class.
Student
Class
John
CSE 143
EE 131
Susie
INFO 340
MATH 124
Remember, all candidate keys must be examined, even if a primary key has been chosen. Still not immune to update issues.
Class
Location
CSE 143
EEB 103
EE 131
INFO 340
MGH 238
MATH 124
PAR 104

23. 3rd Normal Form
Based on the concept of transitive dependency.
A relation that is in 1NF and 2NF and in which no non-primary-key attribute is transitively dependent on the primary key.

24. 3NF example
PublisherID
Name
Address
City
State
ZIP 1
Apress
2560 Ninth Street, Station 219
Berkeley CA
94710
PublisherID
Name
Address
ZIP 1
Apress
2560 Ninth Street, Station 219
94710
ZIP
City
State
94710
Berkeley CA
Looks good, but notice that City and State are really dependent on ZIP, not Publisher_ID.
A good way to find transitive functional dependencies is think to yourself. If I update this column, do I need to update others? In this case, updating the City column would require you to update the ZIP and possible the State column.
This example, though, hints that one of the dangers of normalization, that you can sometimes go too far..

25. Homework
13.1, 13.3,13.10,13.11

26. In First, Second, or Third Normal Form
Books
Lecture 6
Class Exercise
For every relation:
Identify all FD’s
Including transitive
2) Answer whether it is
In First, Second, or Third
Normal Form