DBMS Lecture 8 - Normalization

Lec 08: Normalization
BCA 20: DATABASE MANAGEMENT SYSTEM
AND PROGRAMMING
Department of Information Systems
College of Computer Studies
Xavier University – Ateneo de Cagayan

Review
1. What is a Table?
2. What is a Column?
3. What is a Row?

The Apparel Store Case Study
In preparation for next
year’s sale event, a
certain apparel shop is
coming up with ideas for
the Item database.
Analyze the table on the
succeeding slide, and see
how you can improve on it.

tbl_Items
Item Colors Price Tax
T-shirt Red 12.00 0.60
Polo Red 12.00 0.60
Sweatshirt Blue 12.00 0.60

Anomalies
The above table might be sufficient for a simple database,
but later on, errors (or anomalies) can occur when using it.
There are three general types of anomalies: Updation,
Insertion, and Deletion.

tbl_Items
T-shirt Red,blue 12.00 0.60
Polo Red, Yellow 12.00 0.60
T-shirt Red, Black 12.00 0.60
Sweatshirt Blue, Black 12.00 0.60

Updation Anomaly
For example, to update the colors of the item where it
occurs twice or more than twice in a table, we will have to
update column in all the rows, or else data will become
inconsistent.

Insertion Anomaly
Suppose for a new item, we have the item and color of the
item but if it has not opted for a price yet then we have to insert
NULL in there, leading to an Insertion Anomaly.

Deletion Anomaly
Likewise, if one item was suggested to be drops, then
during the time when we delete that row, the entire item record
will have to be deleted along with it.

The Solution
Through Normalization, we can make sure that the data
are logically arranged. Usually there are 5 levels of normal
forms, but usually 3rd normal form is sufficient for most typical
database applications:
There are three steps in the Normalization process:
First Normal Form (1NF);
Second Normal Form (2NF); and
Third Normal Form (3NF)

Normalization
Normalization is a technique
of organizing data in a
database through the
systematic decomposition of
tables in order to eliminate
data redundancies and
anomalies.

Normalization
These anomalies refer to
Insertion, Updation, and
Deletion Anomalies.

Normalization
Normalization ensures that
redundant data is eliminated,
and data is logically stored
(i.e. data dependencies make
sense).

The Apparel Store Case Study
Let’s see how we can
apply normalization to the
Registrar’s database.

First Normal Form
In First Normal Form, no two Rows
of data must contain repeating
group of information (i.e each set
of column must have a unique or
single value).
Each table should be organized
into rows, and each row should
have a primary key.

The Primary Key
The Primary Key is a single column
(or a combination of two or more
columns) that uniquely identifies
each row.
We will use primary keys to help
us in the Normalization process.

First Normal Form
Remember, in First Normal Form,
each row must not have a column
in which more than one value is
saved (liked separated with
commas). Also, each row must be
unique and distinguished by a
primary key.
tbl_Student1NF will now look like
this:

First Normal Form
Table is not in 1st normal form
because:
- Multiple items in color field
- Duplicate records / no
primary key
SOLUTION:
BREAK IT DOWN

tbl_Items
T-shirt Red 12.00 0.60
T-shirt Blue 12.00 0.60
Polo Red 12.00 0.60
Polo Yellow 12.00 0.60
Sweatshirt Blue 12.00 0.60
Sweatshirt Black 12.00 0.60

Second
Normal Form
A table in Second Normal Form
must first be in First Normal Form,
and it must not have any partial
dependencies.
All non-key fields depend on all
components of the primary key,
guaranteed when primary key is a
single field.

Partial Dependency
A Partial Dependency refers to
non-key attributes which are only
dependent on part of the primary
key (aka the composite primary
key).
Let’s take a look at table and see
how this applies.

Second
Normal Form
Table is not in second normal form
because:
- PRICE and TAX depend on ITEM,
but not COLOR

tbl_ColorItem
Item Color
T-shirt Red
T-shirt Blue
Polo Red
Polo Yellow
Sweatshirt Blue
Sweatshirt Black
Item Price Tax
T-shirt 12.00 0.60
Polo 12.00 0.60
Sweatshirt 12.00 0.60
tbl_PriceItem

Third Normal Form
Tables in Third Normal Form must
first be in Second Normal Form,
and all non-prime attributes of
each table must be dependent on
the primary key.

Transitive
Dependency
A Transitive Dependency refers to
non key attributes which
dependent on another non key
attribute.

Third Normal Form
Tables in Third Normal Form must
first be in Second Normal Form,
and all non-prime attributes of
each table must be dependent on
the primary key.
Let’s look at a table again:

Third Normal Form
Tables are not in third normal form
because:
- TAX depends on PRICE, not ITEM

tbl_ColorItem
Item Color
T-shirt Red
T-shirt Blue
Polo Red
Polo Yellow
Sweatshirt Blue
Sweatshirt Black
Item Price
T-shirt 12.00
Polo 12.00
Sweatshirt 12.00
tbl_PriceItem
Price Tax
12.00 0.60
tbl_Tax

Name Assignment A Assignment B
Jeff Smith Article Summary Poetry Analysis
Nancy Jones Article Summary Reaction Paper
Jane Scott Article Summary Poetry Analysis
Table_Assignment

Problem:
Table is not in first normal form because:
- Assignment field repeating
- First and last name in one field
- No (guaranteed unique) primary key field

Solution:
Break down the field NAME
into First Name, and Last
Name.

tbl_Assignment
First Name Last Name Assignment 1 Assignment 2
Jeff Smith Article Summary Poetry Analysis
Nancy Jones Article Summary Reaction Paper
Jane Scott Article Summary Poetry Analysis

No Primary Key??
Ans: CREATE ANOTHER FIELD
in this case name it Student
ID

tbl_Assignment
Student ID First Name Last Name Assignment 1 Assignment 2
1 Jeff Smith
Article
Summary
Poetry
Analysis
2 Nancy Jones
Article
Summary
Reaction
Paper
3 Jane Scott
Article
Summary
Poetry
Analysis

Seems okay right?
Look again in the table

Solution:
Assignment field repeating
Solution:
Create a new fields
(Assignment ID &
Description)

tbl_Assignment
Student ID First Name Last Name Assignment ID Description
1 Jeff Smith A Article Summary
1 Jeff Smith B Poetry Analysis
2 Nancy Jones A Article Summary
2 Nancy Jones C Reaction Paper
3 Jane Scott A Article Summary
3 Jane Scott B Poetry Analysis

Table is not in 2NF since:
- Description does not
depend on Student ID

tbl_Student
Student ID
First
Name
Last
Name
1 Jeff Smith
2 Nancy Jones
3 Jane Scott
Student
ID
Assignment
ID
Description
1 A Article Summary
1 B Poetry Analysis
2 A Article Summary
2 C Reaction Paper
3 A Article Summary
3 B Poetry Analysis
tbl_Assignment

Table is not in 3NF since:
-Description does not depend
still on Student ID
-Data Repetition

tbl_Student
Student ID First Name
Last
Name
1 Jeff Smith
2 Nancy Jones
3 Jane Scott
Student
ID
Assignment
ID
1 A
2 A
3 A
1 B
3 B
2 C
tbl_Assignment
Assignment
ID
Description
1 Article Summary
2 Poetry Analysis
3 Reaction Paper
tbl_Descript

Normalization for Non-IT Professionals
While the process of Normalization can be tricky for non-IT
students and professionals, everyone should still be able to
create logically-sound databases in the Third Normal Form.

Summary
Normalization is the systematic decomposition of tables in order to
eliminate data redundancies and anomalies. There are three normal
forms: 1NF, 2NF, and 3NF.
A Primary Key is a single column (or a combination of two or more
columns) that uniquely identifies each row.
A Partial Dependency refers to non-key attributes which are only
dependent on part of the primary key.
A Transitive Dependency refers to non key attributes which dependent on
another non key attribute.

Exercise 1
Normalize the following “Pet_Health” table to 3NF:
Pet_ID Pet_Name Pet_Type Pet_Age Owner
771 Rover Dog 12 Sam Villa
204 Spot Dog 2 Anna Dy
348 Mrs Whiskers Cat 4 Sam Villa

Exercise 2
Item_ID Item_Name Item_Desc
Supplier_Na
me
Address PO_num PO_date
A101 BckBP
One box of
black ballpens
De Oro Office
Supplies
Cagayan de
Oro City
20986 12-11-2014
A102 BluBP
One box of
blue ballpens
De Oro Office
Supplies
Cagayan de
Oro City
20986 12-11-2014
P100 SBP
One ream of
short bond
paper
King Papers
Cagayan de
Oro City
1217
02-10-2011
P100 SBP
One ream of
short bond
paper
Office Depot Iligan City 21044 01-05-2015

End
References:
www.lib.ku.edu/instruction

DBMS Lecture 8 - Normalization

Recommended

More Related Content

What's hot (20)

Viewers also liked (11)

Similar to DBMS Lecture 8 - Normalization (13)

Recently uploaded (20)

DBMS Lecture 8 - Normalization