Post on 04-Jan-2016
Slide 1
Chapter 03
The Relational Model and Normalization
Slide 2
Content
A. Sales Receipt ProblemB. Solution
Slide 3
A. Sales Receipt Problem
DS company wants to store information of receipt for each selling time.
Each receipt has following information: Receipt ID Customer ID Customer Name Customer Address
Date of Receipt Each receipt has one or more receipt items which have
following information: Product ID
Product NameQuantityPrice Line Total
For more information about a receipt, please refer to next slide:
Slide 4
Let’s design the DB into Normal Form for the above requirement.
Next slides are some examples of receipt.
Line TotalPriceQuantityNameProduct ID
DS Company
ID: …… RECEIPTDate: ……….
Customer Name: …………………Customer ID: …………Address: ……………………………………………………..
Total
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Example 1:
Line TotalPriceQuantityNameProduct ID
DS Company
ID: PN001 RECEIPTDate: 04/12/2008.
Customer Name: Mr. Johnson. Customer ID: CUS001Address: New York
Coca Cola 100 100 10000 USD
PRO001
Total 10000 USD
Slide 6
Example 2:
PRO002
Line TotalPriceQuantityNameProduct ID
DS Company
ID: PN002 RECEIPTDate: 04/14/2008.
Customer Name: Mr. Stewart. Customer ID: CUS002Address: New York
Coca Cola 100 100 10000 USD
PRO001
7 up 100 5000 USD50
Total 15000 USD
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B. Solution
1. Logical Design2. Physical Design3. Relational Model Terminologies4. Normal Form
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1. Logical Design
Base on the requirement of problem, we have :o There are two objects: Receipt and Receipt_Items.o Each Receipt has one or more Receipt_Items.
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Delete attributes of each object don’t need to store data.
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In the above design, there is a problem called Data Duplication at Receipts Object.
To solve the problems: Attributes CustomerID, CustomerName and CustomerAddress should be move to new object (Customers).
Sample data
ReceiptsRecei
pt ID
Customer ID
Customer Name
Customer Address
Receipt Date
1 C0001Nguyen Thi Nga 702 Nguyen Kiem
22/4/2009 8:20 AM
2 C0378Tran The Nhan
103 Tran Hung Dao
22/4/2009 9:00 AM
3 C0001Nguyen Thi Nga 702 Nguyen Kiem
22/4/2009 7:20 PM
Customer Object
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Logical Diagram (ERD)
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Receipt_ItemsReceipt
IDProduct
IDProduct Name
Product Quantity
Product Price
1 PRO001 Coca Cola 10 1001 PRO002 7 UP 20 502 PRO001 Coca Cola 5 1003 PRO001 Coca Cola 8 100
In the above design, there is aslo a problem called Data Duplication at Receipt_Items Object.
To solve the problem: Attributes ProductID and ProductName should be move to new object (Products).
Sample data
ReceiptsReceipt
IDCustomer
ID Receipt Date
1 122/4/2009 8:20
AM
2 222/4/2009 9:00
AM
3 122/4/2009 7:20
PM
Product Object
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Logical Diagram(ERD)
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Another design
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2. Physical Design
Diagram for the first design
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Diagram for the second design
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3. Relational Model Terminology
3.1. Key definition3.2. Functional dependency3.3. What is determinant?
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3.1. Key definition
3.1.1. Primary key3.1.2. Compound key3.1.3. Surrogate key3.1.4. Candidate key3.1.5. Foreign key
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3.1.1. Primary key
PRIMARY KEY: the primary means of identifying rows in a relation:
• There is one and only one primary key per relation• The primary key may be a composite key• The ideal primary key is short, numeric and never
changes
Example: In the Receipts table, Receipt_ID is the PRIMARY KEY. (
)
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3.1.2. Compound key
COMPOUND KEY: is a primary key that consists of two or more columns.
Example: In the Receipt_Items table, Receipt_ID and Product_ID
combine together to become the COMPOUND KEY. ( )
Slide 15
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3.1.3. Surrogate key
SURROGATE KEY: as an artificial column added to a relation to serve as a primary key.
• A key with no business meaning• Short, numeric and never changes • Normally hidden in forms and reports• Frequently a sequential number
Identity: SQLServer Sequence: Oracle Auto_increment: MySQL
Autonumber: Microsoft Access ...
Examples: In the Receipt_Items table, ReceiptItem_ID is the
SURROGATE KEY . ( )
In the Receipts table, Receipt_ID is the SURROGATE KEY. ( )
Slide 16 Slide
15
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3.1.4. Candidate key
CANDIDATE KEY: is a key that determines all of the other columns in a relation.
Examples: In the Customers table, CustomerID is the CANDIDATE
KEY . ( )
In the Products table, ProductID is the SURROGATE KEY. ( )
Slide 16 Slide
16
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3.1.5. Foreign key
FOREIGN KEY: is the primary key of one relation (table) that is placed in another relation (table) to form a link between the relations:
A foreign key can be a single column or a composite key
The term refers to the fact that key values are foreign to the relation in which they appear as foreign key values
ExampleIn the Receipt_Items table, Receipt_ID is the FOREIGN KEY. ( )
Slide 16
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3.2. Functional dependency
In the Receipts table, ReceiptDate is functionally dependent on Receipt_ID. Given a value of Receipt_ID, you can determine the ReceiptDate. This is the example of Functional Dependency and can be written:
• Receipt_ID ReceiptDate
A functional dependency occurs when the value of one (a set of) attribute(s) determines the value of a second (set of) attribute(s).
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3.3. What is determinant?
The attribute on the left side of the functional dependency is called the determinant.
Example:Receipt_ID ReceiptDate
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4. Normal Form
4.1. First Normal Forms Definition4.2. Second Normal Forms Definition4.3. Third Normal Forms Definition
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4.1. First Normal Forms Definition
1NF – A table that qualifies as a relation is in 1NF. It means the table reaches the characteristics of relation
Characteristics of Relation: Rows contain data about an entity Columns contain data about attributes of the entities All entries in a column are of the same kind Each column has unique name Cells of the tables hold a single value The orders of the columns is unimportant The orders of the rows is unimportant No two rows may be identical
Example: Slide 8, slide 9
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4.2. Second Normal Forms Definition
2NF- A relation is in 2NF if all of its non-key attributes are dependent on ALL of the primary key.
Example: Slide 11
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4.3. Third Normal Forms Definition
3NF – A relation is in 3NF if it is in 2NF and has NO DETERMINANTS except the primary key.
Example: Slide 13, 14 in logical diagram or diagram below in physical diagram. It conforms to 3NF.
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