By: Shiraj Mohamed M | MIS | SEUSL SHIRAJ MOHAMED M | MIS | SEUSL 1.
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Transcript of By: Shiraj Mohamed M | MIS | SEUSL SHIRAJ MOHAMED M | MIS | SEUSL 1.
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By: Shiraj Mohamed M | MIS | SEUSL
NORMALIZATION
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Basically, normalization is the process of structuring the tables in a database for maximum efficiencyNormalization involves creating tables and establishing relationships between those tables to make the database more flexible by eliminating redundancy and inconstancies.
NORMALIZATION
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SLNORMALIZATION…
• Conceptual Modeling is a subjective process
• Therefore, the schema after the logical database design phase may not be very good (contain redundant data)
• However, there are formalisms to ensure that the schema is good.
• This process is called Normalization
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SLNORMALIZATION…
• Relational database schema = set of relations
• Relation = set of attributes
• How we group the attributes to relations is very important
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S H I R A J M O H A M E D M | M I S | S E U S L
SCHEMA REFINEMENT….
DISCUSSED
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Determine Functional dependencies for relation
Find all keys in relation
Normalize the relation
SCHEMA REFINEMENT STEPS
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There are many Normal Forms proposed to reduce redundancies
Some of the well-known ones are:
1st Normal Form
2nd Normal Form
3rd Normal Form
Boyce-Codd Normal Form
NORMALIZATION….
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Superkey: Set of attributes S in relation R that can be used to identify
each tuple uniquely.
Key: A key is a superkey with the additional property that removal of any attributes from the key will not satisfy
the key condition
REVIEW OF SOME TERMS…
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Candidate Key: Each key of a relation is called a candidate key
Primary Key: A candidate key is chosen to be the primary key
Prime Attribute: an attribute which is a member of a candidate key
Nonprime Attribute: An attribute which is not prime
REVIEW OF SOME TERMS…
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Identify repeating groups of fieldsRemove repeating groups to a separate
tables.Identify the keys for the tables
FIRST NORMAL FORM (1NF)
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Check if all fields are dependent of the whole key
Remove Fields That depend on part of the key
Group Partially dependent fields as a separate table
Name the tablesIdentify keys to the tables
SECOND NORMAL FORM (2NF)
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Remove Fields That Depend on other non key attribute
Group interdependent fields as separate tables , identifies the key and
name the tables
THIRD NORMAL FORM (3NF)
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Cus iD Cus. Name
Cus. Address
Order No
Order Date
Item code
ItDesc Un.price
Qty
100 ABC Kadawatha A-10 10.4.09 C-1 Dhal 125.00
5
100 ABC Kadawatha A-10 10.4.09 C-5 Anchor 250.00
4
100 ABC Kadawatha A-10 10.4.09 C-10 Tea 140.00
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100 ABC Kadawatha A-10 104.09 F-4 Sunlight 30.00 5
100 ABC Kadawatha A-10 10.4.09 F-7 Vim 98.25 4
100 ABC Kadawatha A-10 10.4.09 F-10 Lux 35.00 5
100 ABC Kadawatha B-40 01.5.09 C-10 Tea 140.00
2
100 ABC Kadawatha B-40 01.5.09 F-4 Sunlight 30.00 1
100 ABC Kadawatha B-40 01.5.09 F-7 Vim 98.25 8
EXAMPLE
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Eliminate any duplicate or repeating columns or groups in the same table.
Since a Customer can place/have many orders, the above table now can be break into two.
Customer Details Table
FIRST NORMAL FORM (1NF)
Cus iD Cus. Name
Cus. Address
100 ABC Kadawatha
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Order Details Table
FIRST NORMAL FORM (1NF) …
Cus iD Order No
Order Date
Item code
ItDesc Un.price
Qty
100 A-10 10.4.11 C-1 Dhal 125.00
5
100 A-10 10.4.11 C-5 Anchor 250.00
4
100 A-10 10.4.11 C-10 Tea 140.00
6
100 A-10 104.11 F-4 Sunlight 30.00 5
100 A-10 10.4.11 F-7 Vim 98.25 4
100 A-10 10.4.11 F-10 Lux 35.00 5
100 B-40 01.5.11 C-10 Tea 140.00
2
100 B-40 01.5.11 F-4 Sunlight 30.00 1
100 B-40 01.5.11 F-7 Vim 98.25 8
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Eliminate redundant data.Now the table structure is improved. But you will notice that the Order Date is repeated.
So take that out from this table.
SECOND NORMAL FORM (2NF)
Cus iD Order No
Order Date
100 A-10 10.4.09
100 B-40 1.5.09
Improved Order Details Table
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Order-Item Table
SECOND NORMAL FORM (2NF)…
Order No
Item code
ItDesc Un.price
Qty
A-10 C-1 Dhal 125.00
5
A-10 C-5 Anchor 250.00
4
A-10 C-10 Tea 140.00
6
A-10 F-4 Sunlight 30.00 5
A-10 F-7 Vim 98.25 4
A-10 F-10 Lux 35.00 5
B-40 C-10 Tea 140.00
2
B-40 F-4 Sunlight 30.00 1
B-40 F-7 Vim 98.25 8
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Eliminate fields that do not depend on the primary key
You can notice that the Item Descriptions, Unit Price are not depend on the Oder No. So easily we can take them out from this
Order-Item table.
Improved Order-Item Table
THIRD NORMAL FORM (3NF)
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THIRD NORMAL FORM (3NF) …
Order No
Item code
Qty
A-10 C-1 5
A-10 C-5 4
A-10 C-10 6
A-10 F-4 5
A-10 F-7 4
A-10 F-10 5
B-40 C-10 2
B-40 F-4 1
B-40 F-7 8
Improved Order-Item Table
Item code
ItDesc Un.price
C-1 Dhal 125.00
C-5 Anchor 250.00
C-10 Tea 140.00
F-4 Sunlight 30.00
F-7 Vim 98.25
F-10 Lux 35.00
Item Details Table
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Now you will notice that all the details are simplified. So finally you will make
four (4) table to store these order details in the database. The tables will
be as follows
Cus iD Cus. Name
Cus. Address
100 ABC Kadawatha
Customer Details Table
Cus iD Order No
Order Date
100 A-10 10.4.09
100 B-40 1.5.09
Order Details Table
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Order No
Item code
Qty
A-10 C-1 5
A-10 C-5 4
A-10 C-10 6
A-10 F-4 5
A-10 F-7 4
A-10 F-10 5
B-40 C-10 2
B-40 F-4 1
B-40 F-7 8
Order-Item Table
Item code
ItDesc Un.price
C-1 Dhal 125.00
C-5 Anchor 250.00
C-10 Tea 140.00
F-4 Sunlight 30.00
F-7 Vim 98.25
F-10 Lux 35.00
Item Details Table
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EMP_PROJ
EXAMPLE02
SSN
PNUM HOURS
ENAME PNAME LOC
FD1
FD2
FD3
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SSN ENAME
EXAMPLE02…
SSN PNUM HOURS
PNUM PNAME PLOC
EP1
EP2
EP3
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EXAMPLE02…
ENAME SSN BDATE ADD DNUM DNAME DMGR
EMP_DEPT
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ED1
ED2
EXAMPLE02…
ENAME SSN BDATE ADD DNUM
DNUM DNAME DMGR
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Denormalization…Sometime for performance
reasons, database designer may leave the relation in a lower normal form.
This process is known as denormalization.
DENORMALIZATION
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S H I R A J M O H A M E D M | M I S | S E U S L
End…