Normal Form in MySQL


Hello everyone, previous article we learned Normalization and its advantages and disadvantages. In this article, we will learn Normal Form. Let’s go.



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There are six normal forms available in MySQL.
1.        1st Normal Form (1NF)
2.        2nd Normal Form (2NF)
3.        3rd Normal Form (3NF)
4.        Boyce-Codd Normal Form (BCNF)
5.        4th Normal Form (4NF)
6.        5th Normal Form (5NF)

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1.        1st Normal Form (1NF)
In First Normal Form (1NF) should have only single-valued attributes or each table cell should contain a single value. Each column needs to be unique records in first normal form.

For example: following fruits table 1 there is no First Normal Form (1NF) because of a multi-valued attribute in the fruits_names column.

Fruits Table 1:

No
fruits_colours
fruits_names
1
Red
Strawberries, Cherries, Apple
2
Yellow
Mango, Orange
3
Green
Kiwi


Fruits Table 2: following fruits table 2 there is first normal form because each cell has single values.

No
fruits_colours
fruits_names
1
Red
Strawberries
1
Red
Cherries
1
Red
Apple
2
Yellow
Mango
2
Yellow
Orange
3
Green
Kiwi


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2.        2nd Normal Form (2NF)
A Second Normal Form (2NF) it should be in the First Normal Form (1NF) and relation must not contain any partial dependency.

Fruit Information Table 1:

FINo
fruits_colours
fruits_names
1
Red
Strawberries
2
Red
Cherries
3
Yellow
Mango
4
Green
Kiwi


Fruit Color Category Table 2:

FINo
fruits_colours
1
Red
2
Yellow
3
Green

Fruit Name Table 3:
FNNo
fruits_names
1
Strawberries
2
Cherries
3
Mango
4
Kiwi

Fruit Table 4:

FNo
FINo
FNNo
1
1
1
2
1
2
3
2
3
4
3
4






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3.        3rd Normal Form (3NF)
A Third Normal Form (3NF) it should be in the Second Normal Form (2NF) and it has no Transitive Dependency.

4.        Boyce-Codd Normal Form (BCNF)
Third Normal Form (3NF) higher version is Boyce-Codd Normal Form (BCNF) and relation R must be in Third Normal Form (3NF). Boyce-Codd Normal Form (BCNF) for each functional dependency (x à y) x should be a super key. Boyce-Codd Normal Form (BCNF) is free from redundancy and if a relation is in Boyce-Codd Normal Form (BCNF), then Third Normal Form (3NF) is also satisfied.
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5.        4th Normal Form (4NF)
A Fourth Normal Form (4NF) it should be in the Boyce-Codd Normal Form (BCNF) and Fourth Normal Form (4NF) tables don’t have Multi-Valued Dependencies on a Primary Key.

6.        5th Normal Form (5NF)
A relation R is in Fifth Normal Form (5NF) if it is in Fourth Normal Form (4NF) and not contains any join dependency. Fifth Normal Form (5NF) can’t be further non-loss decomposed (join dependency).

So this is all about Normalizations six Normal Forms.             

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