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Showing posts with label Normal Forms. Show all posts
Showing posts with label Normal Forms. Show all posts

## Set of solved exercises in Normalization / Normalization Solved Examples / How to find candidate keys, and primary keys in database? / Sets of examples to find the keys of a tables / Process of Key finding in a database - Examples / Normalization to 1NF, 2NF, 3NF

Let us assume a table User_Personal as given below;

 UserID U_email Fname Lname City State Zip MA12 Mani@ymail.com MANISH JAIN BILASPUR CHATISGARH 458991 PO45 Pooja.g@gmail.co POOJA MAGG KACCH GUJRAT 832212 LA33 Lavle98@jj.com LAVLEEN DHALLA RAIPUR CHATISGARH 853578 CH99 Cheki9j@ih.com CHIMAL BEDI TRICHY TAMIL NADU 632011 DA74 Danu58@g.com DANY JAMES TRICHY TAMIL NADU 645018
• Is this table in First Normal Form?
Yes. All the attributes contain only atomic values.

• Is this table in Second Normal Form?
To verify this property, we need to find all the functional dependencies which are holding in User_Personal table, and have to identify a Primary key.
Let us do that by using the sample data. This leads to the following set of FDs;
F = { UserID U_email Fname Lname City State Zip,
Zip City State }
As UserID attribute can uniquely determine all the other attributes, we can have UserID as the Primary key for User_Personal table.
The next step is to check for the 2NF properties;
Property 1 – The table should be in 1NF.
Property 2 – There should not be any partial key dependencies.

Our table is in 1NF, hence property 1 is holding.
Primary key of our table is UserID and UserID is single simple attribute. As the key is not composite, there is no chance for partial key dependency to hold. Hence property 2 is also holding.
User_Personal table is in 2NF.

• Is User_Personal in 3NF?
To verify this we need to check the 3NF properties;
Property 1 – Table should be in 2NF.
Property 2 – There should not be any Transitive Dependencies in the table.

Table User_Personal is in 2NF, hence property 1 is satisfied.

User_Personal table holds the following Transitive dependency;

UserID Zip, Zip City State

Hence, property 2 is not satisfied and the table is not in 3NF.

Solution:
Decompose User_Personal. For this, we can use the functional dependencies Zip City State and UserID U_email Fname Lname City State Zip.

As a result, we can have the following tables (primary keys are underlined);

User_Personal (UserID, U_email, Fname, Lname, Zip)
City (Zip, City, State)

 UserID U_email Fname Lname Zip MA12 Mani@ymail.com MANISH JAIN 458991 PO45 Pooja.g@gmail.co POOJA MAGG 832212 LA33 Lavle98@jj.com LAVLEEN DHALLA 853578 CH99 Cheki9j@ih.com CHIMAL BEDI 632011 DA74 Danu58@g.com DANY JAMES 645018
Table - User_Personal

 Zip City State 458991 BILASPUR CHATISGARH 832212 KACCH GUJRAT 853578 RAIPUR CHATISGARH 632011 TRICHY TAMIL NADU 645018 TRICHY TAMIL NADU
Table – City

Both tables are in 3NF.
Hence, tables are normalized to Third Normal Form.

**********

2nf normalized

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