First Normal Form (1NF) | normalization and its types

FIRST NORMAL FORM(1NF)

A relation is said to be in first normal form, if it satisfies the following rules.

1. There are no duplicate rows i.e. all the primary key attributes are defined.
2. There are no repeating groups in the table i.e. each rows and columns intersection contains one and only one value and not a set of vales.

The first normal form does not allows a relations to contain nested relations.

E.G-Consider a relation "record"

St_id	St_name	subject	marks
101	Amrit	Computer Economics Maths	98 56 43
102	Anupreet	Maths Eco	98 99

It is not in 1NF

  

HOW TO CONVERT IT INTO 1NF?

METHOD 1

STEP 1-To remove repeating values for a column the record relation is converted to a flat relation i.e. STU1 by repeating the pair having composite primary key (St_id,St_name)

STEP 2- For every entry in the table consequently removing the attribute record with its sub-ordinate attributes.

Relation "STU1"

St_id	St_name	subject	marks
101	Amrit	Computer	98
101	Amrit	Economics	56
101	Amrit	Maths	43
102	Anupreet	Maths	98
102	Anupreet	Eco	99

It is  in 1NF but this method  increases redundancy.

METHOD 2

Another method is to remove the attributes that violates the first normal form and place it in a separate relation along with the primary key.So, un-normalized relation("record") is decomposed into 2 sub-relations .

(stu_details),(stu_performance)

Relation (stu_details)

St_id	St_name
101	Amrit
102	Anupreet

Relation (stu_performance)

St_id	subject	marks
101	Computer	98
101	Economics	56
101	Maths	43
102	Maths	98
102	Eco	99

It is in 1NF.

Anomalies -Insertion,deletion and updation anomaly