# 1-NF form in DBMS

### About 1-NF Form in DBMS

Normalization is a process of breaking a table into you still optimized ones so that they are free from all problems faced due to insertion updation and deletion of data in the table

### First Normal Form(1NF)

• Definition: A table is said to be in First Normal Form if it is free from `multivalued or composite attributes `i.e each attribute should be atomic
• A multivalued attribute is nothing but it contains more than one value in a single cell

#### Problem Table:

Consider a table where a student can have multiple phone numbers

STUDENT

Roll no Name Phone
66 Trishaank P1
73 Prashant P2,P3
79 Sanjay P4
82 Srinivas P5
From the above figure, we can see that a cell is containing two values(two phone numbers) which breaks our rule This problem can be solved in three approaches

### Approach 1:

Eliminate the multivalued attribute by introducing a composite keyi.e roll number, phone number combination would act as a primary key

#### Problem Table

Roll no Name Phone
66 Trishaank P1
73 Prashant P2,P3
79 Sanjay P4
82 Srinivas P5

#### Normalized to 1NF

Roll no Name Phone
66 Trishaank P1
73 Prashant P2
73 Prashant P3
79 Sanjay P4
82 Srinivas P5

#### Drawback:

This approach causes serious drawback  of update anomaly due to redundancy in the table (Prashant data stored redundantly)

### Approach 2:

Divide the table into two parts such that all the multivalued attributes in one table at single-valued attributes in another table and add primary key attribute of the original table to each newly formed tables

Roll no Phone
66 P1
73 P2
73 P3
79 P4
82 P5

#### Student

Roll no Name
66 Trishaank
73 Prashant
79 Sanjay
82 Srinivas

In this example, multivalued attributes phone numbers and primary key attribute roll number will from one table and all the remaining single-valued attributes name and primary key attribute roll number will from another table

### Approach 3:

Make each and every attribute as atomic i.e introduce n separate columns for n multivalues

#### Problem Table

Roll no Name Phone
66 Trishaank P1
73 Prashant P2,P3
79 Sanjay P4
82 Srinivas P5

#### Normalized to 1NF

Roll no Name Phone1 Phone2 Phone3
66 Trishaank P1 ——– ——–
73 Prashant P2 P3 ——–
79 Sanjay P4 ——– ——–
82 Srinivas P5 ——– ——–

#### Drawbacks:

It’s it not necessary that each and every student would have multiple phone numbers, as a result, empty  cells have to be maintained which results in memory wastage

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