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1-NF form in DBMS
1-NF Form in DBMS
In this article, 1-NF Form in DBMS.
Normalization is a process of breaking a table into a much better table so that it is free from all the problems due to insertion update and deletion.
Learn more about Normalization here on this page.
First Normal Form(1NF)
- Definition: A table is said to be in First Normal Form if it is free from
multivalued or composite attributesi.e each attribute should be atomic
- A multivalued attribute is nothing but it contains more than one value in a single cell
Consider a table where a student can have multiple phone numbers
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
Eliminate the multivalued attribute by introducing a composite keyi.e roll number, phone number combination would act as a primary key
Normalized to 1NF
This approach causes serious drawback of update anomaly due to redundancy in the table (Prashant data stored redundantly)
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
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
Make each and every attribute as atomic i.e introduce n separate columns for n multivalues
Normalized to 1NF
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