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First Normal Form (1NF) in DBMS



The First Normal Form (1NF) is the first step in the normalization process of organizing data within a relational database to reduce redundancy and improve data integrity. A relation (table) is said to be in 1NF if it adheres to the following rules:

1. Atomic Values:

  • Each attribute (column) contains only atomic (indivisible) values. This means values in each column are indivisible units and there should be no sets, arrays, or lists.
  • For example, a column called "Phone Numbers" shouldn't contain multiple phone numbers for a single record. Instead, you'd typically break it into additional rows or another related table.

2. Primary Key:

  • Each table should have a primary key that uniquely identifies each row. This ensures that each row in the table can be uniquely identified.

3. No Duplicate Rows:

  • There shouldn’t be any duplicate rows in the table. This is often ensured by the use of the primary key.

4. Order Doesn't Matter:

  • The order in which data is stored doesn't matter in the context of 1NF (or any of the normal forms). Relational databases don't guarantee an order for rows in a table unless explicitly sorted.

5. Single Valued Attributes:

  • Columns should not contain multiple values of the same type. For example, a column "Skills" shouldn't contain a list like "Java, Python, C++" for a single record. Instead, these skills should be split across multiple rows or placed in a separate related table.

Example for First Normal Form (1NF)

Consider a table with a structure:


| Student_ID | Subjects          |
|------------|-------------------|
| 1          | Math, English     |
| 2          | English, Science  |
| 3          | Math, History     |

The table above is not in 1NF because the "Subjects" column contains multiple values.

To transform it to 1NF:


| Student_ID | Subject   |
|------------|-----------|
| 1          | Math      |
| 1          | English   |
| 2          | English   |
| 2          | Science   |
| 3          | Math      |
| 3          | History   |

Now, each combination of "Student_ID" and "Subject" is unique, and every attribute contains only atomic values, ensuring the table is in 1NF.

Achieving 1NF is a fundamental step in database normalization, laying the foundation for further normalization processes to eliminate redundancy and ensure data integrity.

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