Mastering Database Management

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Data Modeling

First Normal Form

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Definition of First Normal Form (1NF):

First Normal Form (1NF) is a property of a relation in a relational database. A table is said to be in 1NF if it contains only atomic (indivisible) values and there are no repeating groups or arrays of data. Each column in a 1NF table must hold a single value, and each cell must be atomic, meaning it cannot contain a set of values or another table.

Example:

Consider a table that violates 1NF:

Table: StudentCourses

StudentIDCourses
1Mathematics, Physics, Chem
2Computer Science, Math
3Physics, Biology

This table violates 1NF because the “Courses” column contains multiple values separated by commas, forming a repeating group.

Converting to First Normal Form:

To bring the table into 1NF, we need to eliminate the repeating groups by creating a new table for courses and establishing a relationship between the two tables.

Table: Students

StudentID
1
2
3

Table: Courses

StudentIDCourse
1Mathematics
1Physics
1Chemistry
2Computer Science
2Mathematics
3Physics
3Biology

Now, each table holds atomic values, and the relationship between students and courses is represented. The “Courses” column in the original table is replaced by the new “Courses” table, adhering to the 1NF requirements.

Explanation:

  1. Atomic Values:
    • In the original table, the “Courses” column violates 1NF because it contains multiple courses in a single cell.
    • In the normalized tables, the “Course” column in the “Courses” table holds atomic values, ensuring that each cell contains a single course.
  2. Elimination of Repeating Groups:
    • The original table had repeating groups in the “Courses” column for each student.
    • In the normalized tables, the repeating groups are eliminated by creating a separate table for courses, and the relationship is established through the “StudentID” column.
  3. Table Structure:
    • The resulting structure adheres to 1NF principles, with each table containing atomic values, and relationships between tables are established using foreign keys.

By transforming the original table into two tables and organizing the data, we achieve First Normal Form compliance, providing a foundation for further normalization if needed.