Normalization in Databases

1NF (First Normal Form)

Definition: A table is in 1NF if it contains only atomic values, with each column having a single value per row. No repeating groups or arrays are allowed in any column.

Example:

Initial Table:

StudentID	Name	Subjects
1	Alice	Math, Science
2	Bob	Math, English

Converted to 1NF:

StudentID	Name	Subject
1	Alice	Math
1	Alice	Science
2	Bob	Math
2	Bob	English

2NF (Second Normal Form)

Definition: A table is in 2NF if it is already in 1NF, and all non-key attributes are fully dependent on the entire primary key (no partial dependency).

Example:

Initial Table:

StudentID	CourseID	StudentName	CourseName
1	101	Alice	Math
1	102	Alice	Science

Converted to 2NF:

Student Table:

StudentID	StudentName
1	Alice

Course Table:

CourseID	CourseName
101	Math
102	Science

Enrollment Table:

StudentID	CourseID
1	101
1	102

3NF (Third Normal Form)

Definition: A table is in 3NF if it is already in 2NF, and all non-key attributes are only dependent on the primary key (no transitive dependencies).

Example:

Initial Table:

StudentID	CourseID	CourseName	Instructor
1	101	Math	Dr. Smith
1	102	Science	Dr. Adams

Converted to 3NF:

Course Table:

CourseID	CourseName	Instructor
101	Math	Dr. Smith
102	Science	Dr. Adams

Student Table:

StudentID	StudentName
1	Alice

Enrollment Table:

StudentID	CourseID
1	101
1	102