What are normal forms and what types exist?

Normal forms are a set of rules and requirements for organizing data in relational databases to minimize redundancy and prevent update anomalies.

The main normal forms:

1. First Normal Form (1NF) — all fields contain atomic (indivisible) values, and the table does not contain repeating groups.

2. Second Normal Form (2NF) — the table is in 1NF, and all non-key attributes depend fully on the entire composite key (if the key is composite).

3. Third Normal Form (3NF) — the table is in 2NF, and all non-key attributes depend only on the key, without transitive dependencies.

4. Boyce-Codd Normal Form (BCNF) — an enhanced version of 3NF, where for every functional dependency, the determining attribute is a key.

Example: if a table has fields {Student, Course, Instructor}, and the instructor depends on the course, then to eliminate the transitive dependency, the table should be split into two: one with courses and instructors, and another with students and courses.

Normalization helps create more efficient and logical data structures, facilitating maintenance and development of the database.