Can you name the main normal forms in relational databases?

The main normal forms (NF) in relational databases are rules that help structure data to eliminate redundancy and update anomalies.

1. First Normal Form (1NF)

   • All attributes are atomic (indivisible).
   • No repeating groups or arrays.

2. Second Normal Form (2NF)

   • Satisfies 1NF.
   • All non-key attributes depend fully on the entire composite key (if the key is composite).

3. Third Normal Form (3NF)

   • Satisfies 2NF.
   • No transitive dependencies between non-key attributes (i.e., non-key attributes do not depend on each other).

Sometimes, the following are also distinguished:

• Boyce-Codd Normal Form (BCNF) — a stricter version of 3NF.
• Fourth Normal Form (4NF) — eliminates multivalued dependencies.

Example: if a table contains information about students and their courses, normalization helps split data into "Students" and "Courses" tables to avoid duplication and ensure integrity.