How do You Determine When a Database Schema is Fully Normalized?

Answer: A database schema is considered fully normalized when it reaches the Third Normal Form (3NF).

A database schema is fully normalized when it has been structured to reduce redundancy and dependency by dividing a database into multiple tables and defining relationships between them according to normalization rules.

Higher normal forms, up to the Fifth Normal Form (5NF) and the Domain-Key Normal Form (DKNF), address more complex scenarios.

1. 1NF (First Normal Form): In this form, each table has a primary key, and all values are atomic (no repeating groups or arrays).
2. 2NF (Second Normal Form): It is in 1NF and all non-key attributes are fully functional and dependent on the primary key.
3. 3NF (Third Normal Form): It is in 2NF and all attributes are only dependent on the primary key, not on any other non-key attribute (eliminating transitive dependency).
4. 4NF or BCNF(Boyce-Codd Normal Form): A table is in BCNF if, and only if, it is already in 3NF and every determinant is a candidate key.

A schema can advance to 5NF to manage multi-valued dependencies and join dependencies. Achieving full normalization, aims at eradicating data redundancy and update anomalies while preserving data integrity, depends on the specific data context.