Which normal form is typically used when creating a physical model: Third Normal Form, Second Normal Form, or Fourth Normal Form?

When designing a physical database schema, the goal is to eliminate redundancy while maintaining performance. The most common practice is to normalize the design to Third Normal Form (3NF). 3NF ensures that every non‑key attribute is not only dependent on the primary key but also independent of other non‑key attributes, eliminating transitive dependencies. This level of normalization strikes a balance between data integrity and query efficiency. Second Normal Form (2NF) removes partial dependencies but still allows transitive ones, which can lead to anomalies. Fourth Normal Form (4NF) addresses multi‑valued dependencies and is rarely required for typical OLTP systems because it can overly fragment tables and hurt performance. In practice, designers often start with 3NF and then apply denormalization or performance tuning (e.g., indexing, materialized views) as needed. Thus, 3NF is the standard normal form enforced when creating a physical model.