GATE CS 1998 Q1.34 — Normal Forms

In practical relational database design, Third Normal Form (3NF) is considered the standard and adequate level of normalization for most applications.

Here is why:

• Dependency Preservation & Lossless Join: A decomposition into 3NF is always guaranteed to be both lossless and dependency-preserving. While Boyce-Codd Normal Form (BCNF) is stronger, it cannot always preserve all functional dependencies.
• Redundancy Control: 3NF eliminates most insertion, update, and deletion anomalies by ensuring that no non-prime attribute is transitively dependent on any candidate key.
• Practicality: Higher normal forms like 4NF (which addresses multi-valued dependencies) and 5NF (which addresses join dependencies) are rarely used in practice because the anomalies they prevent are uncommon, and the performance cost of joining many highly-decomposed tables is high.

Thus, 3NF strikes the best balance between performance and data integrity for typical database designs.