Many developers believe they need a relational database because their data has relationships. The reasoning usually goes: "My entities are related, therefore I need foreign keys, therefore I need an RDBMS." But the causality is actually reversed. Normalization creates the need for foreign keys—not the other way around. This misunderstanding persists when the builders are agents, because LLMs operate on high-dimensional similarity (vectors), which may catch correlation better than causality. Normalisation and relations When you normalize your domain model into Normal Forms, you decompose aggregates—cohesive groups of entities that form a natural consistency boundary—into separate, independent tables. Each table represents a single relation in the mathematical sense: a set of tuples (rows) constrained by functional dependencies on a key. That is what "relational" means in "relational model"—it refers to these mathematical relations (tables), not to the relationships between entities.…