Relational Data Modeling

The decisions a relational schema forces, and how to settle them so the database enforces what it can and the application is left with only what it must. Every rule names the wrong default it corrects; there is no rule for what a capable model already gets right.

Examples are PostgreSQL 18, and every DDL statement in this skill was executed against 18.4 — including the failure cases, to confirm the constraints reject what they claim to reject. Roughly a third of the rules depend on mechanisms MySQL and SQLite do not have (EXCLUDE, partial unique indexes, range types, WITHOUT OVERLAPS, deferrable constraints, NOT VALID); those rules say so. The judgment rules transfer to any relational engine.

When to Apply

Use this skill when: