Schema Design Checklist: Field Kit

The database is the hardest part of an app to change later. A handful of principles, applied up front, avoids most of the mistakes that compound.

Model the business

Name the real entities and give each its own table, one row per thingTables that mix concepts cannot represent how the business actually works.
Express one-to-many relationships with a foreign key on the many sideImplicit relationships let an order point at a customer who does not exist.
Add a join table for every many-to-many relationshipWithout one, links like orders to products get stuffed into lists nobody can query.
Store each fact in exactly one place and reference it elsewhereCopied data has several versions to update, and they end up contradicting each other.
Denormalize only after you have measured a real performance problemPremature duplication is how databases drift into disagreeing with themselves.