Glossary term
What is constraint? Meaning for developers
A rule the database enforces, such as NOT NULL, UNIQUE, CHECK or a foreign key.
Learn it properly · SQL & PostgreSQLLesson 4: Designing a Schema: Keys, Normalisation and ConstraintsIdentity versus UUID keys, normal forms with a flat-to-normalised redesign, ON DELETE, enums, money, timestamptz and soft deletes.