Referential Integrity and Constraints¶

Encoding data rules as declarative constraints (not just application logic) ensures rules are enforced regardless of how data is modified, preventing invalid states at the source.

Tension Addressed¶

Data Integrity vs. Performance

Recognizable As¶

Foreign key constraints, check constraints, unique constraints, not-null constraints, cascading deletes/updates, constraint violation errors

Canonical Sources¶

Codd, "A Relational Model of Data" (1970); Date, "An Introduction to Database Systems"

Transfers To¶

Type systems (compile-time constraints), API validation, form validation, any system requiring data invariants

Application-level validation can be bypassed (direct database access, bugs, multiple applications); database-level constraints are the last line of defense.