Use CHECK constraints to enforce invariants

Use CHECK constraints to enforce invariants | BeforeMerge Rules | BeforeMerge

Why this matters

The database is the last line of defense. Rules enforced only in app code are silently bypassed by migrations, background jobs, other services, and manual edits. CHECK constraints make invalid states impossible regardless of who writes.

-- bad (relies on app validation)
price numeric, discount numeric
 
-- good
price numeric NOT NULL CHECK (price >= 0),
discount numeric NOT NULL DEFAULT 0 CHECK (discount BETWEEN 0 AND price)

Why This Matters

Related Rules

Catch this automatically on every PR

Why this matters