Define foreign keys for referential integrity

Define foreign keys for referential integrity | BeforeMerge Rules | BeforeMerge

Why this matters

Foreign keys let InnoDB guarantee that related rows exist and define cascade behavior on delete/update. Without them, application bugs leave orphaned child rows that corrupt reports and joins.

-- Bad: no constraint, order can reference a missing customer
CREATE TABLE orders (customer_id INT);
 
-- Good: enforced reference
CREATE TABLE orders (
  customer_id INT,
  FOREIGN KEY (customer_id) REFERENCES customers (id)
);

Why This Matters

Related Rules

Catch this automatically on every PR

Why this matters