Test cascade delete behavior

Verify that deleting an order cascades to its order_items, and that orders with payments are protected.

1. 1Delete the lowest-id cancelled order: DELETE FROM orders WHERE id = (SELECT MIN(id) FROM orders WHERE status = 'cancelled').
2. 2Confirm its order_items disappeared with it (ON DELETE CASCADE).
3. 3Try to delete the lowest-id delivered order; payments reference it without cascade, so it must fail.
4. 4Verify no orphans: SELECT COUNT(*) AS orphan_items FROM order_items i LEFT JOIN orders o ON o.id = i.order_id WHERE o.id IS NULL returns 0.

• Exactly one cancelled order and its items were deleted
• Deleting the delivered order fails with FOREIGN KEY constraint failed
• The last result set shows 0 orphaned order_items

• Every run starts from a freshly seeded database, so your script must include its own setup statements.
• A failing statement is recorded and the script keeps running, so you can trigger an error and verify afterwards.
• Only the last result set of your script is compared, so finish with the verification query.