ALTER TABLE orders ADD CONSTRAINT FOREIGN KEY fk_orders_customers(customer_id) REFERENCES customers(customer_id); ALTER TABLE orders ADD CONSTRAINT FOREIGN KEY fk_orders_employees(employee_id) REFERENCES employees(employee_id) ; ALTER TABLE orders ADD CONSTRAINT FOREIGN KEY fk_orders_shippers(ship_via) REFERENCES shippers(shipper_id); ALTER TABLE order_details ADD CONSTRAINT FOREIGN KEY fk_order_details_products(product_id) REFERENCES products(product_id); ALTER TABLE order_details ADD CONSTRAINT FOREIGN KEY fk_order_details_orders(order_id) REFERENCES orders(order_id); ALTER TABLE products ADD CONSTRAINT FOREIGN KEY fk_products_categories(category_id) REFERENCES categories(category_id); ALTER TABLE products ADD CONSTRAINT FOREIGN KEY fk_products_suppliers(supplier_id) REFERENCES suppliers(supplier_id); ALTER TABLE territories ADD CONSTRAINT FOREIGN KEY fk_territories_region(region_id) REFERENCES region(region_id); ALTER TABLE employee_territories ADD CONSTRAINT FOREIGN KEY fk_employee_territories_territories(territory_id) REFERENCES territories(territory_id); ALTER TABLE employee_territories ADD CONSTRAINT FOREIGN KEY fk_employee_territories_employees(employee_id) REFERENCES employees(employee_id);