Database Constraints | Alter Constraints MYSQL

-- declare not null each column at each table
  ALTER TABLE `order` CHANGE `order_date` `order_date` DATETIME NOT NULL;
  ALTER TABLE `order` CHANGE `order_payment` `order_payment` int(11) NOT NULL;
  ALTER TABLE `order` CHANGE `user_id` `user_id` char(5) NOT NULL;

  ALTER TABLE `order_detail` CHANGE `order_detail_amount` `order_detail_amount` int(11) NOT NULL;
  ALTER TABLE `order_detail` CHANGE `id_product` `id_product` char(4) NOT NULL;
  ALTER TABLE `order_detail` CHANGE `order_id` `order_id` char(15) NOT NULL;

  ALTER TABLE `product` CHANGE `product_name` `product_name` varchar(255) NOT NULL;
  ALTER TABLE `product` CHANGE `product_price` `product_price` int(11) NOT NULL;
  ALTER TABLE `product` CHANGE `product_amount` `product_amount` int(11) NOT NULL;

  ALTER TABLE `user` CHANGE `user_name` `user_name` varchar(255) NOT NULL;
  ALTER TABLE `user` CHANGE `user_phone` `user_phone` char(20) NOT NULL;
  ALTER TABLE `user` CHANGE `user_email` `user_email` varchar(255) NOT NULL;
  ALTER TABLE `user` CHANGE `user_password` `user_password` varchar(255) NOT NULL;
  ALTER TABLE `user` CHANGE `user_balance` `user_balance` int(12) NOT NULL;
  ALTER TABLE `user` CHANGE `user_status` `user_status` enum('unvalid','validated','disabled') NOT NULL;
  ALTER TABLE `user` CHANGE `user_role` `user_role` enum('customer','admin','cashier') NOT NULL;

-- declare key on teble Order
ALTER TABLE `order`
  ADD PRIMARY KEY (`order_id`),
  ADD KEY `user_id` (`user_id`);

-- declare key on teble Order_detail
ALTER TABLE `order_detail`
  ADD PRIMARY KEY (`order_detail_id`),
  ADD KEY `order_id` (`order_id`),
  ADD KEY `id_product` (`id_product`);

-- declare key on teble Product
ALTER TABLE `product`
  ADD PRIMARY KEY (`product_id`);

-- declare key on teble User
ALTER TABLE `user`
  ADD PRIMARY KEY (`user_id`),
  ADD UNIQUE KEY `user_phone` (`user_phone`),
  ADD UNIQUE KEY `user_email` (`user_email`);

-- declare constraints on teble Order
ALTER TABLE `order`
  ADD CONSTRAINT `order_ibfk_1` FOREIGN KEY (`user_id`) REFERENCES `user` (`user_id`);

-- declare constraints on table Order_detail
ALTER TABLE `order_detail`
  ADD CONSTRAINT `order_detail_ibfk_1` FOREIGN KEY (`order_id`) REFERENCES `order` (`order_id`),
  ADD CONSTRAINT `order_detail_ibfk_2` FOREIGN KEY (`id_product`) REFERENCES `product` (`product_id`);