CREATE TABLE `order` (
`id` char(16) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '' COMMENT '订单号',
`user_id` bigint(20) NOT NULL DEFAULT '0' COMMENT '用户id',
UNIQUE KEY `id` (`id`),
 KEY `user_id` (`user_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci COMMENT='订单表';

CREATE TABLE `user` (
`id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '用户id',
PRIMARY KEY (`id`),
`username` varchar(32) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '' COMMENT '姓名',
 `password` char(60) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '' COMMENT '密码',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=10009866 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci COMMENT='用户表'

public function user()
{
  return $this->belongsTo('Models\User');
}

public function user()
{
  return $this->belongsTo('Models\User', 'user_id', 'uid');
}

{
 "id": 17021423166486,
 "user_id": 10000003,
 "user": {
  "id": 10000003,
  "username": "",
 }
}