Mysql InnoDB表外键约束

CREATE TABLE `country` (
  `country_id` smallint(5) unsigned NOT NULL auto_increment,
  `country` varchar(50) NOT NULL,
  `last_update` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP,
  PRIMARY KEY  (`country_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `city` (
  `city_id` smallint(5) unsigned NOT NULL auto_increment,
  `city` varchar(50) NOT NULL,
  `country_id` smallint(5) unsigned NOT NULL,
  `last_update` timestamp NOT NULL default CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP,
  PRIMARY KEY  (`city_id`),
  KEY `idx_fk_country_id` (`country_id`),
  CONSTRAINT `fk_city_country` FOREIGN KEY (`country_id`) REFERENCES `country` (`country_id`) ON DELETE RESTRICT ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert into country(country_id, country) values(1, "china");
insert into city(city_id, city, country_id) values(200, "wenzhou", 1);

mysql> delete from country where country_id=1;
ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`test/city`, CONSTRAINT `fk_city_country` FOREIGN KEY (`country_id`) R
EFERENCES `country` (`country_id`))

因为DELETE RESTRICT，子表有，删除父表时提示出错

mysql> update country set country_id=1000 where country_id=1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from country;
+------------+---------+---------------------+
| country_id | country | last_update         |
+------------+---------+---------------------+
|       1000 | china   | 2009-01-10 22:46:42 |
+------------+---------+---------------------+
1 row in set (0.00 sec)

mysql> select * from city;
+---------+---------+------------+---------------------+
| city_id | city    | country_id | last_update         |
+---------+---------+------------+---------------------+
|     200 | wenzhou |       1000 | 2009-01-10 22:45:38 |
+---------+---------+------------+---------------------+
1 row in set (0.00 sec)

mysql> show table status like 'city' \G;
*************************** 1. row ***************************
           Name: city
         Engine: InnoDB
        Version: 10
     Row_format: Compact
           Rows: 1
 Avg_row_length: 16384
    Data_length: 16384
Max_data_length: 0
   Index_length: 16384
      Data_free: 0
 Auto_increment: 201
    Create_time: 2009-01-10 22:36:53
    Update_time: NULL
     Check_time: NULL
      Collation: utf8_general_ci
       Checksum: NULL
 Create_options:
        Comment: InnoDB free: 4096 kB; (`country_id`) REFER `test/country`(`country_id`) ON UPDATE
1 row in set (0.00 sec)