Mysql转储还原失败:无法添加外键约束

我正在尝试恢复使用mysqldump创建的转储.恢复原状,我明白了

第63行的错误1215(HY000):无法添加外键约束

DROP TABLE IF EXISTS `channel_tags`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `channel_tags` (
  `channel_tag_id` bigint(20) NOT NULL AUTO_INCREMENT,
  `channel_id` bigint(20) NOT NULL,
  `tag_name` varchar(60) NOT NULL,
  PRIMARY KEY (`channel_tag_id`),
  KEY `channel_id_idx` (`channel_id`),
  KEY `tag_name_idx` (`tag_name`),
  CONSTRAINT `ct_channel_fk` FOREIGN KEY (`channel_id`) REFERENCES `channel_shard` (`channel_id`),
  CONSTRAINT `ct_tag_fk` FOREIGN KEY (`tag_name`) REFERENCES `tags` (`tag_name`)
) ENGINE=InnoDB AUTO_INCREMENT=833 DEFAULT CHARSET=utf8mb4;
/*!40101 SET character_set_client = @saved_cs_client */;

DROP TABLE IF EXISTS `tags`;
/*!40101 SET @saved_cs_client     = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `tags` (
  `tag_name` varchar(60) NOT NULL,
  `created_at` datetime DEFAULT NULL,
  `updated_at` datetime DEFAULT NULL,
  PRIMARY KEY (`tag_name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
/*!40101 SET character_set_client = @saved_cs_client */;

create table语句的顺序是相同的.

SHOW ENGINE INNODB状态\ G给了我这个:

------------------------
LATEST FOREIGN KEY ERROR
------------------------
2015-12-07 17:20:16 1ac30b000 Error in foreign key constraint of table sde/channel_tags:
 FOREIGN KEY (`tag_name`) REFERENCES `tags` (`tag_name`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8mb4:
Cannot find an index in the referenced table where the
referenced columns appear as the first columns, or column types
in the table and the referenced table do not match for constraint.
Note that the internal storage type of ENUM and SET changed in
tables created with >= InnoDB-4.1.12, and such columns in old tables
cannot be referenced by such columns in new tables.
See http://dev.mysql.com/doc/refman/5.6/en/innodb-foreign-key-constraints.html
for correct foreign key definition.

有人能让我知道这里发生了什么吗？