位字段上的group_concat（）在Mysql中返回垃圾

Table Structure

CREATE TABLE `academicyears` (
  `id` smallint(5) unsigned NOT NULL AUTO_INCREMENT,
  `campusid` int(11) DEFAULT NULL,
  `academicyear` text NOT NULL,
  `month` tinyint(4) DEFAULT NULL,
  `flag` bit(1) DEFAULT b'1',
  PRIMARY KEY (`id`)
);
CREATE TABLE `academicyears`