如何在char列中保存Ascii码值为（128-255）的字符？：报错

现象：使用Char(X)更新或插入只能保存0-127码值的字符。不能保存码值128以上的字符值。
环境：Windows2003（SP2) MySQL Server 5.5.1（直接安装版）数据库字符集GBK。
C: >mysql -u root
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 92477
Server version: 5.5.14 MySQL Community Server (GPL)

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owners.
过程：
mysql> show create table test;
CREATE TABLE test (
  idtest int(11) NOT NULL,
  charset2 char(10) DEFAULT NULL,
  PRIMARY KEY (idtest)
) ENGINE=InnoDB DEFAULT CHARSET=gbk
mysql> update test set charset2=char(128) where idtest=2;
ERROR 1366 (HY000): Incorrect string value: '\x80' for column 'charset2' at row 1

但执行Select char(128)却不会出错。非常急，项目中需要用到（128-255)区间的字符，究竟是什么原因有朋友知道吗？