mysql-指定的密钥太长；最大密钥长度为1000个字节

culrpit sql语句是：

    CREATE TABLE  `jos_core_acl_aro` (

 `id` INT( 11 ) NOT NULL AUTO_INCREMENT ,
 `section_value` VARCHAR( 240 ) NOT NULL DEFAULT  '0',
 `value` VARCHAR( 240 ) NOT NULL ,
 `order_value` INT( 11 ) NOT NULL DEFAULT  '0',
 `name` VARCHAR( 255 ) NOT NULL ,
 `hidden` INT( 11 ) NOT NULL DEFAULT  '0',
  PRIMARY KEY (  `id` ) ,
  UNIQUE KEY (  `section_value` ,  `value` ) ,
  KEY  `jos_gacl_hidden_aro` (  `hidden` )
  ) ENGINE = MYISAM DEFAULT CHARSET = utf8 AUTO_INCREMENT =11;

MySQL said:

   #1071 - Specified key was too long; max key length is 1000 bytes

来源和目标数据库为UTF8.我仍然不知道为什么会发生此错误:(

你的钥匙

UNIQUE KEY (  `section_value` ,  `value` ) ,

大小为(240240)* 3个字节,大于1000个限制