如何批量删除织梦dedecms里的垃圾留言？

CREATE TABLE `dede_guestbook` (  
  `id` mediumint(8) unsigned NOT NULL auto_increment,  
  `title` varchar(60) NOT NULL default '',  
  `tid` mediumint(8) NOT NULL default '0',  
  `mid` mediumint(8) unsigned default '0',  
  `posttime` int(10) unsigned NOT NULL default '0',  
  `uname` varchar(30) NOT NULL default '',  
  `email` varchar(50) NOT NULL default '',  
  `homepage` varchar(50) NOT NULL default '',  
  `qq` varchar(15) NOT NULL default '',  
  `face` varchar(10) NOT NULL default '',  
  `ip` varchar(20) NOT NULL default '',  
  `dtime` int(10) unsigned NOT NULL default '0',  
  `ischeck` smallint(6) NOT NULL default '1',  
  `msg` text,  
  PRIMARY KEY  (`id`),  
  KEY `ischeck` (`ischeck`)  
) ENGINE=MyISAM AUTO_INCREMENT=194 DEFAULT CHARSET=utf8  

select * from dede_guestbook where ischeck=0; 

运行SQL：select * from dede_guestbook where ischeck=1，共有3条记录，最大返回100条！

delete from dede_guestbook where ischeck=0;