Давайте поговорим о производительности...

Вот структура таблицы vii_news
CREATE TABLE IF NOT EXISTS `vii_news` (
`ac_id` int(11) NOT NULL AUTO_INCREMENT,
`ac_user_id` int(11) NOT NULL,
`action_type` tinyint(4) NOT NULL,
`action_text` text NOT NULL,
`obj_id` int(11) NOT NULL,
`action_time` int(11) NOT NULL,
`for_user_id` int(11) NOT NULL,
`answer_text` text NOT NULL,
`link` varchar(200) NOT NULL,
PRIMARY KEY (`ac_id`),
KEY `for_fast_select1` (`ac_user_id`,`action_time`),
KEY `for_fast_select2` (`ac_user_id`,`action_type`,`action_time`),
KEY `for_user_id` (`for_user_id`),
KEY `obj_id` (`obj_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=0 ;

CREATE TABLE IF NOT EXISTS `vii_news` (
`action_text` text NOT NULL,
`action_time` varchar(50) NOT NULL,
`ac_id` int(11) NOT NULL AUTO_INCREMENT,
`ac_user_id` int(11) NOT NULL,
`action_type` tinyint(11) NOT NULL,
`obj_id` int(11) NOT NULL,
`author_user_id` int(11) NOT NULL,
`for_user_id` int(11) NOT NULL,
`fasts_num` mediumint(11) NOT NULL,
`title` varchar(50) NOT NULL,
`photo` int(11) NOT NULL,
`comments` int(11) NOT NULL,
PRIMARY KEY (`ac_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=0 ;

и какая тут проблема ты так и не ответил

CREATE TABLE IF NOT EXISTS `vii_news` (
`ac_id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`ac_user_id` int(11) unsigned NOT NULL,
`action_type` tinyint(4) unsigned NOT NULL,
`action_text` text NOT NULL,
`obj_id` int(11) unsigned NOT NULL,
`action_time` int(11) unsigned NOT NULL,
`for_user_id` int(11) unsigned NOT NULL,
`answer_text` text NOT NULL,
`link` varchar(200) NOT NULL,
PRIMARY KEY (`ac_id`),
KEY `for_fast_select1` (`ac_user_id`,`action_time`),
KEY `for_fast_select2` (`ac_user_id`,`action_type`,`action_time`),
KEY `for_user_id` (`for_user_id`),
KEY `obj_id` (`obj_id`),
KEY `action_time` (`action_time`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=27 ;