From PHPBB用户手册

记录版面订阅信息
CREATE TABLE `phpbb_forums_watch` (
  `forum_id` mediumint(8) unsigned NOT NULL default '0', // 被订阅的版面
  `user_id` mediumint(8) unsigned NOT NULL default '0', // 订阅者用户ID
  `notify_status` tinyint(1) unsigned NOT NULL default '0', // 通告状态: 
                //0=尚未通知,查看帖子后归零;  1=已经通知,他人发帖后设1
  KEY `forum_id` (`forum_id`),
  KEY `user_id` (`user_id`),
  KEY `notify_stat` (`notify_status`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin;