From PHPBB用户手册

# Table: 'phpbb_bookmarks'
CREATE TABLE phpbb_bookmarks (
	topic_id mediumint(8) UNSIGNED DEFAULT '0' NOT NULL, 被收藏的主题ID
	user_id mediumint(8) UNSIGNED DEFAULT '0' NOT NULL, 收藏者的用户ID
	PRIMARY KEY (topic_id, user_id)
) CHARACTER SET `utf8` COLLATE `utf8_bin`;