CREATE TABLE `items` (
  `id` int(10) unsigned NOT NULL auto_increment,
  `unlocked` tinyint(1) NOT NULL default '0',
  `name` varchar(200) NOT NULL,
  `meta_cat_type` enum('blah','foo','bar') default NULL,
  `post_time` int(10) unsigned NOT NULL default '0',
  `unlock_time` int(10) unsigned NOT NULL,
  `allow_comments` tinyint(1) NOT NULL default '1',
  `posted_by` int(10) unsigned NOT NULL,
  PRIMARY KEY  (`id`),
  UNIQUE KEY `name` (`name`),
  KEY `post_time` (`post_time`),
  KEY `meta_cat_type` (`meta_cat_type`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- --------------------------------------------------------

CREATE TABLE `item_cats` (
  `item_id` int(10) unsigned NOT NULL,
  `cat_id` smallint(5) unsigned NOT NULL,
  KEY `item_id` (`item_id`),
  KEY `cat_id` (`cat_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- --------------------------------------------------------

CREATE TABLE `item_filters` (
  `user_id` int(10) unsigned NOT NULL,
  `cat_id` smallint(5) unsigned NOT NULL,
  `meta_cats` set('blah','foo','bar') NOT NULL,
  `filter_type` enum('overview','global') NOT NULL,
  UNIQUE KEY `id` (`user_id`,`cat_id`,`filter_type`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

SELECT COUNT( * )
FROM items
WHERE unlocked =1
AND (
  NOT EXISTS (
    SELECT * FROM item_filters f, item_cats c
    WHERE f.user_id = "823"
      AND f.cat_id = c.cat_id
      AND c.item_id = items.id
      AND f.filter_type = "overview"
      AND FIND_IN_SET( items.meta_cat_type, meta_cats )
)