CREATE TABLE `groups` (
  `group_id` int(11) NOT NULL AUTO_INCREMENT,
  `group` varchar(45) NOT NULL,
  PRIMARY KEY (`group_id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8

INSERT INTO `groups` (group_id,group) VALUES (1, 'group 1');
INSERT INTO `groups` (group_id,group) VALUES (2, 'group 2');

CREATE TABLE `items` (
  `item_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `group_id` int(10) unsigned DEFAULT NULL,
  `ident` varchar(45) NOT NULL,
  PRIMARY KEY (`item_id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8

INSERT INTO `items` (item_id,group_id,ident) VALUES (1,NULL,'item 1, no group');
INSERT INTO `items` (item_id,group_id,ident) VALUES (2,1,'item 2, g1');
INSERT INTO `items` (item_id,group_id,ident) VALUES (3,2,'item 3, g1');
INSERT INTO `items` (item_id,group_id,ident) VALUES (4,1,'item 4, g1');
INSERT INTO `items` (item_id,group_id,ident) VALUES (5,NULL,'item 5, no group');