gistfile1.txt

create temporary table tmpBrands (
  `id` int(10) unsigned NOT NULL,
  `code` varchar(10) NOT NULL DEFAULT '',
  new_id int(10) unsigned NOT NULL
) ENGINE=InnoDB AUTO_INCREMENT=18 DEFAULT CHARSET=utf8;

insert into tmpBrands 
	SELECT b.id, b.code, (
		SELECT b1.id
			FROM brands b1
			LEFT OUTER JOIN brands b2 ON (
				b1.code = b2.code 
				AND b1.id > b2.id)	
			where b2.id is null and UPPER(b1.code) = UPPER(b.code)
		)
	from brands b;

update accounts a set a.brand_id = (select b.new_id from tmpBrands b where b.id = a.brand_id);