I have the following schema on MySQL 5.1

CREATE TABLE  `mytest` (
  `category` varchar(32) ,
  `item_name` varchar(255)
  KEY `key1` (`category`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1; 

category column is filled with like that [:parent_parent_cat_id][:parent_cat_id][:leaf_cat_id]

"10000200003000"

if you can search all of the under categories :parent_parent_category_id

SELECT * FROM mytest WHERE category LIKE "10000%";

it's using index key1;

but How to use index when I wanna search :parent_cat_id?

SELECT * FROM mytest WHERE category LIKE "%20000%";

Do you have a better solutions?