PHP应用：php无限分类使用concat如何实现

PHP实战
--  
-- Table structure for table `category` 
--  
 
CREATE TABLE `category` ( 
 `id` int(11) NOT NULL auto_increment, 
 `catpath` varchar(255) default NULL, 
 `name` varchar(255) default NULL, 
 PRIMARY KEY (`id`) 
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=11 ; 
 
--  
-- Dumping data for table `category` 
--  
 
INSERT INTO `category` VALUES (1, '0', '网站首页'); 
INSERT INTO `category` VALUES (2, '0-1', 'Linux OS'); 
INSERT INTO `category` VALUES (3, '0-1', 'Apache服务器'); 
INSERT INTO `category` VALUES (4, '0-1', 'MySQL数据库'); 
INSERT INTO `category` VALUES (5, '0-1', 'PHP脚本语言'); 
INSERT INTO `category` VALUES (6, '0-1-2', 'Linux 系统教程'); 
INSERT INTO `category` VALUES (7, '0-1-2', 'Linux 网络技术'); 
INSERT INTO `category` VALUES (8, '0-1-2', 'Linux 平安基础'); 
INSERT INTO `category` VALUES (9, '0-1-2-7', 'Linux LAMP'); 
INSERT INTO `category` VALUES (10, '0-1-3-10', 'apache Server');  

PHP实战
<? 
$conn = mysql_connect ( 'localhost', 'root', 'root' ); 
mysql_select_db ( 'test', $conn ); 
mysql_query ( 'set names UTF8' ); 
$sql = "select id,concat(catpath,'-',id) as abspath,name from category order by abspath"; 
$query = mysql_query ( $sql ); 
while ( $row = mysql_fetch_array ( $query ) )  
{ 
  //第一种展示办法 
  //$space = str_repeat ( '    ', count ( explode ( '-', $row ['abspath'] ) ) - 1 ); 
  //echo $space . $row ['name'] . '<br>';*/ 
   
  //第二种展示办法 
  $space = str_repeat ( '    ', count ( explode ( '-', $row ['abspath'] ) ) - 1 ); 
  $option .= '<option value="' . $row ['id'] . '">' . $space . $row ['name'] . '</option>'; 
} 
echo '<select name="opt">' . $option . '</select>'; 
?> 

PHP实战
select concat('颜','培','攀')
select `id`,`name`,concat(`id`,'-',`name`) as iname