need a guide to create a drop down menu navigation

[fandhie]

guys,
i really need a help with what I'm working at.

(first : sorry for my bad english, just hopping u understand what i want to ask here 🙂 )
I'm trying to make a drop down menu navigation for my website based on category and subcategory table.

I made two table to save the news category and sub category as follow :

-- Table structure for table `category`

CREATE TABLE IF NOT EXISTS `tb_cat` (
  `cat_id` int(11) NOT NULL AUTO_INCREMENT,
  `cat_name` varchar(225) NOT NULL,
  `cat_sort` int(5) NOT NULL,
  PRIMARY KEY (`cat_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=13 ;

--

-- Table structure for table `subcategory`

CREATE TABLE IF NOT EXISTS `tb_sub` (
  `sub_id` int(11) NOT NULL AUTO_INCREMENT,
  `sub_name` varchar(225) NOT NULL,
  `cat_name` varchar(225) NOT NULL,
  `sub_sort` int(5) NOT NULL,
  PRIMARY KEY (`sub_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=13 ;

--

so, you can see that this two tables have a similiar field named cat_name

next I want to make drop down menu using these two tables like follow :

<ul>     

    <li><a href="#">Category 1</a> 
      <ul> 
        <li><a href="#">Sub Category 1a</a></li> 
        <li><a href="#">Sub Category 1b</a></li> 
        <li><a href="#">Sub Category 1c</a></li> 
      </ul> 
    </li> 
    <li><a href="#">Category 2</a> 
      <ul> 
        <li><a href="#">Sub Category 2a</a></li> 
        <li><a href="#">Sub Category 2b</a></li> 
     <ul>
    </li>
  </ul>

I dont find any hard trouble to make script for Category menu like follow :

<?php  

$categoryi=mysql_query("SELECT * FROM tb_cat ORDER BY cat_sort,cat_name"); 
$no=1;
while ($r=mysql_fetch_array($category))
	{	
	echo "
      <li><a href=>$r[cat_name]</a> 
      <ul><li><a href=>SUB CATEGORY</a></li>
      </ul> 
    </li>";
	$no++;
	}
?>        

But i've already spent hours (and it make me nuts :p ) to find how to create script for SUB Category menu as above. Please give me a clue ....