Interdepent Select Boxes

[rmaad]

I would like to better understand how to code interdependent select boxes. Currently, I query the database joining two tables so the information on the web page will appear in one select box. Only this makes the select box becomes very very long.

Some codes:
<?php

....
//select the main category and sub-category
$partTypeSQL = "SELECT PC.Part_cat_id, PC.Part_cat_name, PCS.Part_cat_sub_id, PCS.Part_cat_sub_name
FROM Part_categories PC LEFT JOIN Part_categories_sub PCS USING (Part_cat_id) ORDER BY PC.Part_cat_name, PCS.Part_cat_sub_name";

$partTypeQuery = new query($dbObject, $partTypeSQL);

?>

<table cellpadding="8" cellspacing="0" border="0" >
<tr align="left">
<th align="right">Part Category:</th>
<td><select name="partCatSubId">
<option value="-1">Select a Category
<?php
for ($r=0; $r<$partTypeQuery->numrows; $r++)
{
$partTypeQuery->fetch_array();
printf("<option value=\"%d\"%s>%s: %s</option>\n",
$partTypeQuery->row_data['Part_cat_sub_id'],
$isSelected,
$partTypeQuery->row_data['Part_cat_name'],
$partTypeQuery->row_data['Part_cat_sub_name']
);
}
$partTypeQuery->close();
?>
</select>
</td>
...

Help is appreciated.

Thanks,

[johnnyv]

I have this problem also selects with 3500 items suck.

I have a sort of hack that works but is far from elegant.

i divide the select data into catergorys then create javascript arrays for each catagory

so i have a select with a list of catagories that calls a javascript function after an "onchange" event. the function populates a second select from the appropriate javascript array.