php - Display results on combobox by selecting a value on another combobox -

i have problem in project. have these categories:

football basketball tennis 

and these sub categories:

super league super league b euroleague serie 

i have categories , sub categories in phpmyadmin db. have code now, display these two, in 2 different comboboxes, via queries db:

<?php $category = mysql_query("select * katigories order id_katigoria"); echo "<select name='katigoria'>"; echo "<option selected='selected' value='0'> Επιλογή κατηγορίας! </option>"; while($values = mysql_fetch_assoc($category)) {     echo "<option value='$values[id_katigoria]'>".$values['katigoria']."</option>"; } echo "</select>"; ?> 

and

<?php $category = mysql_query("select * upokatigories order id_upokatigoria"); echo "<select name='upokatigoria'>"; echo "<option selected='selected' value='0'> Επιλογή υποκατηγορίας! </option>"; while($values = mysql_fetch_assoc($category)) {     echo "<option value='$values[id_upokatigoria]'>".$values['katigoria']."</option>"; } echo "</select>"; ?> 

so far good. problem want select first 1 basketball, , want see euroleague second combobox.

i don't know js or jquery, believe between 2 of them answer looking for. right?

please ideas, continue, or suggestions, read , look?

p.s. found similar here, c# or/and python..so, hope not repeating other questions

you need jquery makes ajax call server bring new dropdown list. see here: http://www.codingcereal.com/2009/09/autopopulate-select-dropdown-box-using-jquery/