Java, MySQL, and populating forms dynamically

I have a form with two select boxes. I need to populate one select box based on the choice selected from the other select box. All my data is stored in MySQL database. I understand I have to use java for this. I tried following the tutorial at http://www.devshed.com/Server_Side/MySQL/JS_Arrays/page2.html#database I was very confused since they are using 3 different tables where I am using only one. This line confused me from the tutorial: $sql = "SELECT p.person_id, s.person_id, CONCAT(last_name,',',first_name) AS name, skill_id"; dont understand what s.person references since there is no person_id listed in table called: skills. Does anyone have a simple tutorial showing how to populate one select form box based on the selection made from another? -------- Linux User Mysql and PHP 4.0.3