How JSP codes residing in js function works

Question

Hi,
I would like to check with you how JSP codes residing in js function works.
How can I get the 2nd select stmt executed based on the values retrieve from 1st select statement and the conditions pass in to this js function
How can I get the select statement to execute only when a condition is met.
The following is the codes. It is not executing the 2nd select statement. when I didnt put in the 2nd select stmt, i execute those codes in that portion
script
====
function test(obj, obj2) {
<%
sql_query = "SELECT a1, a2 , a3, a4, a5 "+
" FROM table_a ";
try {
rset = db.execSQL(sql_query);
catch(SQLException e){
System.err.println ("Error in query " +e);
%>
var po_ln_fnd = false
<% while (rset.next()) {
j_a1 = rset.getString("a1");
j_a2 = rset.getString("a2");
j_a3 = rset.getString("a3");
%>
if ((eval(obj2.value)== '<%=j_a1%>')) {
if ((obj.value == '<%=j_a2%>') ) {
<% j_a4 = rset.getString("a4");
j_a5 = rset.getString("a5");
sql_query = "SELECT b2, b3, b4 "+
" FROM table_b "+
" WHERE b1 = '"+j_a3+"' ";
try {
rset = db.execSQL(sql_query);
catch (SQLException e) {
System.err.println("Error in query " +e);
while (rset.next()) {
String j_b2 = rset.getString("j_b2");
String j_b3 = rset.getString("j_b3");
String j_b4 = rset.getString("j_b4");
%>
<%}>
}

Answer 1

what is the other alternative to produce the same results: (retrieve the data based on the value entered on screen, upon onChange, it will chk whether the condition met, if met, will retrieve data from another table and display on the screen - all this is done without the submit button being pressed)