how i conditional access the data from database using combo box.

i have combox box named class when i select its value 11 or 12, another combo box appears named Subject values Arts, Commerce, Science.

how i conditional access the data from database when i select class 11 0r 12.
Here is JSP file:-
display.jsp:

<html>
<head>
<body>
<form name="form" >
<table align="center">

<script language="javascript">
function sendData(){
var sch=document.form.school.value;
var cla=document.form.class_name.value;
var y1=document.form.from_year.value;
var y2=document.form.to_year.value;
window.open("show.jsp?class_name="+cla+"&&from_year="+y1+"&&to_year="+y2+"&&school="+sch);
alert(sch+" "+cla+ " "+y1+" "+y2);
}

function hide(){
if (document.getElementById){
document.getElementById('combo').style.visibility = 'hidden';
}
}
function call(class_name){
var val = class_name.options[class_name.selectedIndex].text;
if((val=='11')||(val=='12')){
document.getElementById('combo').style.visibility = 'visible';
var arr = new Array();
arr[11] = new Array("Art","Commerce","Science");
arr[12] = new Array("Art","Commerce","Science");
var comboValue = class_name.value;
document.forms["form"].elements["combo2"].options.length=0;
for (var i=0;i<arr[comboValue].length;i++)
{
var option = document.createElement("option");
option.setAttribute('value',i+1);
option.innerHTML = arr[comboValue][i];
document.forms["form"].elements["combo2"].appendChild(option);
}
}
else{
document.getElementById('combo').style.visibility = 'hidden';
}
}
</script>
<body onload="hide();">

<p></p><br><br><br><br><br><br>
<tr><td style="width: 11px"> <span>Class</td> <td><select name="class_name" onchange="call(this); >
<%

for( int i=1;i<=12;i++){
%>
<option value="<%=i%>"><%=i%></option>
<%
}
%>
</select><td>
<select id="combo" name="combo2">
</select></td>

<tr><td style="width: 11px"> <span>From Year</td><td><select name="from_year">
<%
for(int j=2000;j<=2010;j++){
%>
<option value="<%=j%>"><%=j%></option>
<%
}
%>
</select></td></tr>
<tr><td style="width: 11px"> <span>To Year</td><td><select name="to_year">
<%
for(int k=2000;k<=2010;k++){
%>
<option value="<%=k%>"><%=k%></option>
<% } %>
</select></td></tr><td></td>
<tr><td style="width: 11px"> <span><input type="button" value="Result" onclick="sendData();"></td></tr>
<tr><td><input type="hidden" name="school" value="<%=request.getParameter("school")%>"></td></tr>
</table>
</form>
</body>
</head>
</html>

kindly help.

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