我的数据库有三个表，下面要怎样再加一个下拉列表框，谢谢大家了！
大类：anclass
字段： 　　　数据类型：
anclassid 　　　int
anclass nvarchar
fudongjia int
changyong int
anclassidorder int
中类：nclass
nclassid 　　　int
nclass nvarchar
anclassid int
changyong int
nclassidorder int
小类：
nclassid 　　　int
nclass nvarchar
anclassid int
changyong int
nclassidorder 　int


<%
dim count
set rs=server.createobject("adodb.recordset")
rs.open "select * from shop_Nclass order by Nclassidorder ",conn,3,2%>
<script language = "JavaScript">
var onecount;//定义onecount对象
onecount=0; //初始值为0
subcat = new Array();//subcat对象是一个新的数组
<%
count = 0 '定义count对像初始值为0
do while not rs.eof
%>
subcat[<%=count%>] = new Array("<%= trim(rs("Nclass"))%>","<%= rs("anclassid")%>","<%= rs("Nclassid")%>");
<%
count = count + 1
rs.movenext
loop
rs.close
%>

onecount=<%=count%>;

function changelocation(locationid)
{
document.myform.Nclassid.length = 0;

var locationid=locationid;
var i;
for (i=0;i < onecount; i++)
{
if (subcat[i][1] == locationid)
{
document.myform.Nclassid.options[document.myform.Nclassid.length] = new Option(subcat[i][0], subcat[i][2]);
}
}

}

</script>
<form name="myform" method="post" action="saveaddbook.asp?action=add" OnSubmit="return checkkk()" >

<td width="21%" align="right">选择商品的分类：</td>
<td width="79%">
<%
rs.open "select * from shop_anclass order by anclassidorder",conn,3,2
if rs.eof and rs.bof then
response.write "请先添加栏目。"
response.end
else
%>
大类：
<select name="anclassid" size="1" id="anclassid" onChange="changelocation(document.myform.anclassid.options[document.myform.anclassid.selectedIndex].value)">
<option selected value="<%=rs("anclassid")%>"><%=trim(rs("anclass"))%></option>
<% dim selclass

selclass=rs("anclassid")
rs.movenext
do while not rs.eof
%>
<option value="<%=rs("anclassid")%>"><%=trim(rs("anclass"))%></option>
<%
rs.movenext
loop
end if
rs.close
%>
</select>　







中类：
<select name="Nclassid" >
<%rs.open "select * from shop_Nclass where anclassid="&selclass ,conn,1,1
if not(rs.eof and rs.bof) then
%>
<option selected value="<%=rs("nclassid")%>"><%=trim(rs("nclass"))%></option>
<%

rs.movenext

rs.movenext
do while not rs.eof%>
<option value="<%=rs("nclassid")%>"><%=trim(rs("nclass"))%></option>
<% rs.movenext
loop
end if
rs.close
set rs = nothing
%>
</select>