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www.diandiba.com测试数据库：test.mdb，你可以自己建一个。
表1：big_class
字段：big_class_id(自动编号)，big_class_name（文本）
表2：small_class
字段：small_class_id(自动编号)，small_class_name（文本），belongto_big_class(数字)
以下是程序清单，共1个文件，文件名：test.asp
<%
'option explicit
dim conn,connstr,db
db="test.mdb" '测试数据库
Set conn = Server.CreateObject("ADODB.Connection")
connstr="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & Server.MapPath(""&db&"")
conn.Open connstr
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>ASP+JavaScript+数据库 级联下拉菜单</title>
<style>
table{border: #00215a 1px dashed;}
td{font-size:12px;}
input,select{
font-size:9pt;
border-style:solid;
border-width:1;
cursor:default;
color:#03326B;
background-color:#FFFFFF;
height:16px;
}
a:link,a:visited{color: #000000;text-decoration: none;}
a:hover {color: #ff0000;text-decoration: none;FILTER: glow(color=ffffff,strength=0) shadow(color=aaaaaa,direction:135); POSITION: relative; WIDTH: 100%;}
</style>
<script language="JavaScript">
function addbig(){
document.all.a.style.display="block";
document.all.b.style.display="none";
document.all.c.style.display="none";
}
function addsmall(){
document.all.b.style.display="block";
document.all.a.style.display="none";
document.all.c.style.display="none";
}
function viewmenu(){
document.all.a.style.display="none";
document.all.b.style.display="none";
document.all.c.style.display="block";
}
</script>
<%
'从小类表中取出数据
set rs=server.CreateObject("adodb.recordset")
sql="select * from small_class "
rs.open sql,conn,1,1
%>
<script language="JavaScript">
var num;
//定义数组
var calArray=new Array();
<%
dim j
j=0
do while not rs.eof
%>
//将小类表中的所有相关记录存到数组calArray的对应元素中。
calArray[<%=j%>]=new Array("<%=rs("small_class_id")%>","<%=rs("small_class_name")%>","<%=rs("belongto_big_class")%>");
<%
j=j+1
rs.movenext
loop
rs.close
set rs=nothing
%>
//给num赋值为记录总数
num=<%=j%>
function givevalue(myvalue){
/*当选择大类列表的值不为空时首先清空小类下拉列表的所有项目。不然小类列表中的项目会叠加的。
同时也是初始化 options 的值为0 */
document.form3.small_class_select.length = 0;
//循环写出请求的大类所对应的小类。
for (i=0;i < num; i++)
{
if (calArray[i][2] == myvalue)
{
document.form3.small_class_select.options[document.form3.small_class_select.length] = new Option(calArray[i][1], calArray[i][0],"","");
/*定义新的Option对象并赋值。options的索引值从0开始。new Option对象有4个属性，对应分别是：文本串、value、defaultSelect、selected。在这里只用了第一个和第二个。*/
}
}
}
</script>
<script language="JavaScript">
function chk1(){
if (form1.big_class_name.value=="")
{
alert("请输入大类名称！");
form1.big_class_name.focus();
return false;
}
}
function chk2(){
if (form2.small_class_name.value=="")
{
alert("请输入小类名称！");
form2.small_class_name.focus();
return false;
}
}
</script>
</head>
<body background="background.jpg">
<%
dim rs,sql,noclass
select case request("action")
case "addbigclass"
addbigclass
case "addsmallclass"
addsmallclass
end select
%>
<div align="center"></div>
<table width="60%" border="0" align="center" cellpadding="0" cellspacing="0">
<tr valign="middle">
<td height="48" colspan="3">
<div align="center"><font color="#999900"><b><font color="#FF0000">ASP</font>+<font color="#FF0000">JavaScript</font>+<font color="#FF0000">数据库</font>
级联下拉菜单</b></font></div></td>
</tr>
<tr>
<td width="22%" height="21" valign="bottom"><a href="#" onClick="addbig()">添加大类</a>
</td>
<td width="22%" valign="bottom"><a href="#" onClick="addsmall()">添加小类</a></td>
<td width="56%" valign="bottom"><a href="#" onClick="viewmenu()">预览效果</a></td>
</tr>
<tr>
<td height="33" colspan="3" valign="top">
<hr align="left" width="60%" size="1" color="#999900">
</td>
</tr>
<tr>
<td colspan="3" valign="top"> <div id="a" style="display:none">
<form name="form1" method="post" action="?action=addbigclass" onSubmit="return chk1()">
大类名称：
<input name="big_class_name" type="text" id="big_class_name" size="16">
<input type="submit" name="Submit" value=" 添 加 ">
</form>
</div>
<div id="b" style="display:none">
<form name="form2" method="post" action="?action=addsmallclass" onSubmit="return chk2()">
选择大类后添加小类：
<select name="addselect">
<%
set rs=server.CreateObject("adodb.recordset")
sql="big_class"
rs.open sql,conn,1,1
if rs.eof or rs.bof then
%>
<option selected>还没有添加大类</option>
<%
else
do while not rs.eof
%>
<option value="<%=rs("big_class_id")%>"><%=trim(rs("big_class_name"))%></option>
<%
rs.movenext
loop
end if
rs.close
set rs=nothing
%>
</select>
小类名称：
<input name="small_class_name" type="text" id="small_class_name" size="16">
<input type="submit" name="Submit2" value=" 添 加 ">
</form>
</div>
<div id="c" style="display:block">
<form name="form3" method="post" action="">
<select name="big_class_select" onChange="givevalue(document.form3.big_class_select.options[document.form3.big_class_select.selectedIndex].value)">
<%
dim firstid
set rs=server.CreateObject("adodb.recordset")
sql="select * from big_class order by big_class_id"
rs.open sql,conn,1,1
if rs.eof or rs.bof then
noclass=1
%>
<option selected>还没有添加大类</option>
<%
else
rs.movefirst
firstid=rs("big_class_id")
'在没有选择大类（页面刚载入）时要载入的大类。
%>
<option value="<%=rs("big_class_id")%>" selected><%=trim(rs("big_class_name"))%></option>
<%
rs.movenext
do while not rs.eof
%>
<option value="<%=rs("big_class_id")%>"><%=trim(rs("big_class_name"))%></option>
<%
rs.movenext
loop
end if
rs.close
set rs=nothing
%>
</select>
<select name="small_class_select">
<%if noclass=1 then%>
<option value="" selected>没有小类</option>
<%
else
'在没有选择大类（页面刚载入）时要载入的小类，要跟默认的大类对应。
set rs=server.CreateObject("adodb.recordset")
sql="select * from small_class where belongto_big_class="&firstid
rs.open sql,conn,1,1
if rs.eof or rs.bof then
%>
<option value="" selected>没有小类</option>
<%
else
do while not rs.eof
%>
<option value="<%=rs("small_class_id")%>"><%=trim(rs("small_class_name"))%></option>
<%
rs.movenext
loop
end if
rs.close
set rs=nothing
end if
%>
</select>
</form>
</div></td>
</tr>
</table>
<%
sub addbigclass()
set rs=server.CreateObject("adodb.recordset")
sql="select * from big_class where big_class_name='"&trim(request("big_class_name"))&"'"
rs.open sql,conn,1,3
if not(rs.eof and rs.bof) then
response.Write("<script>alert('该大类已经存在！');</script>")
else
rs.addnew
rs("big_class_name")=trim(request("big_class_name"))
rs.update
response.Write("<script>alert('大类添加成功！');self.location='test.asp?action=viewmenu';</script>")
end if
rs.close
set rs=nothing
end sub
sub addsmallclass()
set rs=server.CreateObject("adodb.recordset")
sql="select * from small_class where small_class_name='"&trim(request("small_class_name"))&"' and belongto_big_class="&request("addselect")
rs.open sql,conn,1,3
if not(rs.eof and rs.bof) then
response.Write("<script>alert('该小类已经存在！');</script>")
else
rs.addnew
rs("belongto_big_class")=request("addselect")
rs("small_class_name")=trim(request("small_class_name"))
rs.update
response.Write("<script>alert('小类添加成功！');self.location='test.asp?action=viewmenu';</script>")
end if
rs.close
set rs=nothing
end sub
conn.close
set conn=nothing
%>
</body>
</html>