防止反复评价的方法

<%
' 某文章号的状态判断是否为空?是,则更新记录,并改变状态;否,则提示,并不做处理。
if session(request("ID"))="" then
Set cmd1 = Server.CreateObject ("ADODB.Command")
cmd1.ActiveConnection = MM_conn_STRING
cmd1.CommandText = "UPDATE content SET zs=zs+1 WHERE ID="&request("ID")
cmd1.CommandType = 1
cmd1.CommandTimeout = 0
cmd1.Prepared = true
cmd1.Execute()
response.Write "<script>alert('恭喜您送钻石，欢迎再来');location.href('show.asp?ID="&request("ID")&"&bid="&request("bid")&"&sid="&request("sid")&"');</script>"
session(request("ID"))="ok"
else
response.Write "<script>alert('你已投过了!');location.href('show.asp?ID="&request("ID")&"&bid="&request("bid")&"&sid="&request("sid")&"');</script>"
end if
%>