sql="select * from users where users_name='" & username &"'"
response.Write(sql)
Set conn=Server.CreateObject("ADODB.Connection")'准备建立数据库连接
Set rs=Server.CreateObject("ADODB.Recordset")'准备建立记录集
conn.ConnectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source="&Server.MapPath(db)'MAPPATH获取本机绝对路径
conn.open'数据库连接
rs.ActiveConnection=conn '设置rs的活动属性
rs.CursorType=2 '游标类型
rs.LockType=2 '锁定类型
rs.Open sql '记录集打开并执行SQL语句
if rs.RecordCount>0 Then '发现重复用户名提示并返回注册页面
  response.write"<script>alert('该用户名已经被注册，请重新输入')</script>"
  response.write"<script>history.go(-1)</script>"
  response.End()
end if
sql="insert into users(users_name,users_pass,users_webname,users_mail) values('"& username & "','"& userpass & "','"& userwebname & "','"& usermail & "')"
response.Write(sql)
conn.Execute sql
conn.Close
Set conn= Nothing