[求助] ACCESS数据库里数字与文本的关系求助

一个匪夷所思的问题
若把数据据库中danganbianhao字段设置成数字型这个检测是否重复的代码就一致提示无重复但是的确有重复的
只要把这个字段设置成文本格式立马就能检测到重复这是为什么啊
求大神指点并更正。谢谢
代码如下：

<%
Response.Buffer = True
Response.ExpiresAbsolute = Now() - 1
Response.Expires = 0
Response.CacheControl = "no-cache"
Response.AddHeader "Pragma", "No-Cache"on error resume next
db_path = "data/FireWeb_Right.mdb"
Set conn= Server.CreateObject("ADODB.Connection")
connstr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source="&Server.MapPath(db_path)
conn.Open connstrFunction CloseDatabase
Conn.close
Set conn = Nothing
End Functionnum=request.querystring("num")
Set rs = Server.CreateObject ("ADODB.Recordset")
sql = "Select * from list where danganbianhao='"&num&"'"
rs.Open sql,conn,1,1
if rs.eof and rs.bof then
response.write("没有重复")
else
response.write("　发现重复")
end if
rs.close
set rs=nothing
call CloseDatabase
%>