Wrong Code

I'm Trying this code to switch the user group , so this code select users with groups only if the user doesn't have a group or does'nt exist redirect it to another page
Her is my code please check it
Code:

sql="select * from users,groups where users.user_id='"&id2&"' and users.group_id=groups.g_group_id"
set rs=conn.Execute(sql)
if rs.eof or rs("group_id")=null then
Response.Redirect("switch.asp?id="&session("session_id")&"&page=management")
else
dim group
group=rs("group_id")

end if
and It gives me this error message
Error Type:
(0x80020009)
Exception occurred.