关于时间

 sql = "SELECT SUM(Login) AS Num1, Media FROM Media_Login where  DATEDIFF(day, '" + Request["btime"].ToString() + "', logtime) >=0 and  DATEDIFF(day, logtime, '" + Request["etime"].ToString()
+ "') >=0  and gameid=" + game_name.SelectedValue + " GROUP BY Media  ";