【SQL分页有关问题】点击上一页的时候查询不对

 string strsql = "select top "                           + NUMCount + " * from tb_Student where  ID not in ( select top "                           + number + " ID from tb_Student where fengcai=" + num + "  order by ID desc )and fengcai=" + num + " and email='" + shengfen + "' order by ID desc";