client端的数据操作问题

我在对数据进行添加操作是，发现数据添加不进去。。我估计应该是在挑选数据时出了问题，那位大哥帮忙看看问题出在哪里。。谢谢。
begin
  if btnAppend.Caption='添加' then
  begin
   DBEdit1.SetFocus;
   btnAppend.Caption:='提交';
   btnModify.Caption:='取消';
   btnDelete.visible:=false;
   btnSearch.visible:=false;
   btnCancel.Visible:=false;
  end
  else
  begin
  if (Trim(DBEdit1.Text)='') then
     begin
       showMessage('工号不能为空');
       exit;
     end;
     if (Trim(DBEdit2.Text)='') then
     begin
       showMessage('姓名不能为空');
       exit;
     end;
     with client_data_fm.cd_Stano do
         begin
           close;
           commandtext:='select * from Stano where Sid='+''''+DBEdit1.Text+'''';
           open;
         end;
           if client_data_fm.cd_Stano.Fields[1].AsString<>'' then
           begin
           showMessage('此工号已存在');
           exit;
           end
           else
           begin
            client_data_fm.cd_stano.Append;
  
           end;
            client_data_fm.cd_stano.ApplyUpdates(-1);
           end;
             DBEdit1.Text:='';
             DBEdit2.Text:='';
             DBEdit3.Text:='';
             DBEdit4.Text:='';
             DBEdit6.Text:='';
             DBEdit7.Text:='';
             DBEdit8.Text:='';
             DBEdit9.Text:='';
             DBEdit10.Text:='';
             DBEdit11.Text:='';
             DBEdit12.Text:='';
             DBEdit13.Text:='';
             DBEdit14.Text:='';
             DBEdit15.Text:='';
             DBEdit16.Text:='';
             DBComboBox1.Text:='';
             DBComboBox2.Text:='';
             DBComboBox3.Text:='';
             DBComboBox4.Text:='';
             client_data_fm.cd_stano.Append;
end;