急！delphi怎样处理数据库输入重复数据问题？

Question

急！delphi怎样处理数据库输入重复数据问题？

Answer 1

不行，用ADOTable 输入Access 不想出现相同纪录

Answer 2

在adotable的beforepost中写代码判断数据库中是否已经存在相同的记录，如果存在就提示用户，这样可以吗

Answer 3

在Query的OnBeforePost事件来判断，如
procedure TForm1.QyBeforePost(DataSet: TDataSet);
var i : integer;
begin
  with TmpQy do
  begin
    close;
    sql.Clear;
    SQL.Text := 'select * from aTable where
CodeNo='+''''+Table.FieldByName('ID').AsString+'''';
    open;
    i := RecordCount;
    Close;
    if i> 0 then
    begin
      Application.MessageBox('对不起，编码重复，请您重新输入。','提示');
      Abort;
    end;
  end;
end;
ADO: 
通过ButtonClick事件保存！
 begin
        mysql3:='select id from table where xh=''';
        mysql4:='''';
        ADOQuery3.SQl.Clear;
        ADOQuery3.Close;
        ADOQuery3.SQL.Add(mysql3+Edit1.Text+mysql4);
        ADOQuery3.Open;
                If not ADOQuery3.eof then
                begin
                showMessage('对不起'+Edit1.Text+'已存在，请重新输入!');
                Edit1.Text:='';
                end
                else
                begin
                ADOQuery3.Close;
                ADOTable1.Insert;
                ADOTable1['a1']:=Edit6.Text;
                ADOTable1['a2']:=Edit1.Text;
                ADOTable1['a3']:=Edit5.Text;
                ADOTable1['a4']:=Edit3.Text;
                ADOTable1['a5']:=Edit4.Text;
                ADOTable1['a6']:=Edit2.Text;
                ADOTable1['a7']:=Combobox1.Text;
                ADOTable1.Post;
                end
        end