[Ildar-tsr]

Код:

procedure TForm1.DBComboBox1DropDown(Sender: TObject);
var
  i: integer;
  s: string;
begin
  i := 0;
  s:= '';
  while i < DBGrid1.DataSource.DataSet.RecordCount do
    begin
      if s <> DBGrid1.Fields[0].AsString then       
        begin
          DBGrid1.Columns[0].PickList.Add(DBGrid1.Fields[0].AsVariant);
          s:= DBGrid1.Fields[0].AsString;
        end;
      inc(i);
    end;
  DBComboBox1.Items.Assign(DBGrid1.Columns[0].PickList);
end;