[Assistant]

примерно так:

Код:

procedure TForm2.btn7Click(Sender: TObject);
var
  total: integer;
begin
  Query2.Close;
  Query2.SQL.Clear;
  Query2.SQL.Add('Select SUM(total) AS sum_total from MAINDIG.DBF where model LIKE ' + #39 + '%' + Edit2.Text + '%' + #39) ;
  Query2.Open;
  total := Query2.FieldByName('sum_total').AsInteger;
  Query2.Close;
end;