是否可以找到CustomADODataSet将要滚动到的记录？

Question

I want to make two datasets, DS1 and DS2 , scroll simultaneously. These are actually results of queries on same table with different fields. First one is used for UI and has lots of calculated fields and second one is a simple editable dataset with few data fields. I want both datasets have active record with same ID . So, since I assume that DS1 record set is a subset of DS2 's, I just call DS2.Locate in DS2.AfterScroll . But my assumption can be technically violated (due to bad configuration). So I want to abort the scrolling process of DS1 when there's no corresponding record in DS2 . By scrolling process I mean changing active record of DS1 and firing DS1.AfterScroll .

Answer 1

The following should do what I understand you to mean, in other words the active record of DS2 tracks the active record of DS1. The example uses the authors table of the MS demo pubs database for Sql Server. Ideally, it would have an integer primary key ID column, but unfortunately authors doesn't.

TForm1 = class(TForm)
  ADOConnection1: TADOConnection;
  DS1: TADOQuery;
  DS2: TADOQuery;
  DataSource1: TDataSource;
  DataSource2: TDataSource;
  DBGrid1: TDBGrid;
  DBGrid2: TDBGrid;
  DBNavigator1: TDBNavigator;
  DBNavigator2: TDBNavigator;
  procedure DS1AfterScroll(DataSet: TDataSet);
  procedure FormCreate(Sender: TObject);
protected
  DS2au_id,
  DS2au_lname,
  DS2au_fname : TStringField;
public
end;

[...]

procedure TForm1.DS1AfterScroll(DataSet: TDataSet);
begin
  if DS2.Active then
    DS2.Locate('au_ID', DS1.FieldByName('au_ID').AsString, []);
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  DS1.SQL.Text := 'select * from authors';
  DS2.SQL.Text := 'select au_id, au_name, au_fname from authors';
  DS1.Open;

  DS2au_id := TStringField.Create(Self);
  DS2au_id.FieldName := 'au_ID';
  DS2au_id.Size := 11;
  DS2au_id.DataSet := DS2;


  DS2au_lname := TStringField.Create(Self);
  DS2au_lname.FieldName := 'au_lname';
  DS2au_lname.Size := 40;
  DS2au_lname.DataSet := DS2;


  DS2au_lname := TStringField.Create(Self);
  DS2au_lname.FieldName := 'au_fname';
  DS2au_lname.Size := 20;
  DS2au_lname.DataSet := DS2;

  DS2.Recordset := DS1.Recordset;
end;

If you do it this way, the answer to your q

Is it possible to find the record that CustomADODataSet is about to scroll to?

is that you don't need to.