Administrace komentářů

Díky za radu, pomohlo to. Bohužel pokud je uživatel někde na u konce tabulky, ten select dlouho trvá. Nakonec jsem to vyřešil jinak.
Mé řešení:

procedure TfrmMain.DBGrid1KeyDown(Sender: TObject; var Key: Word;
  Shift: TShiftState);
var
  id : Integer;
  f1 : TDateTime;
  f2 : String;
  f3 : Integer;
begin
  if (key = VK_END) and (Shift = [ssCtrl]) then
  begin
    if cDB_LIMIT > DbRecCount then
      DbOffset := 0
    else
      DbOffset := DbRecCount - cDB_LIMIT;
    try
      Q.DisableControls;
      trQ.Rollback;
      Q.SQL.Text := 'select * from cqrlog_main order by qsodate DESC, time_on DESC LIMIT '+IntToStr(cDB_LIMIT)+' OFFSET '+IntToStr(DbOffset);
      trQ.StartTransaction;
      Q.Open;
      Q.First
    finally
      Q.EnableControls
    end
  end;
  if (key = VK_HOME) and (Shift = [ssCtrl]) then
  begin
    try
      Q.DisableControls;
      trQ.Rollback;
      Q.SQL.Text := 'select * from cqrlog_main order by qsodate DESC, time_on DESC LIMIT '+IntToStr(cDB_LIMIT);
      trQ.StartTransaction;
      Q.Open
    finally
      Q.EnableControls
    end
  end;
  if ((key = VK_UP) or (key = 33)) and Q.BOF then
  begin
    try
      Q.DisableControls;
      id := Q.Fields[0].AsInteger;
      f2 := Q.Fields[2].AsString;
      f1 := Q.Fields[1].AsDateTime;
      Q1.SQL.Text := 'select id_cqrlog_main from cqrlog_main order by qsodate DESC, time_on DESC LIMIT 1';
      trQ1.StartTransaction;
      Q1.Open;
      f3 := Q1.Fields[0].AsInteger;
      trQ1.Rollback;
      Q1.Close;
      if f3=id then //we are on the begining of dataset
        exit;
      Q.Close;
      Q.SQL.Text := 'select * from (select * from cqrlog_main where (qsodate = '+QuotedStr(DateToStr(f1))+
                    'and time_on >= '+QuotedStr(f2)+') or qsodate > '+QuotedStr(DateToStr(f1))+
                    ' order by qsodate, time_on LIMIT '+IntToStr(cDB_LIMIT)+') as foo order by qsodate DESC,time_on DESC';
      trQ.Rollback;
      trQ.StartTransaction;
      Q.Open;
      Q.Last
    finally
      Q.EnableControls
    end
  end;

  if ((key = VK_DOWN) or (key = 34)) and Q.EOF then
  begin
    try
      Q.DisableControls;
      id := Q.Fields[0].AsInteger;
      f2 := Q.Fields[2].AsString;
      f1 := Q.Fields[1].AsDateTime;

      Q1.SQL.Text := 'select id_cqrlog_main from cqrlog_main order by qsodate,time_on LIMIT 1 OFFSET 0';
      trQ1.StartTransaction;
      Q1.Open;
      f3 := Q1.Fields[0].AsInteger;
      Q1.Close;
      trQ1.Rollback;
      if f3=id then //we are on the end of dataset
        exit;
      Q.Close;
      Q.SQL.Text := 'select count(*) from cqrlog_main where (qsodate = '+QuotedStr(DateToStr(f1))+
                    'and time_on <= '+QuotedStr(f2)+') or qsodate < '+QuotedStr(DateToStr(f1))+
                    ' order by qsodate DESC, time_on DESC LIMIT '+IntToStr(cDB_LIMIT);
      Q.Open;
      if Q.Fields[0].AsInteger < cDB_LIMIT then
      begin
        Q.Close;
        Q.SQL.Text := 'select * from (select * from cqrlog_main order by qsodate, time_on LIMIT '+
                       IntToStr(cDB_LIMIT)+') as foo order by qsodate DESC,time_on DESC';
       Q.Open;
       Q.Locate('id_cqrlog_main',id,[])
      end
      else begin
        Q.Close;
        Q.SQL.Text := 'select * from cqrlog_main where (qsodate = '+QuotedStr(DateToStr(f1))+
                      'and time_on <= '+QuotedStr(f2)+') or qsodate < '+QuotedStr(DateToStr(f1))+
                      ' order by qsodate DESC, time_on DESC LIMIT '+IntToStr(cDB_LIMIT);
        Q.Open;
        Q.Locate('id_cqrlog_main',id,[])
      end
    finally
      Q.EnableControls
    end
  end