TÉMA:

// cell all clear checked
procedure TForm.DBGridCellClear;
begin
  // check all
  SQLQuery.Close;
  SQLQuery.Open;
  SQLQuery.First;
  while not SQLQuery.EOF do begin
        RecList.CurrentRowSelected := False;
        SQLQuery.Next;
  end; // while
end;

  Dataset.First;
  while not ( Dataset.EOF ) do begin
    DBGridCellClick( DBGrid.Columns[0] );
    Dataset.Next;
  end;

  SQLQuery.First;
  while not SQLQuery.EOF do begin
        q:= SQLQuery.FieldByName('q').AsBoolean;
        if (  q ) then
           // checked the checkbox
           DBGridCellClick( DBGrid.Columns[0] );
        SQLQuery.Next;
  end; // while               

BooleanArray[2] := True;
DBGrid.Refresh;

procedure KonyvjelzozottRekordokKezelese;
var I:Integer;
begin
	DBGrid1.DataSource.Dataset.DisableControls; { DBGrid1 ne ugráljon amíg alkotunk }
	for I:=0 to DBGrid1.SelectedRows.Count-1 do begin
	 	DBGrid1.DataSource.Dataset.GotoBookmark(TBookmark(DBGrid1.SelectedRows[I]));
  		{ itt azt teszel a rekorddal amit akarsz }
	end;
	DBGrid1.DataSource.Dataset.EnableControls; { DBGrid1 újra követheti az adatforrás változásait }
end;

var BooleanArray: array of boolean
 
implementation
 
{$R *.lfm}
 
{ TForm1 }
 
procedure TForm1.FormCreate(Sender: TObject);
var  i: integer;
begin
  SQLQuery.Last;
  SetLength(BooleanArray, SQLQuery.RecordCount); // hogy pontos legyen a RecordCount értéke
  SQLQuery.First;
  for i := 0 to Length(BooleanArray) - 1 do BooleanArray[i] := False;
end;
 
procedure TForm1.DBGridCellClick(Column: TColumn);
begin
  if Column.Index = 0 then BooleanArray[DBGrid.DataSource.DataSet.RecNo] := not BooleanArray[DBGrid.DataSource.DataSet.RecNo];
end;
 
procedure TForm1.DBGridUserCheckboxState(Sender: TObject; Column: TColumn; var AState: TCheckboxState);
begin
  if BooleanArray[TDBGrid(Sender).DataSource.DataSet.RecNo] = True then AState := cbChecked else AState := cbUnChecked;
end;
 
procedure TForm1.FormDestroy(Sender: TObject);
begin
  SetLength(BooleanArray, 0);
end;

var x: boolean;// x: variant;
...
x := DBGrid.Columns[0].Field.Value;
...

  SQLQuery.First;
  while not SQLQuery.EOF do begin
    if ( DBGrid.SelectedRows.CurrentRowSelected )
       then
         ShowMessage( 'True' )
       else
         ShowMessage( 'False' );
    SQLQuery.Next;
  end; // for