Windows Search C++(MFC) OLE DB or ADO group search - mfc

Question

I have to run a group query like this :
GROUP ON System.ItemName OVER ( SELECT TOP 20 System.ItemName FROM SystemIndex )
But when I run it using C++ ADO Recordset I get an exception at Open ( when I search the SELECT TOP 20 System.ItemName FROM SystemIndex query it ruturns just fine).
so... how to perform a group search like that ?
ADO Code:
_ConnectionPtr connection = NULL;
hr = connection.CreateInstance(__uuidof(Connection));
_RecordsetPtr recordset = NULL;
hr = recordset.CreateInstance(__uuidof(Recordset));
hr = recordset->Open("GROUP ON System.Kind AGGREGATE COUNT() as 'Total' OVER ( SELECT TOP 20 System.ItemName, System.ItemUrl FROM SystemIndex )",
connection.GetInterfacePtr(), adOpenForwardOnly, adLockReadOnly, adCmdText);
After trying for a long time I decide to run into OLE DB directly , but it seems dificult to retreive the search data
OLE DB code:
CDataSource cDataSource;
hr = cDataSource.OpenFromInitializationString(connectionstring);
if (SUCCEEDED(hr))
{
CSession cSession;
if (SUCCEEDED(hr))
{
CCommand<CDynamicAccessor, CRowset> cCommand;
hr = cCommand.Open(cSession, L"GROUP ON System.ItemName OVER ( SELECT TOP 20 System.ItemName, System.Itemurl FROM SystemIndex )");
if (SUCCEEDED(hr))
{
for (hr = cCommand.MoveFirst(); S_OK == hr; hr = cCommand.MoveNext())
{
DBORDINAL columns= cCommand.GetColumnCount();
for (DBORDINAL i = 1; i <= columns; i++)
{
PCWSTR pszName = cCommand.GetColumnName(i);
//HOW TO GET DATA TO A sdt::string ?
}
}
cCommand.Close();
}
}
}