tree views in BCB

void __fastcall TForm1::Button1Click(TObject *Sender)
{
	BuildNodes(NULL, 0);
}
//---------------------------------------------------------------------------
void TForm1::BuildNodes(TTreeNode *parent, int parent_id)
{
	TQuery *qry;
	char sql[1024];
	AnsiString name;
	int id;
	TTreeNode *Node;

	qry = new TQuery(this);
	qry->DatabaseName = "Database1";
	qry->SQL->Clear();
	sprintf(sql, "SELECT id, name FROM table WHERE parent_id = %d", parent_id);
	qry->SQL->Add(sql);
	qry->Open();
	// Might need to uncomment the next two lines
	// for certain DB engines, that lock tables when the result 
	// set is cached on the server end, until the client 
	// fetches all the results.
	// qry->Last();
	// qry->First();
	while (!qry->Eof) {
		id = qry->FieldByName("id")->AsInteger;
		name = qry->FieldByName("name")->AsString;
		Node = TreeView1->Items->AddChild(parent, name);
		// Now recurse into function to build children
		BuildNodes(Node, id);
                                
		// Get the next sibling
		qry->Next();
	}
	qry->Close();
	delete qry;
}