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	QString sSql = QString("SELECT id, name FROM elements WHERE parent_id IS NULL OR parent_id=0 ORDER BY name ASC");
	QSqlQuery parentsQuery;
	if(!parentsQuery.exec(sSql))
		return;

	while(parentsQuery.next())
	{
		int parentId = parentsQuery.value(0).toInt();
		QString parentName = parentsQuery.value(1).toString();

		QTreeWidgetItem* parentItem = new QTreeWidgetItem(someTreeWidget, QStringList(parentName));
		parentItem->setData(0, Qt::UserRole + 1, parentId);
		someTreeWidget->addTopLevelItem(parentItem); // вероятно, можно удалить, т.к. в теории QTreeWidgetItem(someTreeWidget, ...) сделает ноду топовой
		{
			sSql = QString("SELECT id, name FROM elements WHERE parent_id=%1 ORDER BY name ASC").arg(parentId);
			QSqlQuery childrenQuery;
			if(childrenQuery.exec(sSql))
			{
				while(childrenQuery.next())
				{
					int childId = childrenQuery.value(0).toInt();
					QString childName = childrenQuery.value(1).toString();

					QTreeWidgetItem* childItem = new QTreeWidgetItem(parentItem, QStringList(childName));
					childItem->setData(0, Qt::UserRole + 1, childId);
				}
			}
		}
	}

void MyDialog::BuildTree(){

QSqlQuery cities, districts;
bool ok=cities.exec("SELECT cityname FROM cities ORDER BY cityname;");
if (!ok) {
		QMessageBox::warning(this, tr("SuperProga"), cities.lastError().text());
		return;
	}

model=new QStandardItemModel(this);
QStandardItem *parentItem = model->invisibleRootItem();

	while(cities.next()){
		QStandardItem *item = new QStandardItem(QString("%0").arg(cities.value(0).toString()));
		parentItem->appendRow(item);
	    
		  districts.prepare("SELECT disname FROM districts WHERE CityID=(SELECT ID FROM cities WHERE cityname LIKE :city) ORDER BY disname;");
		  districts.bindValue(":city", cities.value(0).toString());
		  bool disok=districts.exec();
		  if (!disok) {
			  QMessageBox::warning(this, tr("SuperProga "), districts.lastError().text());
			return;
			}
		  while(districts.next()){
			QStandardItem *itemchild = new QStandardItem(QString("%0").arg(districts.value(0).toString()));
			item->appendRow(itemchild);
					
	  }
		  
		
		
	}
	model->setHeaderData(0, Qt::Horizontal, tr("Cities"));	
	treeView->setModel(model);
	treeView->setAlternatingRowColors(true);
	treeView->setEditTriggers(QAbstractItemView::NoEditTriggers);
}

parentItem->appendRow(item);

parentItem = item;