Expression::concat

public function concat()
{
	$connection = \Bitrix\Main\Application::getConnection();
	$helper = $connection->getSqlHelper();
	$columns = func_get_args();
	$alias = static::getTmpName('CONCAT');

	// get ... format as well as single array
	if (count($columns) == 1 && is_array($columns[0]))
	{
		$columns = $columns[0];
	}

	$holders = array_fill(0, count($columns), '%s');
	$expr = call_user_func_array([$helper, 'getConcatFunction'], $holders);

	return new ExpressionField($alias, $expr, $columns);
}