core-bundle/src/Resources/contao/library/Contao/Database.php
public function getUuid()
	{
		static $ids;

		if (empty($ids))
		{
			$statement = $this->resConnection->executeQuery(implode(' UNION ALL ', array_fill(0, 10, "SELECT UNHEX(REPLACE(UUID(), '-', '')) AS uuid")));
			$ids = $statement->fetchAll(\PDO::FETCH_COLUMN);
		}

		return array_pop($ids);
	}
public function getUuid()
	{
		static $ids;

		if (empty($ids))
		{
			$statement = $this->resConnection->executeQuery(implode(' UNION ALL ', array_fill(0, 10, "SELECT UNHEX(REPLACE(UUID(), '-', '')) AS uuid")));
			$ids = $statement->fetchAll(\PDO::FETCH_COLUMN);
		}

		return array_pop($ids);
	}
Return a universal unique identifier

@return string The UUID string