INSERT INTO `#__update_sites` (`name`, `type`, `location`, `enabled`) VALUES
('Joomla! Update Component Update Site', 'extension', 'https://update.joomla.org/core/extensions/com_joomlaupdate.xml', 1);

INSERT INTO `#__update_sites_extensions` (`update_site_id`, `extension_id`) VALUES
((SELECT `update_site_id` FROM `#__update_sites` WHERE `name` = 'Joomla! Update Component Update Site'), (SELECT `extension_id` FROM `#__extensions` WHERE `name` = 'com_joomlaupdate'));