SELECT
 menu.*,
 news.seo_filename AS news_seo_filename,
 articles.seo_filename AS article_seo_filename,
 subpages.seo_filename AS subpage_seo_filename
FROM menu
LEFT OUTER JOIN news ON menu.link = news.id
LEFT OUTER JOIN articles ON menu.link = articles.id
LEFT OUTER JOIN subpages ON menu.link = subpages.id
ORDER BY lft