If you have deeply nested XML documents (or json, html, sql) with recursive nodes (node 'folder' in node 'folder' in node 'folder') of a mixed complex type without an XSD/DTD schema you can use the tool eXtractorONE (eXtractor.ONE). No programming needed, no Xquery, no XSLT, nearly zero configuration. No limit on size. Just point to the folder with XML documents, select your target database and run it.