What are the names of documents that do not have any sections?
SELECT document_name FROM documents WHERE document_code NOT IN (SELECT document_code FROM document_sections)
SELECT document_name FROM documents WHERE document_code NOT IN (SELECT document_code FROM document_sections)
[{'document_name': 'Learning Database'}, {'document_name': 'How to cook pasta'}, {'document_name': 'Humanity: a fact'}, {'document_name': 'Life about Claude Monet'}]