Table schema:
CREATE TABLE document_structures (document_structure_description VARCHAR, document_structure_code VARCHAR); CREATE TABLE documents (document_structure_code VARCHAR)

Question: What is the structure of the document with the least number of accesses?
SQL: SELECT t2.document_structure_description FROM documents AS t1 JOIN document_structures AS t2 ON t1.document_structure_code = t2.document_structure_code GROUP BY t1.document_structure_code ORDER BY COUNT(*) DESC LIMIT 1