CREATE TABLE documents (document_structure_code VARCHAR2)
CREATE TABLE document_structures (document_structure_description VARCHAR2, document_structure_code VARCHAR2)

What is the structure of the document with the least number of accesses?
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
SELECT "t2"."document_structure_description" FROM "documents" "t1" JOIN "document_structures" "t2" ON "t1"."document_structure_code" = "t2"."document_structure_code" GROUP BY "t1"."document_structure_code" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY