CREATE TABLE documents (document_name VARCHAR, document_type_code VARCHAR, document_structure_code VARCHAR)

Find the list of documents that are both in the most three popular type and have the most three popular structure.
SELECT document_name FROM documents GROUP BY document_type_code ORDER BY COUNT(*) DESC LIMIT 3 INTERSECT SELECT document_name FROM documents GROUP BY document_structure_code ORDER BY COUNT(*) DESC LIMIT 3
SELECT "document_name" FROM "documents" GROUP BY "document_type_code" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 3 INTERSECT SELECT "document_name" FROM "documents" GROUP BY "document_structure_code" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 3