CREATE TABLE table_name_56 (rank NUMBER, code__iata_icao_ VARCHAR2)

What is the highest rank for the airport with a code of HKG/VHHH?
SELECT MAX(rank) FROM table_name_56 WHERE code__iata_icao_ = "hkg/vhhh"
SELECT MAX("rank") FROM "table_name_56" WHERE "code__iata_icao_" = "hkg/vhhh"