CREATE TABLE has_amenity (dorm_name VARCHAR2, dormid VARCHAR2)
CREATE TABLE dorm (dorm_name VARCHAR2, dormid VARCHAR2)

Find the name of dorms that do not have any amenity
SELECT dorm_name FROM dorm WHERE NOT dormid IN (SELECT dormid FROM has_amenity)
SELECT "dorm_name" FROM "dorm" WHERE NOT "dormid" IN (SELECT "dormid" FROM "has_amenity")