CREATE TABLE reservations (code DECIMAL, room TEXT, checkin TEXT, checkout TEXT, rate DECIMAL, lastname TEXT, firstname TEXT, adults DECIMAL, kids DECIMAL)
CREATE TABLE rooms (roomid TEXT, roomname TEXT, beds DECIMAL, bedtype TEXT, maxoccupancy DECIMAL, baseprice DECIMAL, decor TEXT)

How many rooms have not had any reservation yet?
SELECT COUNT(*) FROM rooms WHERE NOT roomid IN (SELECT DISTINCT room FROM reservations)
SELECT COUNT(*) FROM "rooms" WHERE NOT "roomid" IN (SELECT DISTINCT "room" FROM "reservations")