CREATE TABLE Apartments (room_count INTEGER, apt_id VARCHAR(255)); CREATE TABLE Apartment_Facilities (apt_id VARCHAR(255), facility_code VARCHAR(255))
Show the total number of rooms of all apartments with facility code "Gym".
    
SQL: SELECT SUM(T2.room_count) FROM Apartment_Facilities AS T1 JOIN Apartments AS T2 ON T1.apt_id = T2.apt_id WHERE T1.facility_code = "Gym"