Show the total number of rooms of the apartments in the building with short name "Columbus Square".
SELECT sum(T2.room_count) FROM Apartment_Buildings AS T1 JOIN Apartments AS T2 ON T1.building_id  =  T2.building_id WHERE T1.building_short_name  =  "Columbus Square"
total number of rooms = SUM(room_count); apartments in the building with short name \"Columbus Square\" refers to a JOIN condition between Apartment_Buildings and Apartments tables on building_id and filtering with building_short_name = \"Columbus Square\";