CREATE TABLE Reservations (Room VARCHAR(255)); CREATE TABLE Rooms (decor VARCHAR(255), RoomId VARCHAR(255))
What kind of decor has the least number of reservations?
    
SQL: SELECT T2.decor FROM Reservations AS T1 JOIN Rooms AS T2 ON T1.Room = T2.RoomId GROUP BY T2.decor ORDER BY COUNT(T2.decor) LIMIT 1