17th from sql basic exam

SELECT t.Id,
        CASE WHEN ac.MiddleName IS NULL THEN  ac.FirstName + ' '+ ac.LastName ELSE  ac.FirstName + ' '+ ac.MiddleName+' '+ ac.LastName
        END
         AS 'Full Name',c.[Name] AS 'From',htl.[TO],
        CASE WHEN t.CancelDate IS NOT  NULL THEN  'Canceled' ELSE  CONCAT(CAST( DATEDIFF(DAY,t.ArrivalDate,t.ReturnDate)AS VARCHAR),' ','days')
        END
    AS 'Duration' FROM Trips AS t

JOIN AccountsTrips AS act ON t.Id=act.TripId
RIGHT JOIN Accounts AS ac ON act.AccountId=ac.Id
JOIN Cities AS c   ON ac.CityId=c.Id
JOIN Rooms AS r ON t.RoomId=r.Id
JOIN (SELECT c.Id, h.Id AS 'HotelID',c.Name AS 'To' FROM Hotels AS h
JOIN Cities AS c ON h.CityId=c.Id
GROUP BY c.Id,h.Id,c.Name) AS htl ON r.HotelId=htl.HotelID
ORDER BY [FULL Name],t.Id