select idapartment, sum(sut) sut from 
    (select idaparatment, ceil((dateto - datefrom) / 10e5) sut from reservations) t 
    group by 1

create table sprav_sut
( 
    ss_id int auto_increment
    , df datetime
    , dt datetime
    , primary key(ss_id, df, dt)

);

insert into sprav_sut (df, dt) values 
('14.09.06 00:00', '14.09.06 23:59:59')
, ('14.09.07 00:00:00', '14.09.07 23:59:59')
, ('14.09.08 00:00:00', '14.09.08 23:59:59')
...
, ('50.12.31 00:00:00', '50.12.31 23:59:59')

select idapartment, count(ss_id) as sut from 
(
    select ss_id, idapartment 
        from reservations d join sprav_sut s 
            on (d.df <= s.df and d.dt >= s.dt) 

        group by 1

) t 

group by 1

create table bree (i int auto_increment, primary key(i));
insert into bree values (), (), (), (), (), (), (), (), (), (), (), (), (), ();


select idapartment, count(cnt) as cnt from
(
    select distinct stayday as cnt, idapartment from
    (
        select 
        idapartment
        , if 
        (
            unix_timestamp(date(d.datefrom))
            - unix_timestamp(date(d.dateto)) 
            - 60 * 60 * 24 * (s.i - 1)) 

                >= 0, 

            date(d.datefrom + 10e5 * (s.i - 1))
            , 0

        ) stayday

        from reservations d, bree s 
        
    ) t1

    where stayday > 0

) t2

group by 1

select room_id, count(ss_id) as sut from 
(
    select ss_id, room_id 
	from reservations d join sprav_sut s 
	on ((s.df between d.reservation_start and d.reservation_end or s.dt between d.reservation_start and d.reservation_end) or (s.df < d.reservation_end and s.dt > d.reservation_start))  
        group by s.ss_id
) t 
group by room_id

id    idapartment    datefrom           dateto
1     5              07.09.14 10:00     07.09.14 19:00