select user_id,g.room_id,room_type,
    (day(checkout_time)-day(checkin_time)) days
from guestroom_tb g join checkin_tb c on g.room_id = c.room_id 
where (day(checkout_time)-day(checkin_time))=1 
       and (hour(checkout_time)-hour(checkin_time))>0 
       or  (day(checkout_time)-day(checkin_time))>1 
       and mid(checkin_time,7,4) = '6-12'
order by days,g.room_id,c.user_id desc