with t(pos_id, emp_id, emp_position, fd, td) as (select 1, 1,	'уборщик', date'2017-01-01', date'2017-01-10'
from dual union all select 75, 1, 'ст.уборщик', date'2017-01-11', date'2017-01-25'
from dual union all select 8654, 1, 'гл.уборщик', date'2017-01-22', date'2017-02-01'
from dual
)
, solution1 as (
  select t1.pos_id, t1.emp_position, t1.fd, t1.td 
    from t t1, t t2
   where t1.emp_id = t2.emp_id
     and t1.fd < t2.td
     and t1.td > t2.fd
     and t1.pos_id <> t2.pos_id
)
, solution2 as (
  select pos_id, emp_position, fd, td, i_flag 
    from (
    select pos_id, emp_position, fd, td
         , case when fd < max(td) over(partition by emp_id order by fd rows between unbounded preceding and 1 preceding) then 'intersect with prior'
                when td > min(fd) over(partition by emp_id order by td rows between 1 following and unbounded following) then 'intersect with following'
            end i_flag
    from t
  ) where i_flag is not null
)
select * from 
solution1
--solution2

  9  ,lag(td,1,fd-1) over (partition by emp_id order by fd /* td*/) la