with t as (
select to_date('02.03.2017 17:30:13','dd.mm.yyyy hh24:mi:ss') d1,
       to_date('23.02.2017 23:04:51','dd.mm.yyyy hh24:mi:ss') d2 from dual
)
,tt as (
select  
 --первый день
 case --з
  when d2<trunc(d2)+09/24 then 9*60 
  when d2>trunc(d2)+18/24 then 0 
  else (d2-trunc(d2))*24*60-9*60
  end d2
,
 --последний день
 case --з
  when d1<trunc(d1)+09/24 then 0
  when d1>trunc(d1)+18/24 then 9*60 
  else (d1-trunc(d1))*24*60-9*60
  end  d1
, --полные дни
((trunc(d1)-trunc(d2))-1)*9*60 d
from t
)
select (d+d1+d2) mi_all from tt

SQL> /

    MI_ALL
----------
3750,21667

, --полные дни
((trunc(d1)-trunc(d2))-1)*9*60 d
from t
) 

 with t as (
 select to_date('08.12.2017 17:00:00','dd.mm.yyyy hh24:mi:ss') d_from
       ,to_date('12.12.2017 09:20:00','dd.mm.yyyy hh24:mi:ss') d_to
 from dual
 )
 ,tt as (
 select
  --первый день
  case --з
   when d_from<trunc(d_from)+09/24 then 9*60
   when d_from>trunc(d_from)+18/24 then 0
   else ((trunc(d_from)+18/24) - d_from)*24*60
   end mi_from
 ,
 --последний день
  case --з
   when d_to<trunc(d_to)+09/24 then 0
   when d_to>trunc(d_to)+18/24 then 9*60 
   else (d_to-trunc(d_to))*24*60-9*60
   end  mi_to 
, 
--полные дни
 (select (sum(decode(mod(to_char(d_from+level,'j'),7),5,0,6,0,1))) *9*60 
 from t
 connect by d_from+level<d_to
 ) mi
 ,d_from
 ,d_to
 from t
 )
 select decode(trunc(d_from),trunc(d_to),(d_to-d_from)*24*60,mi+mi_from+mi_to) mi_all
--,mi_from,mi_to,mi  
from tt

SQL> /

    MI_ALL
----------
       620