select
24*60*60*floor(date-date1)+
60*60*(TRUNC(A*24)-TRUNC(b*24))+
60*(TRUNC(A*24*60-60*TRUNC(A*24))-TRUNC(B*24*60-60*TRUNC(B*24)))+
(TRUNC(A*24*60*60-60*TRUNC(A*24*60))-TRUNC(A*24*60*60-60*TRUNC(A*24*60)))
from
(
select
date-trunc(date) A,date1-trunc(date1) B
from dual
)