Advanced Oracle SQL: Windowing Clause

Question

I'm trying to learn subject mentioned topic but unable to understand it properly, I looked into google and read few articles but those are confusing so if someone send me some good and easy link for this clause  or tell me this clause in simple words then I really appreciate it. Thanks

Answer 1

I think Mr. DBMS_RANDOM.value(100000,999999) wants to understand what a Windowing Clause means more than "how do I write one?".
In that case, the only way to teach will be by example.
with number_generator as (
  select level as counter
  from dual
  connect by level<=20
select
  counter
,counter || ' + ' || nvl(lag(counter,1) over (order by counter),0) || ' = '
   as math_text
,sum( counter ) over (order by counter rows between 1 preceding and current row)
    as sum_of_last_2_rows
,sum( counter ) over (order by counter rows between unbounded preceding and current row)
    as running_total
,sum( counter ) over (order by counter rows between current row and unbounded following)
    as running_total_reverse_1
,sum( counter ) over (order by counter desc rows between unbounded preceding and current row)
    as running_total_reverse_2
,sum( counter ) over ( /* order by counter rows between unbounded preceding and unbounded following */  )
    as sum_all_rows
from number_generator
order by counter;