Sriram Sanka

create or replace function datediff( p_what in varchar2,
                                       p_d1   in date,
                                         p_d2   in date ) return number
    as
        l_result    number;
    begin
        select (p_d2-p_d1) *
               decode( upper(p_what),
                       'SS', 24*60*60, 'MI', 24*60, 'HH', 24, NULL )
        into l_result from dual;
 
       return l_result;
   end;
   /
   

WITH data
     AS (SELECT To_date(SYSDATE - 2, 'dd-mon-yyyy hh24:mi:ss') d1,
                To_date(SYSDATE, 'dd-mon-yyyy hh24:mi:ss')     d2
         FROM   dual)
SELECT Datediff('ss', d1, d2) AS seconds,
       Datediff('mi', d1, d2) AS minutes,
       Datediff('hh', d1, d2) hours
FROM   data 

SQL> WITH data
  2       AS (SELECT To_date(SYSDATE - 2, 'dd-mon-yyyy hh24:mi:ss') d1,
  3                  To_date(SYSDATE, 'dd-mon-yyyy hh24:mi:ss')     d2
  4           FROM   dual)
  5  SELECT Datediff('ss', d1, d2) AS seconds,
  6         Datediff('mi', d1, d2) AS minutes,
  7         Datediff('hh', d1, d2) hours
  8  FROM   data ;

   SECONDS    MINUTES      HOURS
---------- ---------- ----------
    172800       2880         48

SQL>