Programs Knowledge

create or replace function GetWeekOfYear(dt Timestamp) 
 return number
is
weekOfYear number; 
begin
  select ceil
  (
     (
        to_number(to_char(dt, 'DDD')) -
        (8 - to_char(trunc(dt, 'YYYY'), 'D'))
     ) / 7 + 1
  ) into weekOfYear from dual;       
 
  return weekOfYear;
end GetWeekOfYear;