with  
function  
  getrand(pval in number) return number is   --- many more times we get a result set (we aren't even using the parameter)  
--  getrand                 return number is   --- many fewer times we get a result set (yes, keep trying, it does happen)  
begin  
  return round(dbms_random.value(0,20));  
end;  
  
my_rnd as  
  (  
    select object_id, getrand(object_id) getrnd from all_objects  
--    select object_id, getrand            getrnd from all_objects  
  )  
  
select * from my_rnd where getrnd = 10;