create or replace function get_student
(p_schema in varchar2, p_tab in varchar2) return varchar2 as
e_ret varchar2(2000);
counter number;
begin
  select count(*) into counter from dba_role_privs;
end;
/

select any dictionary

  1  create or replace function get_student
  2  return number as
  3  counter number;
  4  begin
  5    select count(*) into counter from dba_role_privs;
  6    return counter;
  7*   end;
scott@chum > /

Function created.

scott@chum > select get_student from dual;

GET_STUDENT
-----------
	151

scott@chum > select count(*) from dba_role_privs;

  COUNT(*)
----------
       151