SQL> create or replace package FooLib as
  2          empNo   number;
  3          function GetEmpSurname( empNo number default FooLib.empNo ) return varchar2;
  4  end;
  5  /

Package created.

SQL> 
SQL> create or replace package body FooLib as
  2  
  3          function GetEmpSurname( empNo number default FooLib.empNo ) return varchar2 is
  4                  surname         emp.ename%Type;
  5          begin
  6                  select
  7                          e.ename into surname
  8                  from    emp e
  9                  where   e.empno = GetEmpSurname.empNo;
 10  
 11                  return( surname );
 12          end;
 13  
 14  
 15  end;
 16  /

Package body created.

SQL> -- use call with parameter
SQL> exec dbms_output.put_line( FooLib.GetEmpSurname(7499) );
ALLEN

PL/SQL procedure successfully completed.

SQL> -- use call via static package variable
SQL> exec FooLib.empNo := 7654; dbms_output.put_line( FooLib.GetEmpSurname );
MARTIN

PL/SQL procedure successfully completed.

SQL> 

CREATE OR REPLACE PACKAGE update_planned_hrs
IS
      Planned_hours NUMBER(4);  
 
      PROCEDURE set_new_planned (p_emp_id IN NUMBER, p_project_id IN NUMBER, p_hours IN NUMBER);
       FUNCTION existing_planned (p_emp_id IN NUMBER, p_project_id IN NUMBER) RETURN NUMBER;
 
END update_planned_hrs;
/
 
CREATE OR REPLACE PACKAGE BODY update_planned_hrs
IS
 
PROCEDURE set_new_planned (p_emp_id IN NUMBER, p_project_id IN NUMBER, p_hours IN NUMBER)
IS
BEGIN
   UPDATE employee_on_activity ea
   SET ea.ea_planned_hours = p_hours
   WHERE
            ea.ea_emp_id = p_emp_id            
            AND ea.ea_proj_id = p_project_id;
 
EXCEPTION
          WHEN NO_DATA_FOUND THEN
           RAISE_APPLICATION_ERROR (-20100, 'No such employee or project');
 
END set_new_planned;
 
FUNCTION existing_planned (p_emp_id IN NUMBER, p_project_id IN NUMBER) RETURN NUMBER
 
IS
 
existing_hours NUMBER(4);
 
BEGIN
   SELECT ea.ea_planned_hours INTO existing_hours 
   FROM employee_on_activity ea
   WHERE
            ea.ea_emp_id = p_emp_id     
            AND ea.ea_proj_id = p_project_id; 
 
   RETURN (existing_hours);
 
   EXCEPTION
          WHEN NO_DATA_FOUND THEN
           RAISE_APPLICATION_ERROR (-20100, 'No such employee or project');
 
 
   END existing_planned;
 
END update_planned_hrs;