Oracle 18c

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
CREATE TABLE employees (employee_id, department_id) AS
SELECT 1, 1 FROM DUAL UNION ALL
SELECT 2, 1 FROM DUAL UNION ALL
SELECT 3, 1 FROM DUAL UNION ALL
SELECT 4, 2 FROM DUAL UNION ALL
SELECT 5, 2 FROM DUAL UNION ALL
SELECT 6, 2 FROM DUAL;
6 rows affected

DECLARE
  cursor emp_cursor(v_dept_id number) IS
    SELECT * FROM employees
    WHERE department_id = v_dept_id
    OR    v_dept_id = -1;
BEGIN 
  FOR emp_record IN emp_cursor(-1) LOOP
    dbms_output.put_line(' id = ' || emp_record.employee_id);
  END LOOP;
END;
/
1 rows affected

dbms_output:
 id = 1
 id = 2
 id = 3
 id = 4
 id = 5
 id = 6