yearly salary budget rollup with 10g grouping function

thanks metaphysics for sharing this with me,
the function returns a value of 1 if the value of expr in the row is a null representing the set of all values.

SELECT
  DECODE(GROUPING(department_id), 1, '*', department_id) AS department,
  DECODE(GROUPING(job_id), 1, '*', job_id) AS job,
  COUNT(*) AS "Stuff", SUM(salary) * 12 AS "Yearly"
FROM hr.employees
GROUP BY ROLLUP (department_id, job_id)

Id	_Operation	Name	Rows	Bytes	Cost (%CPU)	Time
0	_SELECT STATEMENT		107	1712	4 (25)	00:00:01
1	__SORT GROUP BY ROLLUP		107	1712	4 (25)	00:00:01
2	___TABLE ACCESS FULL	EMPLOYEES	107	1712	3 (0)	00:00:01

NULL	SA_REP	1	84000
NULL	*	1	84000
10	AD_ASST	1	52800
10	*	1	52800
20	MK_MAN	1	156000
20	MK_REP	1	72000
20	*	2	228000
30	PU_MAN	1	132000
30	PU_CLERK	5	166800
30	*	6	298800
40	HR_REP	1	78000
40	*	1	78000
50	ST_MAN	5	436800
50	SH_CLERK	20	771600
50	ST_CLERK	20	668400
50	*	45	1876800
60	IT_PROG	5	345600
60	*	5	345600
70	PR_REP	1	120000
70	*	1	120000
80	SA_MAN	5	732000
80	SA_REP	29	2922000
80	*	34	3654000
90	AD_VP	2	408000
90	AD_PRES	1	288000
90	*	3	696000
100	FI_MGR	1	144000
100	FI_ACCOUNT	5	475200
100	*	6	619200
110	AC_MGR	1	144000
110	AC_ACCOUNT	1	99600
110	*	2	243600
*	*	107	8296800