, count(department_id) headcount
from employees
group by rollup(department_id, job_id);
DEPARTMENT_ID JOB_ID HEADCOUNT
------------- ---------- ----------
SA_REP 0
0
10 AD_ASST 1
10 1
20 MK_MAN 1
20 MK_REP 1
20 2
30 PU_MAN 1
30 PU_CLERK 5
30 6
40 HR_REP 1
DEPARTMENT_ID JOB_ID HEADCOUNT
------------- ---------- ----------
40 1
50 ST_MAN 5
50 SH_CLERK 20
50 ST_CLERK 20
50 45
60 IT_PROG 5
60 5
70 PR_REP 1
70 1
80 SA_MAN 5
80 SA_REP 29
DEPARTMENT_ID JOB_ID HEADCOUNT
------------- ---------- ----------
80 34
90 AD_VP 2
90 AD_PRES 1
90 3
100 FI_MGR 1
100 FI_ACCOUNT 5
100 6
110 AC_MGR 1
110 AC_ACCOUNT 1
110 2
106