14일차 # 4-13 Grouping Sets

- 컬럼에 대해 임의의 그룹을 지음

    - ()

  - Union All 로 똑같은 결과를 얻을 수 있으나 보다 효율적임

select deptno, job, sum(sal) from emp

group by rollup(deptno, job);

  ↓↓

select deptno, job, sum(sal) from emp

group by deptno, job

union all

select deptno, to_char(null), sum(sal) from emp

group by deptno

union all

select to_number(null), to_char(null), sum(sal) from emp

group by ()

order by 1, 2;