[데이터 베이스]5.그룹핑 방법 예시

-- 3. 그룹핑 하기 
select avg(SAL), deptno
from emp
where deptno = 10
union all
select avg(SAL), deptno
from emp
where deptno = 20
union all
select avg(SAL), deptno
from emp
where deptno = 30;

select avg(SAL)
from emp
group by deptno;

-- 4. 그루핑 원리 실습하기

select avg(height), grade, substr(jumin, 1 , 2)
from student
group by grade, jumin;

select avg(height), grade
from student
group by grade;

-- 교수테이블에서 500만원 이상 버는 사람들과 그 미만인 사람들을 그룹으로 나누어, pay의 평균을 구하시오.
-- select avg(pay)
-- from professor
-- group by if pay > 500;

select job, deptno, avg(sal) 
from emp
group by job, deptno
having deptno != 10;

select avg(sal), deptno
from emp
group by deptno
having avg(sal) >2000;