▣ 집계형 함수

select avg(sal) as [평균] from emp
-- 평균
select avg(isnull(cmm.0)) as [커미션] from emp
--

select sum(sal)/count(sal) as [평균]from emp
-- 총합계 / 개수

select max(sal) as [최고급여] from emp
-- 최고값

select min(sal) as [최저급여] from emp
-- 최저값



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