SQL(Aggregate Fuctions-집계함수)

Aggregate Fuctions 집계함수
★ 집계함수는 Select or Group by 에서만 사용 가능!! ★

• 여러 칼럼 혹은 테이블 전체 칼럼으로부터 하나의 결과값을 반환하는 함수
  

1. Count

select count(column)
from tablename
where conditions;

2. Sum

select sum(column)
from tablename
where conditions;

3. Avg

select avg(column)
from tablename
where conditions;

4. Min

select min(column)
from tablename
where conditions;

5. Max

select max(column)
from tablename
where conditions;

6. Group by

• 그룹화하여 데이터를 조회

select column1, column2...
from table
where condition
group by column1, column2...
order by column1, column2...;

7. Having

• 조건에 집계함수가 포함되는 경우 where 대신 having 사용

select column1, column2...
from table
where condition
group by column1, column2...
having condition(Aggregate Functions) <- ex> case_number>4000
order by column1, column2...;