집계함수
count : 갯수
select count(*)
from police_station;
select count(distinct crime_type)
from crime_status;
sum : 합
select sum(case_number)
from crime_status
where status_type='발생';
avg : 숫자컬럼의 평균 계산
select avg(case_number)
from crime_status
where status_type='발생' and police_station like '중부';
min : 가장 작은 값
select min(case_number)
from crime_status
where crime_type = '강도' and status_type = '발생';
max : 가장 큰 값
select max(case_number)
from crime_status
where crime_type = '살인';
group by : 그룹화하여 데이터 조회
select police_station, sum(case_number) 발생건수
from crime_status
where status_type = '발생'
group by police_station
order by 발생건수 desc;
having : 조건에 집계함수가 포함되는 경우 where 대신 having 사용
select police_station, sum(case_number) count
from crime_status
where status_type = '발생'
group by police_station
having count > 4000
