SQL 알고리즘 코드카타(카테고리 별 상품 개수 구하기) 26.04.08(수)

1. 문제 링크:https://school.programmers.co.kr/learn/courses/30/lessons/131529
2. 정답 코드: 

select
    left(product_code, 2) as category,
    count(left(product_code, 2)) as products
from product
group by left(product_code, 2)
order by category

3. 오류 상황:

select
    left(product_code, 2) as category,
    count(left(product_code, 2)) as products
from product
order by category

=> 집계함수 외 그룹화 누락

4. 시도 방법:

=> 그룹화 추가

5. 최종 문제 해결 방법:

=> group by로 집계함수 외 컬럼 그룹화