인프런 커뮤니티 질문&답변

-- 3. 평균 학점이 3.5미만인 학생은?

SELECT students.nickname AS "닉네임", ROUND(AVG(grade_points.point),2) AS "평균 학점"

FROM students

JOIN grades ON grades.student_id = students.id

JOIN grade_points ON grade_points.grade = grades.grade

GROUP BY students.nickname

HAVING 3.5 > AVG(grade_points.point)

;

-- 서브 쿼리 이용 답

SELECT students.nickname AS "닉네임", avg_grade_point.round AS "평균 학점"

FROM students

JOIN (-- 학생별_평균_학점

SELECT student_id, ROUND(AVG(point), 2)

FROM grades

JOIN grade_points ON grade_points.grade = grades.grade

GROUP BY student_id

HAVING AVG(point) < 3.5

) AS avg_grade_point ON avg_grade_point.student_id = students.id

;

서브 쿼리를 이용하려고 생각하는 게 좋을까요?

단순히 JOIN만 사용해서 할 수 있으면 JOIN만 써도 괜찮을까요..?

현업에서는 어떤 걸 더 많이 쓰게 될지 궁금합니다!