[G_SQL] p.178 : '>'를 이용한 상관부질의

-- [G_SQL] p.178 : '>'를 이용한 상관부질의
-- 반에서 평균보다 높은 학점을 받은 학생은 누구인가?
SELECT student_name, grade, course, section
    FROM students, enrolls E
    WHERE STUDENTS.student = E.student AND
        grade >
            (SELECT AVG(grade)
                FROM enrolls
                WHERE course = E.course AND
                    section = E.section )
    ORDER BY course;