[G_SQL] p.180 : ALL을 사용한 상관부질의

-- [G_SQL] p.180 : ALL을 사용한 상관부질의
-- 남학생만 수강하는 과목은?
SELECT DISTINCT course_name
    FROM courses C
    WHERE 'M' = ALL
        (SELECT gender
            FROM enrolls, students
                WHERE ENROLLS.student = STUDENTS.student AND
                    ENROLLS.course = C.course );