[G_SQL] p.156 : 조인에서 GROUP BY를 사용하기

-- [G_SQL] p.156 : 조인에서 GROUP BY를 사용하기
-- Calculus IV 과목의 성별 학생 수를 구하라.
SELECT gender, COUNT(student_name) AS number
    FROM students, enrolls, courses
    WHERE course_name = 'Calculus IV' AND
        COURSES.course = ENROLLS.course AND
        ENROLLS.student = STUDENTS.student
    GROUP BY gender;   

-- [G_SQL] p.156 : 조인에서 GROUP BY를 사용하기
-- Calculus IV 과목의 성별 학생 수를 구하라.
-- INNER JOIN 버전
SELECT gender, COUNT(student_name) AS number
    FROM (students
                INNER JOIN ENROLLS
                ON ENROLLS.student = STUDENTS.student)
            INNER JOIN COURSES
            ON COURSES.course = ENROLLS.course
        WHERE course_name = 'Calculus IV'
        GROUP BY gender;