リレーションテーブルのクエリを支援する

SELECT  f.*
FROM    (
        SELECT  flashcard_id
        FROM    tags t
        JOIN    flashcard_tags ft
        ON      ft.tag_id = t.tag_id
        WHERE   t.name IN ('tag2', 'tag4')
        GROUP BY
                flashcard_id
        HAVING  COUNT(*) = 2
        ) ft
JOIN    flashcard f
ON      f.flashcard_id = ft.flashcard_id