MySQL外键约束 一对多 多对多

-- 专辑父表 --- 曲目 子表  --- 一对多
alter table song add music_id int;


update song set music_id = 1;

alter table song  ADD CONSTRAINT fk_user_music FOREIGN KEY (music_id)
references music(id);

-- 专辑 -- 短评   1  --M
ALTER TABLE review ADD music_id int ;
UPDATE review SET music_id =1;

ALTER TABLE review ADD CONSTRAINT fk_music_review FOREIGN KEY(music_id)
REFERENCES music(id);

-- 专辑 -- 用户 -- M---M
CREATE TABLE tb_music_user(
    id int AUTO_INCREMENT PRIMARY KEY ,
    music_id INT ,
    user_id INT,
    FOREIGN KEY (user_id) REFERENCES user(id),
    FOREIGN KEY (music_id) REFERENCES music(id)

);