SQL phpMyAdmin-找不到外键约束

Question

在我在phpmyadmin上创建表艺术家和表专辑后，当我尝试创建表轨道时，我会遇到错误 - ＃1215-无法添加外键约束。可以来自null吗？

CREATE TABLE Artist (
artist_id INTEGER NOT NULL AUTO_INCREMENT,
name VARCHAR(255),
PRIMARY KEY(artist_id)
)
CREATE TABLE Album (
album_id INTEGER NOT NULL AUTO_INCREMENT,
title VARCHAR(255),
artist_id INTEGER,
PRIMARY KEY(album_id),
INDEX USING BTREE (title),
CONSTRAINT FOREIGN KEY (artist_id)
REFERENCES Artist (artist_id)
ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE = InnoDB;

CREATE TABLE Track (  <--ERROR STARTS AFTER I TRY TO CREATE TRACK.
track_id INTEGER NOT NULL AUTO_INCREMENT,
title VARCHAR(255),
len INTEGER,
rating INTEGER,
count INTEGER,
album_id INTEGER,
genre_id INTEGER,
PRIMARY KEY(track_id),
INDEX USING BTREE (title),
CONSTRAINT FOREIGN KEY (album_id) REFERENCES Album (album_id)
  ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT FOREIGN KEY (genre_id) REFERENCES Album (genre_id)
  ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE = InnoDB;

Answer 1

您对以下语句

有问题

CONSTRAINT FOREIGN KEY (genre_id) REFERENCES Album (genre_id)
   ON DELETE CASCADE ON UPDATE CASCADE

genre_id不是Album表的列。

此外，将仅使用另一个表的主键创建外键...