Sql Fiddle errors

Question

我正在尝试为SQL Fiddle中的赋值创建SQL语句，但我一直收到错误"；无法添加外键约束"；。我尝试过各种各样的事情，但当我改变事情时，我会遇到不同的错误。我做错了什么？

CREATE TABLE Person (
ID int NOT NULL,
FName varchar(255),
LName varchar(255),
Preferred_Name varchar(255),
PRIMARY KEY (ID)
)
;

CREATE TABLE Song (
ID varchar(255) NOT NULL,
Title varchar(255),
Run_Time varchar(255),
Lyrics varchar(255),
LeadID int,
FOREIGN KEY (LeadID) REFERENCES Person(ID),
PRIMARY KEY (ID)
)
;

CREATE TABLE Album (
Title varchar(255) NOT NULL,
Run_Time int,
Release_Year TIMESTAMP,
PRIMARY KEY (Title)
)
;

CREATE TABLE Has (
Album_Title varchar(255),
Song_Title varchar(255),
FOREIGN KEY (Album_Title) REFERENCES Album(Title),
FOREIGN KEY (Song_Title) REFERENCES Song(ID)
)
;

CREATE TABLE Part_Of (
PersonID int,
SongID int,
Role varchar(255) NOT NULL,
FOREIGN KEY (PersonID) REFERENCES Person(ID),
FOREIGN KEY (SongID) REFERENCES Song(ID),
PRIMARY KEY (Role)
)
;

Answer 1

在Song和Has表中，您将Song.ID和Has.Song_Title定义为varchar(255(。在Part_Of表中，您将SongID定义为int。这就是外键失败的原因。在所有表中使用相同的数据类型(INT似乎是一个不错的选择(来解决此问题。

CREATE TABLE Song (
ID varchar(255) NOT NULL, <------
Title varchar(255),
Run_Time varchar(255),
Lyrics varchar(255),
LeadID int,
FOREIGN KEY (LeadID) REFERENCES Person(ID),
PRIMARY KEY (ID)
)
;
CREATE TABLE Has (
Album_Title varchar(255),
Song_Title varchar(255), <-----
FOREIGN KEY (Album_Title) REFERENCES Album(Title),
FOREIGN KEY (Song_Title) REFERENCES Song(ID)
)
;

CREATE TABLE Part_Of (
PersonID int,
SongID int, <-----
Role varchar(255) NOT NULL,
FOREIGN KEY (PersonID) REFERENCES Person(ID),
FOREIGN KEY (SongID) REFERENCES Song(ID),
PRIMARY KEY (Role)
)
;