mysql - 我该如何解决 'Error Cannot add foreign key constraint'？

Question

所以我使用 sqlfiddle 但总是收到错误“无法添加外键约束”。有人可以帮我找到错误吗？我确定问题出在第一个表(教授)上，就像删除两个 FK 约束一样，代码可以完美运行。

CREATE TABLE Professor (
Inicials char(2) not null,
nom varchar(30),
DNI varchar(10),
Email varchar(30),
CONSTRAINT inicials_pk PRIMARY KEY (Inicials),
CONSTRAINT dni_professor UNIQUE (DNI),
CONSTRAINT Email_professor UNIQUE (Email)
);

INSERT INTO Professor (Inicials, nom, DNI, Email)
VALUES ('JF','Joel Ferragut','56783698V','jferragut@iesmontisa.org');
INSERT INTO Professor (Inicials, nom, DNI, Email)
VALUES ('AE','Aleix Esteve','56983698V','aesteve@iesmontisa.org');
INSERT INTO Professor (Inicials, nom, DNI, Email)
VALUES ('KC','Kevin Costes','56883698V','kevincostes@iesmontisa.org');

CREATE TABLE Grup (
Nivell varchar(10),
Curs varchar(10),
Lletra varchar(5),
Aula varchar(5),
CONSTRAINT GrupNivell_pk PRIMARY KEY (Nivell, Curs, Lletra)
);

INSERT INTO Grup (Nivell, Curs, Lletra, Aula)
VALUES ('1','2018-2019','A','24');

CREATE TABLE Docencia (
hores_totals int,
Inicials char(2) not null,
Nivell varchar(10),
Curs varchar(10),
Lletra varchar(5),
CONSTRAINT profe FOREIGN KEY (inicials)
REFERENCES Professors (inicials),
CONSTRAINT GrupNivell_pk FOREIGN KEY (Nivell, Curs, Lletra)
REFERENCES Grup (Nivell, Curs, Lletra)
);

Answer 1

这是一个拼写错误，您的表称为Professor，您的外键引用Professors。

试试这个:

CREATE TABLE Docencia (
hores_totals int,
Inicials char(2) not null,
Nivell varchar(10),
Curs varchar(10),
Lletra varchar(5),
CONSTRAINT profe FOREIGN KEY (Inicials) REFERENCES Professor (Inicials),
CONSTRAINT GrupNivell_pk FOREIGN KEY (Nivell, Curs, Lletra) REFERENCES Grup (Nivell, Curs, Lletra)
);