Question

当我尝试为表声明多个外键时，我不断收到错误“＃1215 - 无法添加外键约束”。我知道可以在表中声明多个外键，所以我不确定为什么我收到错误。我很确定我的错误与引用多值主键有关，但我不确定如何修复它。非常感谢所有帮助，并提前感谢您！

编辑：前4个表正常工作。最后4个是我遇到麻烦的。

以下是我的表格：

CREATE TABLE Course (
CourseNo INT NOT NULL, 
CourseName VARCHAR(40) NOT NULL, 
Department VARCHAR(40) NOT NULL, 
PRIMARY KEY(CourseNo)
);

CREATE TABLE Student (
SSN INT NOT NULL, 
FirstName VARCHAR(15) NOT NULL, 
LastName VARCHAR(30) NOT NULL, 
Street VARCHAR(40) NOT NULL, 
City VARCHAR(40) NOT NULL, 
State VARCHAR(30) NOT NULL, 
Zip MEDIUMINT NOT NULL, 
PRIMARY KEY(SSN)
);

CREATE TABLE ClassRoom (
RoomNo INT NOT NULL, 
Building VARCHAR(25) NOT NULL, 
Capacity INT NOT NULL, 
/* CONSTRAINT pk_ClassID */ PRIMARY KEY(RoomNo, Building)
);

CREATE TABLE Section (
CourseNumber INT NOT NULL, 
SectionNo INT NOT NULL, 
Instructor VARCHAR(40) NOT NULL, 
/*CONSTRAINT pk_SectionID*/ PRIMARY KEY(CourseNumber, SectionNo), 
FOREIGN KEY (CourseNumber) REFERENCES Course(CourseNo)
);

CREATE TABLE Enrolls (
StuSSN INT NOT NULL, 
SecNo INT NOT NULL, 
CNo INT NOT NULL, 
/* CONSTRAINT pk_EnrollID */ PRIMARY KEY(StuSSN, SecNo, CNo), 
FOREIGN KEY (StuSSN) REFERENCES Student(SSN), 
FOREIGN KEY (SecNo) REFERENCES Section(SectionNo), 
FOREIGN KEY (CNo) REFERENCES Course(CourseNo)
);

CREATE TABLE Exam (
CNum INT NOT NULL, 
SectionNum INT NOT NULL, 
ExamNo INT NOT NULL, 
E_Date DATE NOT NULL, 
E_Time TIME NOT NULL, 
/* CONSTRAINT pk_ExamID */ PRIMARY KEY(CNum, SectionNum, ExamNo), 
FOREIGN KEY (CNum) REFERENCES Course(CourseNo), 
FOREIGN KEY (SectionNum) REFERENCES Section(SectionNo)
);

CREATE TABLE Takes (
StudentSSN INT NOT NULL, 
CourseNum INT NOT NULL, 
SecNum INT NOT NULL, 
ExamNum INT NOT NULL, 
Result TINYINT NOT NULL, 
/* CONSTRAINT pk_TakesID */ PRIMARY KEY(StudentSSN, CourseNum, SecNum, ExamNum), 
FOREIGN KEY (StudentSSN) REFERENCES Student(SSN), 
FOREIGN KEY (CourseNum) REFERENCES Course(CourseNo), 
FOREIGN KEY (SecNum) REFERENCES Section(SectionNo), 
FOREGIN KEY (ExamNum) REFERENCES Exam(ExamNo)
);

CREATE TABLE ConductedIn (
RoomNum INT NOT NULL, 
Build VARCHAR(25) NOT NULL, 
CNumber INT NOT NULL, 
SectionNumber INT NOT NULL, 
ExamNumber INT NOT NULL, 
/* CONSTRAINT pk_ConductedID */ PRIMARY KEY(RoomNum, Build, CNumber, SectionNumber, ExamNumber), 
FOREIGN KEY (RoomNum) REFERENCES ClassRoom(RoomNo), 
FOREIGN KEY (Build) REFERENCES ClassRoom(Building), 
FOREIGN KEY (CNumber) REFERENCES Course(CourseNo), 
FOREIGN KEY (SectionNumber) REFERENCES Section(SectionNo), 
FOREIGN KEY(ExamNumber) REFERENCES Exam(ExamNo)
);

Answer 1

我会在这里向您推荐更多详情：MySQL Foreign Key Error 1005 errno 150

基本上您的问题是，在Section表中，您有一个复合主键PRIMARY KEY(CourseNumber, SectionNo)，在Enrolls表格中，您尝试引用字段SectionNo表Section，但该字段没有索引。任何引用的字段都必须有索引。

因此，请确保您作为外键引用的任何字段都有自己的索引（例如PRIMARY(fieldname) UNIQUE(fieldname) INDEX(fieldname)）

如何在mysql中声明引用多值主键的外键？

1 个答案: