mysql - 无法添加外键约束为主外键

Question

我得到了

Error Code: 1215. Cannot add foreign key constraint 0.172 sec

我不知道我做错了什么。我确保外键是主键。我的 SQL:

CREATE TABLE Student (
StudentID INT(6) NOT NULL,
StudName VARCHAR(15) NOT NULL,
StudEmail VARCHAR(15) NOT NULL,
StudeHomeNum INT(10) NOT NULL,
StudCellPhoneNum INT(10) NOT NULL,
CourseCode INT(6) NOT NULL,
ProgramCode INT(6) NOT NULL,
PRIMARY KEY (StudentID),
FOREIGN KEY (CourseCode)
    REFERENCES Course (CourseCode)
);

CREATE TABLE Course (
CourseCode INT(6) PRIMARY KEY NOT NULL,
CourseName VARCHAR(15) NOT NULL,
Prequisites VARCHAR(15) NOT NULL
);

Answer 1

由于 Student 表中的 CourseCode 代码列正在引用 Course 表，因此您必须先创建 Course 表.如下更改您的sql代码

CREATE TABLE Course (
CourseCode INT(6) PRIMARY KEY NOT NULL,
CourseName VARCHAR(15) NOT NULL,
Prequisites VARCHAR(15) NOT NULL
);

CREATE TABLE Student (
StudentID INT(6) NOT NULL,
StudName VARCHAR(15) NOT NULL,
StudEmail VARCHAR(15) NOT NULL,
StudeHomeNum INT(10) NOT NULL,
StudCellPhoneNum INT(10) NOT NULL,
CourseCode INT(6) NOT NULL,
ProgramCode INT(6) NOT NULL,
PRIMARY KEY (StudentID),
FOREIGN KEY (CourseCode)
    REFERENCES Course (CourseCode)
);