無法以外鍵為主鍵添加外鍵約束

Question

我正在

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

我不知道我在做什么錯。 我確保外鍵是主鍵。 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

由於Student表中的CourseCode代碼列引用了Course表，因此您必須首先創建Course表。 如下更改您的SQL代碼

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)
);