无法添加外键约束错误 1215 HY000

Question

我的 ENROLLS table、TAKES table、CONDUCTED_IN table 和 EXAM table 一直收到此错误。当我将创建的 table 上传到数据库时。我不确定是什么问题有人可以帮忙吗？ COURSE、SECTION、CLASS_ROOM 和 STUDENT tables 已添加到数据库中，其他的有问题。

create table COURSE(
CourseNo varchar(10),
Course_Name varchar(30),
Department varchar(25),
primary key(CourseNo)
);

create table SECTION(
CourseNo varchar(10),
SectionNo varchar(2),
primary key(CourseNo, SectionNo),
foreign key(CourseNo) references COURSE(CourseNo)
);

create table ENROLLS(
SSN char(9),
SectionNo varchar(2),
CourseNo varchar(10),
primary key(SSN, CourseNo, SectionNo),
foreign key(SSN) references STUDENT(SSN),
foreign key(SectionNo) references SECTION(SectionNo),
foreign key(CourseNo) references SECTION(CourseNo)
);

create table STUDENT(
SSN char(9),
First_Name varchar(20),
Last_Name varchar(20),
Street varchar(15),
City varchar(15),
Zip char(5),
State varchar(20),
primary key(SSN)
);

create table TAKES(
SSN char(9),
CourseNo varchar(10),
SectionNo varchar(2),
ExamNo char(3),
Result char(1),
primary key(SSN, CourseNo, SectionNo, ExamNo),
foreign key(SSN) references STUDENT(SSN),
foreign key(CourseNo) references EXAM(CourseNo),
foreign key(SectionNo) references EXAM(SectionNo),
foreign key(ExamNo) references EXAM(ExamNo)
);

create table EXAM(
CourseNo varchar(10),
SectionNo varchar(2),
ExamNo char(3),
primary key(CourseNo, SectionNo, ExamNo),
foreign key(CourseNo) references SECTION(CourseNo),
foreign key(SectionNo) references SECTION(SectionNo)
);

create table CONDUCTED_IN(
RoomNo int,
Building varchar(30),
CourseNo varchar(10),
SectionNo varchar(2),
ExamNo char(3),
primary key(RoomNo, Building, CourseNo, SectionNo, ExamNo),
foreign key(RoomNo) references CLASS_ROOM(RoomNo),
foreign key(Building) references CLASS_Room(Building),
foreign key(CourseNo) references EXAM(CourseNo),
foreign key(SectionNo) references EXAM(SectionNo),
foreign key(ExamNo) references EXAM(ExamNo)
);

create table CLASS_ROOM(
RoomNo int,
Building varchar(30),
Capacity int,
primary key(RoomNo, Building)
);

Answer 1

您的代码中的问题与关系管理有关

tables必须按顺序创建；当一个 table 通过外键引用另一个 table 时，它必须在在父 table
你的大多数 table 都有 复合主键 （即使用多列的主键） - 所以你需要 复合外键：与其在关系的每个相关列上创建多个外键，不如使用一个多列键一次引用列的元组

考虑到这些基本原则，这里是您的代码的更新版本，可以正常运行 in this DB Fiddle。

create table COURSE(
    CourseNo varchar(10),
    Course_Name varchar(30),
    Department varchar(25),
    primary key(CourseNo)
);

create table CLASS_ROOM(
    RoomNo int,
    Building varchar(30),
    Capacity int,
    primary key(RoomNo, Building)
);

create table STUDENT(
    SSN char(9),
    First_Name varchar(20),
    Last_Name varchar(20),
    Street varchar(15),
    City varchar(15),
    Zip char(5),
    State varchar(20),
    primary key(SSN)
);

create table SECTION(
    CourseNo varchar(10),
    SectionNo varchar(2),
    primary key(CourseNo, SectionNo),
    foreign key(CourseNo) references COURSE(CourseNo)
);

create table ENROLLS(
    SSN char(9),
    SectionNo varchar(2),
    CourseNo varchar(10),
    primary key(SSN, CourseNo, SectionNo),
    foreign key(SSN) references STUDENT(SSN),
    foreign key(CourseNo, SectionNo) references SECTION(CourseNo, SectionNo)
);

create table EXAM(
    CourseNo varchar(10),
    SectionNo varchar(2),
    ExamNo char(3),
    primary key(CourseNo, SectionNo, ExamNo),
    foreign key(CourseNo, SectionNo) references SECTION(CourseNo, SectionNo)
);

create table TAKES(
    SSN char(9),
    CourseNo varchar(10),
    SectionNo varchar(2),
    ExamNo char(3),
    Result char(1),
    primary key(SSN, CourseNo, SectionNo, ExamNo),
    foreign key(SSN) references STUDENT(SSN),
    foreign key(CourseNo, SectionNo, ExamNo) references EXAM(CourseNo, SectionNo, ExamNo)
);

create table CONDUCTED_IN(
    RoomNo int,
    Building varchar(30),
    CourseNo varchar(10),
    SectionNo varchar(2),
    ExamNo char(3),
    primary key(RoomNo, Building, CourseNo, SectionNo, ExamNo),
    foreign key(RoomNo, Building) references CLASS_ROOM(RoomNo, Building),
    foreign key(CourseNo, SectionNo, ExamNo) references EXAM(CourseNo, SectionNo, ExamNo)
);

无法添加外键约束错误 1215 HY000

Cannot add foreign key constraint error 1215 HY000

mysql

sql

database

foreign-keys

create-table