小编tig*_*ger的帖子

这是sql中的两个声明

create table bookAdoption
(   
    courseId int,
    sem int,
    isbn int,
    PRIMARY KEY(courseId, sem, isbn),       
    FOREIGN KEY(courseId) REFERENCES course(courseId),
    FOREIGN KEY(sem) REFERENCES enroll(sem)
);

而另一个

CREATE TABLE bookAdoption
(
    courseId INT REFERENCES course(courseId) ,
    sem INT REFERENCES enroll(sem),
    isbn INT REFERENCES text1(isbn),
    PRIMARY KEY(courseId, sem, isbn)

);

只使用references关键字有什么区别

并同时使用引用和外来关键字