外键多字段帮助

Question

我有两个表

TABLE CLASS
(
    school varchar(50),
    year   varchar(50),
    grade  varchar(50),
    className varchar(50),
    PRIMARY KEY (school,year,grade,className)
)
TABLE STUDENT
(
    student_id varchar(50) PRIMARY KEY,
    detail varchar(50)
)

现在，我想为学生创建子类。如何创建引用?

Answer 1

就照着别人做的去做…

CREATE TABLE CLASS (
    id int not null auto_increment PRIMARY KEY, -- CREATE A KEY COLUMN
    school varchar(50),
    year   varchar(50),
    grade  varchar(50),
    className varchar(50),
    unique (school,year,grade,className)
);
CREATE TABLE STUDENT (
    student_id varchar(50) PRIMARY KEY,
    class_id int references class,  -- REFERENCE THE KEY
    detail varchar(50)
);