创建学生表，课程表，班级表，班级课程表

首先创建班级表，因为班级跟学生为一对多关系，先创建班级表能在学生表中插入外键

班级表

CREATE TABLE banji(id INT PRIMARY KEY AUTO_INCREMENT,`name` VARCHAR(10) NOT NULL
);
INSERT INTO banji(`name`)VALUES('class1'),('class2');
SELECT * FROM banji;

 CREATE TABLE student(id INT PRIMARY KEY AUTO_INCREMENT,`name` VARCHAR(10) NOT NULL,age INT,gender CHAR(1),banji_id INT,FOREIGN KEY(banji_id) REFERENCES banji(id)
);
INSERT INTO student(`name`,age,gender,banji_id) 
VALUES('张三',20,'男',1),('李四',21,'男',2),('王五',20,'女',1);SELECT * FROM student;

创建课程表

CREATE TABLE course(id INT PRIMARY KEY AUTO_INCREMENT,NAME CHAR(10)NOT NULL,credit INT
);INSERT INTO course(NAME,credit) VALUES('Chinese',5),('Math',4),(English,4）;SELECT * FROM course；

创建班级课程表

班级跟课程之间的关系为多对多

创建班级课程表，将banji_id,course_id作为外键，称为联合主键

CREATE TABLE banji_course(banji_id INT,course_id INT,PRIMARY KEY(banji_id,course_id),FOREIGN KEY(banji_id) REFERENCES banji(id),FOREIGN KEY(course_id) REFERENCES course(id)
);
INSERT INTO banji_course(banji_id,course_id) VALUES(1,1),(1,3),(2,1),(2,2),(2,3);
SELECT * FROM banji_course;