;3学生表student：用于存储学生信息包括学生姓名、学生年龄、学生性别等。4教师表teacher：用于存储教师信息包括教师姓名、教师年龄、教师性别等的代码

CREATE TABLE course ( course_id INT PRIMARY KEY, course_name VARCHAR(50) NOT NULL, credit INT NOT NULL, teacher_id INT, FOREIGN KEY (teacher_id) REFERENCES teacher(teacher_id) );

CREATE TABLE student ( student_id INT PRIMARY KEY, student_name VARCHAR(50) NOT NULL, age INT NOT NULL, gender VARCHAR(10) NOT NULL );

CREATE TABLE teacher ( teacher_id INT PRIMARY KEY, teacher_name VARCHAR(50) NOT NULL, age INT NOT NULL, gender VARCHAR(10) NOT NULL );