mysql 设置表多对多关系

CREATE TABLE students (
    id INT PRIMARY KEY,
    name VARCHAR(100)
);

CREATE TABLE courses (
    id INT PRIMARY KEY,
    name VARCHAR(100)
);

CREATE TABLE student_courses (
    student_id INT,
    course_id INT,
    PRIMARY KEY (student_id, course_id),
    FOREIGN KEY (student_id) REFERENCES students(id),
    FOREIGN KEY (course_id) REFERENCES courses(id)
);

INSERT INTO students (id, name) VALUES (1, 'Alice');
INSERT INTO students (id, name) VALUES (2, 'Bob');

INSERT INTO courses (id, name) VALUES (101, 'Math');
INSERT INTO courses (id, name) VALUES (102, 'Science');

INSERT INTO student_courses (student_id, course_id) VALUES (1, 101);
INSERT INTO student_courses (student_id, course_id) VALUES (1, 102);
INSERT INTO student_courses (student_id, course_id) VALUES (2, 101);

SELECT s.name AS student_name, c.name AS course_name
FROM students s
JOIN student_courses sc ON s.id = sc.student_id
JOIN courses c ON sc.course_id = c.id;

ALTER TABLE student_courses
ADD CONSTRAINT fk_student_courses_student FOREIGN KEY (student_id) REFERENCES students(id),
ADD CONSTRAINT fk_student_courses_course FOREIGN KEY (course_id) REFERENCES courses(id);

CREATE INDEX idx_student_courses_student_id ON student_courses(student_id);
CREATE INDEX idx_student_courses_course_id ON student_courses(course_id);