質問と回答機能を実装するために柔軟な MySQL テーブル構造を設計するにはどうすればよいでしょうか?

CREATE TABLE users (
    id INT PRIMARY KEY AUTO_INCREMENT,
    username VARCHAR(255) NOT NULL,
    password VARCHAR(255) NOT NULL,
    email VARCHAR(255) NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE questions (
    id INT PRIMARY KEY AUTO_INCREMENT,
    user_id INT NOT NULL,
    title VARCHAR(255) NOT NULL,
    content TEXT NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    FOREIGN KEY (user_id) REFERENCES users(id)
);

CREATE TABLE answers (
    id INT PRIMARY KEY AUTO_INCREMENT,
    question_id INT NOT NULL,
    user_id INT NOT NULL,
    content TEXT NOT NULL,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    FOREIGN KEY (question_id) REFERENCES questions(id),
    FOREIGN KEY (user_id) REFERENCES users(id)
);

CREATE TABLE tags (
    id INT PRIMARY KEY AUTO_INCREMENT,
    name VARCHAR(255) NOT NULL
);

CREATE TABLE question_tags (
    question_id INT NOT NULL,
    tag_id INT NOT NULL,
    PRIMARY KEY (question_id, tag_id),
    FOREIGN KEY (question_id) REFERENCES questions(id),
    FOREIGN KEY (tag_id) REFERENCES tags(id)
);

INSERT INTO questions (user_id, title, content)
VALUES (1, '如何设计一个灵活的MySQL表结构', '请问質問と回答機能を実装するために柔軟な MySQL テーブル構造を設計するにはどうすればよいでしょうか?');

INSERT INTO answers (question_id, user_id, content)
VALUES (1, 2, '你可以设计一个问题表、回答表和标签表来实现问答功能。');

INSERT INTO tags (name)
VALUES ('数据库'), ('问答');

INSERT INTO question_tags (question_id, tag_id)
VALUES (1, 1), (1, 2);

SELECT q.title, q.content, u.username, a.content
FROM questions q
JOIN users u ON q.user_id = u.id
JOIN answers a ON q.id = a.question_id
WHERE q.id = 1;