如何设计一个高效的MySQL表结构来实现音频播放功能？

CREATE TABLE audio (
  `id` INT PRIMARY KEY AUTO_INCREMENT,
  `name` VARCHAR(100) NOT NULL,
  `path` VARCHAR(255) NOT NULL,
  `duration` INT NOT NULL,
  `created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE playback_record (
  `id` INT PRIMARY KEY AUTO_INCREMENT,
  `user_id` INT NOT NULL,
  `audio_id` INT NOT NULL,
  `played_duration` INT NOT NULL,
  `created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
  FOREIGN KEY (`user_id`) REFERENCES `user`(`id`),
  FOREIGN KEY (`audio_id`) REFERENCES `audio`(`id`)
);

-- 插入音频信息
INSERT INTO audio (`name`, `path`, `duration`) VALUES ('音频1', '/path/audio1.mp3', 120);
INSERT INTO audio (`name`, `path`, `duration`) VALUES ('音频2', '/path/audio2.mp3', 180);
INSERT INTO audio (`name`, `path`, `duration`) VALUES ('音频3', '/path/audio3.mp3', 240);

-- 插入播放记录
INSERT INTO playback_record (`user_id`, `audio_id`, `played_duration`) VALUES (1, 1, 60);
INSERT INTO playback_record (`user_id`, `audio_id`, `played_duration`) VALUES (1, 2, 90);
INSERT INTO playback_record (`user_id`, `audio_id`, `played_duration`) VALUES (2, 1, 30);

SELECT `audio`.`name`, `played_duration`
FROM `playback_record`
INNER JOIN `audio` ON `playback_record`.`audio_id` = `audio`.`id`
WHERE `user_id` = 1;

UPDATE `playback_record`
SET `played_duration` = 120
WHERE `user_id` = 1 AND `audio_id` = 1;