Mysql 8.0 查询每个分组top n的最简单快速的方法：

SELECT * FROM (
	SELECT dev_id, di_channel, di_preset, di_capture_time, di_filename, RANK() OVER (
		PARTITION BY dev_id, di_channel, di_preset
		ORDER BY di_capture_time DESC
	) seq
	FROM tb_device_image 
	WHERE di_capture_time > DATE_SUB(NOW(), INTERVAL 3 DAY)
) a
WHERE seq < 4