题解 | #删除记录（二）#

DELETE
FROM
	exam_record
WHERE
	(
		timestampdiff(
			MINUTE,
			start_time,
			submit_time
		) < 5
		OR submit_time IS NULL
	)
AND start_time IN (
	SELECT
		*
	FROM
		(
			SELECT
				start_time
			FROM
				exam_record
			WHERE
				timestampdiff(
					MINUTE,
					start_time,
					submit_time
				) < 5
			OR submit_time IS NULL
			ORDER BY
				start_time ASC
			LIMIT 3
		) a
)


timestampdiff or submit_time is null 去查询要求的值
用子查询去查找满足条件时start_time最小的3个值
同时，mysql环境中不允许先select一些值再delete，需要外层再套select * 解决