1、获取指定时间区间内的所有日期

SELECT
	date_add( '2022-04-01', INTERVAL ( cast( help_topic_id AS signed INTEGER )) DAY ) day 
FROM
	mysql.help_topic 
WHERE
	help_topic_id < datediff( '2022-05-01', '2022-04-01' ) + 1 
ORDER BY
	help_topic_id

2、获取当天内所有时段

SELECT DATE_FORMAT( DATE_SUB( DATE_FORMAT( NOW(), '%Y-%m-%d' ), INTERVAL (-( @i := @i + 1 )) HOUR 
		),
	'%Y-%m-%d %H' 
) AS 'time' 
FROM
	(
	SELECT
		a 
	FROM
		( SELECT '1' AS a UNION SELECT '2' UNION SELECT '3' UNION SELECT '4' ) AS a
		JOIN ( SELECT '1' UNION SELECT '2' UNION SELECT '3' UNION SELECT '4' UNION SELECT '5' UNION SELECT '6' ) AS b ON 1 
	) AS b,
	( SELECT @i := - 1 ) AS i