mysql获取当天时间0点到当前时间点

就是mysql要怎么获取从当天时间的0点到当前时间点，在网上找到的是当天的所有时间点

select 
    LEFT(
        DATE_ADD(CURDATE(),INTERVAL (CAST(help_topic_id as signed) - 24) hour),
        13
        ) as date
from
    mysql.help_topic
where
    help_topic_id < 24
ORDER BY help_topic_id

我把24修改成select hour(CURTIME())，报错了，请问有什么办法吗，万分感谢

BETWEEN DATE_FORMAT(NOW(),'%Y-%m-%d 00:00:00') AND NOW()