用DATESUBDATE函数,取时分秒,然后拼接
或者转换时分秒

RIGHT(TIME(TRUNC(DATESUBDATE("2021/7/25 9:32:26","2021/7/25 9:26:25","s")/3600),TRUNC(MOD(DATESUBDATE("2021/7/25 9:32:26","2021/7/25 9:26:25","s"),3600)/60),MOD(DATESUBDATE("2021/7/25 9:32:26","2021/7/25 9:26:25","s"),60)),8)
