计算两个时间戳相隔的毫秒数。但是你有2楼的疑问,不知道timestamp是什么意思,那就不好说了。
select extract(day from intv)*24*60*60*1000
+extract(hour from intv)*60*60*1000
+extract(minute from intv)*60*1000
+extract(second from intv)*1000
from (SELECT SYSTIMESTAMP-timestamp '2019-10-12 15:52:00' AS intv from dual);