oracle日期时间型timestamp的深入理解

select to_timestamp('01-10月-08 07.46.41.000000000 上午','dd-MON-yy hh:mi:ss.ff AM')
from dual;

select cast(to_timestamp('01-10月-08 07.46.41.000000000 上午','dd-MON-yy hh:mi:ss.ff AM') as date) timestamp_to_date
from dual;

select cast(sysdate as timestamp) date_to_timestamp
from dual;

select systimestamp from dual;