关于数据库中timestamp类型 转换问题

1.

select to_char(systimestamp,'yyyy-mm-dd hh24:mi:ssxff') time1,to_char(current_timestamp) time2 from dual;

2.

SELECT to_timestamp('27-01-2015 13:12:44.436000', 'dd-mm-yyyy hh24:mi:ss.ff') time FROM dual;

3.由2可以推出

SELECT to_timestamp(to_char(systimestamp,'dd-mm-yyyy hh24:mi:ssxff'), 'dd-mm-yyyy hh24:mi:ss.ff') time FROM dual;