1、获取系统时间的语句(ssxff6获取小数点后面六位)select sysdate,systimestamp,to_char(systimestamp, 'yyyymmdd hh24:mi:ssxff6'), to_char(systimestamp, 'yyyymmdd hh24:mi:ss.ff6') from dual;
2、字符型转成timestamp
select to_timestamp('2011-09-14 12:52:42.123456789', 'syyyy-mm-dd hh24:mi:ss.ff') from dual;
3、timestamp转成date型
selectcast(to_timestamp('2011-09-14 12:52:42.123456789', 'syyyy-mm-dd hh24:mi:ss.ff') asdate) timestamp_to_date from dual;
4、date型转成timestamp
selectcast(sysdate astimestamp) date_to_timestamp from dual;
5、两date的日期相减得出的是天数,而两timestamp的日期相减得出的是完整的年月日时分秒小数秒
select sysdate-sysdate,systimestamp-systimestamp from dual;
select extract(dayfrom inter) * 24 * 60 * 60 +
extract(hourfrom inter) * 60 * 60 + extract(minutefrom inter) * 60 +
extract(secondfrom inter) "seconds"from
(
select to_timestamp('2011-09-14 12:34:23.281000000', 'yyyy-mm-dd hh24:mi:ss.ff') -
to_timestamp('2011-09-14 12:34:22.984000000', 'yyyy-mm-dd hh24:mi:ss.ff') inter from dual
);
select extract(secondfrom to_timestamp('2011-09-14 12:34:23.281000000', 'yyyy-mm-dd hh24:mi:ss.ff'))-
extract(secondfrom to_timestamp('2011-09-14 12:34:22.984000000', 'yyyy-mm-dd hh24:mi:ss.ff')) from dual;
注:所以,timestamp 要算出两日期间隔了多少秒,要用函数转换一下。
to_char 函数支持 date 和 timestamp, 但是 trunc 却不支持 TIMESTAMP 数据类型。
--转自