Oracle 时区(TimeZone ） -- 数据类型

不 同数据类型的区别

使用 DBTimeZone 察看数据库所在的时区

SQL> select dbtimezone from dual;

DBTIMEZONE

----------

+08:00

找2个典型的美国时区

SQL> select tz_offset('US/Eastern'),tz_offset('US/Mountain') from dual;

TZ_OFFSET('US/EASTERN') TZ_OFFSET('US/MOUNTAIN')

----------------------- ------------------------

-05:00                  -07:00

建立表，包含不同类型的三个column

create table tstz(ts timestamp, tstz timestamp with time zone, tsltz timestamp with local time zone);

insert into tstz values(systimestamp,systimestamp,systimestamp);

commit; 

 
下面构造一个场景，用三个不同的时区的session来查询同样的数据

SQL>

SQL> alter session set NLS_TIMESTAMP_TZ_FORMAT = 'yyyy/mm/dd hh24:mi:ssxff TZH:TZM';

SQL> alter session set NLS_TIMESTAMP_FORMAT = 'yyyy/mm/dd hh24:mi:ssxff';

使用 SessionTimeZone 察看当前session的时区信息

SQL> select sessiontimezone from dual;

SESSIONTIMEZONE

---------------------------------------------------------------------------

+08:00

SQL> select * from tstz;

TS                                                TSTZ                                              TSLTZ  +08:00

------------------------------------------------- ------------------------------------------------- -------------------------------------------------

2008/03/29 10:14:10.774754                        2008/03/29 10:14:10.774754 +08:00                 2008/03/29 10:14:10.774754

SQL> alter session set time_zone = 'US/Mountain';

SQL> select * from tstz;

TS                                                TSTZ                                              TSLTZ  -07:00

------------------------------------------------- ------------------------------------------------- -------------------------------------------------

2008/03/29 10:14:10.774754                        2008/03/29 10:14:10.774754 +08:00                 2008/03/28 19:14:10.774754

SQL> alter session set time_zone = 'US/Eastern';

SQL> select * from tstz;

TS                                                TSTZ                                              TSLTZ  -05:00

------------------------------------------------- ------------------------------------------------- -------------------------------------------------

2008/03/29 10:14:10.774754                        2008/03/29 10:14:10.774754 +08:00                 2008/03/28 21:14:10.774754

从 高亮部分可以发现

timestamp with time zone 保存了insert的时区， 并且不 论在什么地方查询，显示结果都是一致的

timestamp with local time zone 保存的是一个内部的时区信息， 在不同 时区进行查询，都会自动转换成当前时区进行显示。

因为修改了session的时 区信息，所以系统时区和当前session时区不同

SQL> select systimestamp, current_timestamp, localtimestamp from dual;

SYSTIMESTAMP                                      CURRENT_TIMESTAMP                                 LOCALTIMESTAMP

------------------------------------------------- ------------------------------------------------- -------------------------------------------------

2008/03/29 15:59:37.400640 +08:00                 2008/03/29 02:59:37.400646 -05:00                 2008/03/29 02:59:37.400646