Oracle数据库时间戳与时区的时间戳

Question

Need help in inserting the data from timestamp , to timestamp with zone.

create table foo ( tswtz TIMESTAMP WITH TIME ZONE);

SQL:>insert into foo values(systimestamp)

TSWTZ                                 
---------------------------------------
09-08-16 11:39:21.199780000 AM +05:30 

create table foo1 (test_dt timestamp)

insert into foo1 values(systimestamp)
TEST_DT                        
--------------------------------
09-08-16 11:40:55.242754000 AM 

Now , there is a scenario, where i need to insert the values of foo1 to foo . I have used the below command,

insert into foo (TSWTZ)  (select CAST(TEST_DT AS TIMESTAMP WITH TIME ZONE)  from foo1)

The select value displayed it as

09-08-16 11:40:55.242754000 AM ASIA/CALCUTTA

But it should display it as

09-08-16 11:40:55.242754000 AM +05:30.

Can you please help me on how to do that, without alter command ?

Answer 1

You need to alter your NLS parameters to get the result. Please read the oracle documentation as well [ https://docs.oracle.com/cd/B19306_01/server.102/b14225/ch4datetime.htm][1]

Try setting:

 NLS_TIMESTAMP_TZ_FORMAT = DD-MON-RR HH.MI.SSXFF AM TZR
and NLS_TIMESTAMP_FORMAT = DD-MON-RR HH.MI.SSXFF AM
and NLS_TIME_TZ_FORMAT = HH.MI.SSXFF AM TZR
and NLS_TIME_FORMAT =   HH.MI.SSXFF AM

Answer 2

Function SYSTIMESTAMP returns current time in time zone of your database server operating system, in your case +05:30 .

When you cast from TIMESTAMP (without any time zone information) to TIMESTAMP WITH TIME ZONE then Oracle takes your SESSIONTIMEZONE - unless you specify the time zone explicitly.

Obviously in your case the SESSIONTIMEZONE is set to Asia/Calcutta .

In order to get desired result you can do either

ALTER SESSION SET TIME_ZONE = '+05:30';

or

SELECT CAST((TEST_DT AT TIME ZONE '+05:30') AS TIMESTAMP WITH TIME ZONE) 
FROM ...

Note, time zone Asia/Calcutta is different than +05:30 , although the offset is the same. Region names like Asia/Calcutta considers daylight saving times (which does not apply for Asia/Calcutta), UTC offsets like +05:30 do not consider daylight saving times.