Oracle Convert TIMESTAMP with Timezone to DATE

问题:

I have DB with timezone +04:00 (Europe/Moscow) and need to convert a string in format YYYY-MM-DD"T"HH24:MI:SSTZH:TZM to DATE data type in Oracle 11g.

In other words, I have a string 2013-11-08T10:11:31+02:00 and I want to convert it to DATE data type (in local DB timezone +04:00 (Europe/Moscow)).

For string 2013-11-08T10:11:31+02:00 my desired transformation should return DATE data type with date 2013-11-08 12:11:31 (i.e. with local timezone transformation of time to +04:00 (Europe/Moscow)). Timezone of string may be different and +02:00 in string above is just example.

I tried to do this with TIMESTAMP data type, but no success with time zone transformation.

回答1:

to_timestamp_tz() function with at time zone clause can be used to convert your string literal to a value of timestamp with time zone data type:

SQL> with t1(tm) as(
  2    select '2013-11-08T10:11:31+02:00' from dual
  3  )
  4  select to_timestamp_tz(tm, 'yyyy-mm-dd"T"hh24:mi:ss TZH:TZM')
  5           at time zone '+4:00'         as this_way
  6       , to_timestamp_tz(tm, 'yyyy-mm-dd"T"hh24:mi:ss TZH:TZM')
  7           at time zone 'Europe/Moscow' as or_this_way
  8    from t1
  9  /

Result:

THIS_WAY                            OR_THIS_WAY
----------------------------------------------------------------------------
2013-11-08 12.11.31 PM +04:00       2013-11-08 12.11.31 PM EUROPE/MOSCOW

And then, we use cast() function to produce a value of date data type:

with t1(tm) as(
  select '2013-11-08T10:11:31+02:00' from dual
)
select cast(to_timestamp_tz(tm, 'yyyy-mm-dd"T"hh24:mi:ss TZH:TZM') 
         at time zone '+4:00' as date)   as this_way  
     , cast(to_timestamp_tz(tm, 'yyyy-mm-dd"T"hh24:mi:ss TZH:TZM') 
         at time zone 'Europe/Moscow' as date) as or_this_way
  from t1

This_Way             Or_This_Way 
------------------------------------------
2013-11-08 12:11:31  2013-11-08 12:11:31 

Find out more about at time zone clause and to_timestamp_tz() function.

回答2:

SELECT
CAST((FROM_TZ(CAST(timezonefield AS TIMESTAMP),'GMT') AT TIME ZONE 'CET') AS DATE) 
FROM table;

Converts a timestamp in GMT to date in Central European time