在Oracle中使用from_tz時避免夏令時造成的異常

Oracle 中的from_tz函數，可以將一個timstamp和timzone拼成一個timestamp with timezone

SQL> select from_tz(to_timestamp('20090102','YYYYMMDD'), 'America/Sao_Paulo') from dual;

FROM_TZ(TO_TIMESTAMP('20090102
--------------------------------------------------------------------------------
02-1月 -09 12.00.00.000000000 上午 AMERICA/SAO_PAULO

SQL> select from_tz(to_timestamp('20090102','YYYYMMDD'), 'America/Sao_Paulo') from dual;
 
FROM_TZ(TO_TIMESTAMP('20090102
--------------------------------------------------------------------------------
02-1月 -09 12.00.00.000000000 上午 AMERICA/SAO_PAULO

 

但如果這個timestamp在指定的時區內不存在(比如由於夏令時，時鐘往前撥了一個小時），就會拋Exception

SQL> select from_tz(to_timestamp('20091101','YYYYMMDD'), 'America/Sao_Paulo') from dual;

select from_tz(to_timestamp('20091101','YYYYMMDD'), 'America/Sao_Paulo') from dual

ORA-01878: 在日期時間或間隔中沒有找到指定的字段

SQL> select from_tz(to_timestamp('20091101','YYYYMMDD'), 'America/Sao_Paulo') from dual;
 
select from_tz(to_timestamp('20091101','YYYYMMDD'), 'America/Sao_Paulo') from dual
 
ORA-01878: 在日期時間或間隔中沒有找到指定的字段

 解決辦法嘛，先取出時區的offset，用其構建好timestamp with timezone後再轉回指定的時區就好了

SQL> select from_tz(to_timestamp('20091101','YYYYMMDD'), tz_offset('America/Sao_Paulo')) at TIME ZONE 'America/Sao_Paulo' from dual;

FROM_TZ(TO_TIMESTAMP('20091101
--------------------------------------------------------------------------------
31-10月-09 11.00.00.000000000 下午 AMERICA/SAO_PAULO