将字符串转换为 oracle sql 时间戳 Mon Aug 19 2019 08:21:48 GMT-0700 (PDT)

Question

Greeting Community.

I saw similar examples in Java but how do we do it it SQL in particular Oracle. For now I just do this which it works because we are in PDT timezone.

-Thx for the help!

with xx as ( 
select replace('Mon Aug 19 2019 08:21:48 GMT-0700 (PDT)',' GMT-0700 (PDT)','') as dt from dual

)

select to_date(dt,'DY MON DD YYYY HH24:MI:SS') from xx

Answer 1

The input is a timestamp with time zone. It has redundant information about the time zone; some of that must be stripped away. For example, if you choose to trust PDT and ignore the GMT offset, you could do something like this:

with xx as ( 
select regexp_replace('Mon Aug 19 2019 08:21:48 GMT-0700 (PDT)','GMT-\d{4} \(|\)') 
       as str_ts_with_tz 
from   dual
)
select to_timestamp_tz(str_ts_with_tz,'Dy Mon DD YYYY HH24:MI:SS TZD') 
       as oracle_ts_with_tz 
from   xx
;



ORACLE_TS_WITH_TZ                      
---------------------------------------
2019-08-19 08:21:48 America/Los_Angeles

Note that the resulting data type is timestamp with time zone . You can further cast this as timestamp or as date (simply discarding the time zone information) if needed; this is a simple operation, internal to Oracle. But that will lose information; think twice before you do that.

Note also that the timestamp is presented in a different format in my output, compared to your input. This is because my NLS_TIMESTAMP_TZ_FORMAT is 'yyyy-mm-dd hh24:mi:ss tzr' .

If you are wondering why you must make a choice (which, then, means "why you need to delete part of the input string first") regarding the time zone information: PDT is simply not the same as GMT-0700. It may be that in summer, but not in winter. Oracle won't accept such self-contradicting nonsense as input to its functions. Either it's GMT-0700 or it's PDT, it can't be both. And, you can't just use REPLACE (not easily, anyway), because what must be replaced may have variable characters in it.