问题
I have a timestamp datatype in database with format 24-JuL-11 10.45.00.000000000 AM and want to get it converted into unix timestamp, how can I get it?
回答1:
This question is pretty much the inverse of Convert Unixtime to Datetime SQL (Oracle)
As Justin Cave says:
There are no built-in functions. But it's relatively easy to write one. Since a Unix timestamp is the number of seconds since January 1, 1970
As subtracting one date from another date results in the number of days between them you can do something like:
create or replace function date_to_unix_ts( PDate in date ) return number is
l_unix_ts number;
begin
l_unix_ts := ( PDate - date '1970-01-01' ) * 60 * 60 * 24;
return l_unix_ts;
end;
As its in seconds since 1970 the number of fractional seconds is immaterial. You can still call it with a timestamp data-type though...
SQL> select date_to_unix_ts(systimestamp) from dual;
DATE_TO_UNIX_TS(SYSTIMESTAMP)
-----------------------------
1345801660
In response to your comment, I'm sorry but I don't see that behaviour:
SQL> with the_dates as (
2 select to_date('08-mar-12 01:00:00 am', 'dd-mon-yy hh:mi:ss am') as dt
3 from dual
4 union all
5 select to_date('08-mar-12', 'dd-mon-yy')
6 from dual )
7 select date_to_unix_ts(dt)
8 from the_dates
9 ;
DATE_TO_UNIX_TS(DT)
-------------------
1331168400
1331164800
SQL>
There's 3,600 seconds difference, i.e. 1 hour.
回答2:
I realize an answer has already been accepted, but I think it should be made clear that the function in that answer doesn't consider the passed in date's time zone offset. A proper Unix timestamp should be calculated at GMT (+0). Oracle's to_date function assumes the passed in date is in the local time zone unless otherwise specified. This problem is exacerbated by the fact that Daylight Saving Time is a real thing. I over came this problem with the following function:
create or replace
function unix_time_from_date
(
in_date in date,
in_src_tz in varchar2 default 'America/New_York'
)
return integer
as
ut integer := 0;
tz varchar2(8) := '';
tz_date timestamp with time zone;
tz_stmt varchar2(255);
begin
/**
* This function is used to convert an Oracle DATE (local timezone) to a Unix timestamp (UTC).
*
* @author James Sumners
* @date 01 February 2012
*
* @param in_date An Oracle DATE to convert. It is assumed that this date will be in the local timezone.
* @param in_src_tz Indicates the time zone of the in_date parameter.
*
* @return integer
*/
-- Get the current timezone abbreviation (stupid DST)
tz_stmt := 'select systimestamp at time zone ''' || in_src_tz || ''' from dual';
execute immediate tz_stmt into tz_date;
select
extract(timezone_abbr from tz_date)
into tz
from dual;
-- Get the Unix timestamp
select
(new_time(in_date, tz, 'GMT') - to_date('01-JAN-1970', 'DD-MM-YYYY')) * (86400)
into ut
from dual;
return ut;
end unix_time_from_date;
I have some companion functions, unix_time and unix_time_to_date, available at http://jrfom.com/2012/02/10/oracle-and-unix-timestamps-revisited/. I can't believe Oracle has made it all the way to 11g without implementing these.
回答3:
for date:
FUNCTION date_to_unix (p_date date,in_src_tz in varchar2 default 'Europe/Kiev') return number is
begin
return round((cast((FROM_TZ(CAST(p_date as timestamp), in_src_tz) at time zone 'GMT') as date)-TO_DATE('01.01.1970','dd.mm.yyyy'))*(24*60*60));
end;
for timestamp:
FUNCTION timestamp_to_unix (p_time timestamp,in_src_tz in varchar2 default 'Europe/Kiev') return number is
begin
return round((cast((FROM_TZ(p_time, in_src_tz) at time zone 'GMT') as date)-TO_DATE('01.01.1970','dd.mm.yyyy'))*(24*60*60));
end;
回答4:
I'm using following method, which differs a little from other answers in that it uses sessiontimezone() function to properly get date
select
(
cast((FROM_TZ(CAST(in_date as timestamp), sessiontimezone) at time zone 'GMT') as date) -- in_date cast do GMT
-
TO_DATE('01.01.1970','dd.mm.yyyy') -- minus unix start date
)
* 86400000 -- times miliseconds in day
from dual;
回答5:
This was what I came up with:
select substr(extract(day from (n.origstamp - timestamp '1970-01-01 00:00:00')) * 24 * 60 * 60 +
extract(hour from (n.origstamp - timestamp '1970-01-01 00:00:00')) * 60 * 60 +
extract(minute from (n.origstamp - timestamp '1970-01-01 00:00:00')) * 60 +
trunc(extract(second from (n.origstamp - timestamp '1970-01-01 00:00:00')),0),0,15) TimeStamp
from tablename;
FWIW
回答6:
SELECT (SYSDATE - TO_DATE('01-01-1970 00:00:00', 'DD-MM-YYYY HH24:MI:SS')) * 24 * 60 * 60 * 1000 FROM DUAL
回答7:
For conversion between Oracle time and Unix times I use these functions.
They consider your current timezone. You should also add DETERMINISTIC keyword, for example if you like to use such function in a function-based index. Conversion between DATE and TIMESTAMP should be done implicitly by Oracle.
FUNCTION Timestamp2UnixTime(theTimestamp IN TIMESTAMP, timezone IN VARCHAR2 DEFAULT SESSIONTIMEZONE) RETURN NUMBER DETERMINISTIC IS
timestampUTC TIMESTAMP;
theInterval INTERVAL DAY(9) TO SECOND;
epoche NUMBER;
BEGIN
timestampUTC := FROM_TZ(theTimestamp, timezone) AT TIME ZONE 'UTC';
theInterval := TO_DSINTERVAL(timestampUTC - TIMESTAMP '1970-01-01 00:00:00');
epoche := EXTRACT(DAY FROM theInterval)*24*60*60
+ EXTRACT(HOUR FROM theInterval)*60*60
+ EXTRACT(MINUTE FROM theInterval)*60
+ EXTRACT(SECOND FROM theInterval);
RETURN ROUND(epoche);
END Timestamp2UnixTime;
FUNCTION UnixTime2Timestamp(UnixTime IN NUMBER) RETURN TIMESTAMP DETERMINISTIC IS
BEGIN
RETURN (TIMESTAMP '1970-01-01 00:00:00 UTC' + UnixTime * INTERVAL '1' SECOND) AT LOCAL;
END UnixTime2Timestamp;
回答8:
SELECT
to_char(sysdate, 'YYYY/MM/DD HH24:MI:SS') dt,
round((sysdate - to_date('19700101 000000', 'YYYYMMDD HH24MISS'))*86400) as udt
FROM dual;
来源：https://stackoverflow.com/questions/12105691/convert-timestamp-datatype-into-unix-timestamp-oracle