Difference Between Timestamps in Milliseconds in O

Question

I have table test1 and have one column DOJ with timestamp datatype having few records as shown below. Here i need the difference im milliseconds between doj and systimestamp.

SELECT DOJ FROM TEST1; 
DOJ 
---------------------------- 
21-MAR-14 09.25.34.514526000 
21-MAR-14 09.25.34.520345000 
22-MAR-14 09.25.34.523144000 
22-MAR-14 09.25.34.527770000 
23-MAR-14 09.25.34.532482000 
23-MAR-14 09.25.34.535603000 
24-MAR-14 09.25.34.538556000 
24-MAR-14 09.25.34.541729000 

SELECT SYSTIMESTAMP FROM DUAL; 
SYSTIMESTAMP 
-------------- 
24-MAR-14 09.48.10.251556000 +00:00 

Can some one please help me with this.

Answer 1

If you need to handle leap seconds then you can create a utility package that will adjust the epoch time to account for this:

CREATE OR REPLACE PACKAGE time_utils
IS
  FUNCTION milliseconds_since_epoch(
    in_datetime  IN TIMESTAMP,
    in_epoch     IN TIMESTAMP DEFAULT TIMESTAMP '1970-01-01 00:00:00'
  ) RETURN NUMBER;

  FUNCTION milliseconds_epoch_to_ts (
    in_milliseconds IN NUMBER,
    in_epoch        IN TIMESTAMP DEFAULT TIMESTAMP '1970-01-01 00:00:00'
  ) RETURN TIMESTAMP;
END;
/
SHOW ERRORS;

CREATE OR REPLACE PACKAGE BODY time_utils
IS
  -- List of the seconds immediately following leap seconds:
  leap_seconds CONSTANT SYS.ODCIDATELIST := SYS.ODCIDATELIST(
      DATE '1972-07-01',
      DATE '1973-01-01',
      DATE '1974-01-01',
      DATE '1975-01-01',
      DATE '1976-01-01',
      DATE '1977-01-01',
      DATE '1978-01-01',
      DATE '1979-01-01',
      DATE '1980-01-01',
      DATE '1981-07-01',
      DATE '1982-07-01',
      DATE '1983-07-01',
      DATE '1985-07-01',
      DATE '1988-01-01',
      DATE '1990-01-01',
      DATE '1991-01-01',
      DATE '1992-07-01',
      DATE '1993-07-01',
      DATE '1994-07-01',
      DATE '1996-01-01',
      DATE '1997-07-01',
      DATE '1999-01-01',
      DATE '2006-01-01',
      DATE '2009-01-01',
      DATE '2012-07-01',
      DATE '2015-07-01',
      DATE '2016-01-01'
    );

  HOURS_PER_DAY           CONSTANT BINARY_INTEGER := 24;
  MINUTES_PER_HOUR        CONSTANT BINARY_INTEGER := 60;
  SECONDS_PER_MINUTE      CONSTANT BINARY_INTEGER := 60;
  MILLISECONDS_PER_SECOND CONSTANT BINARY_INTEGER := 1000;

  MINUTES_PER_DAY         CONSTANT BINARY_INTEGER := HOURS_PER_DAY   * MINUTES_PER_HOUR;
  SECONDS_PER_DAY         CONSTANT BINARY_INTEGER := MINUTES_PER_DAY * SECONDS_PER_MINUTE;

  MILLISECONDS_PER_MINUTE CONSTANT BINARY_INTEGER := SECONDS_PER_MINUTE * MILLISECONDS_PER_SECOND;
  MILLISECONDS_PER_HOUR   CONSTANT BINARY_INTEGER := MINUTES_PER_HOUR   * MILLISECONDS_PER_MINUTE;
  MILLISECONDS_PER_DAY    CONSTANT BINARY_INTEGER := HOURS_PER_DAY      * MILLISECONDS_PER_HOUR;

  FUNCTION milliseconds_since_epoch(
    in_datetime  IN TIMESTAMP,
    in_epoch     IN TIMESTAMP DEFAULT TIMESTAMP '1970-01-01 00:00:00'
  ) RETURN NUMBER
  IS
    p_leap_milliseconds BINARY_INTEGER := 0;
    p_diff              INTERVAL DAY(9) TO SECOND(3);
  BEGIN
    IF in_datetime IS NULL OR in_epoch IS NULL THEN
      RETURN NULL;
    END IF;

    p_diff := in_datetime - in_epoch;

    IF in_datetime >= in_epoch THEN
      FOR i IN 1 .. leap_seconds.COUNT LOOP
        EXIT WHEN in_datetime < leap_seconds(i);
        IF in_epoch < leap_seconds(i) THEN
          p_leap_milliseconds := p_leap_milliseconds + MILLISECONDS_PER_SECOND;
        END IF;
      END LOOP;
    ELSE
      FOR i IN REVERSE 1 .. leap_seconds.COUNT LOOP
        EXIT WHEN in_datetime > leap_seconds(i);
        IF in_epoch > leap_seconds(i) THEN
          p_leap_milliseconds := p_leap_milliseconds - MILLISECONDS_PER_SECOND;
        END IF;
      END LOOP;
    END IF;

    RETURN   MILLISECONDS_PER_SECOND * EXTRACT( SECOND FROM p_diff )
           + MILLISECONDS_PER_MINUTE * EXTRACT( MINUTE FROM p_diff )
           + MILLISECONDS_PER_HOUR   * EXTRACT( HOUR   FROM p_diff )
           + MILLISECONDS_PER_DAY    * EXTRACT( DAY    FROM p_diff )
           + p_leap_milliseconds;
  END milliseconds_since_epoch;

  FUNCTION milliseconds_epoch_to_ts(
    in_milliseconds IN NUMBER,
    in_epoch        IN TIMESTAMP DEFAULT TIMESTAMP '1970-01-01 00:00:00'
  ) RETURN TIMESTAMP
  IS
    p_datetime TIMESTAMP;
  BEGIN
    IF in_milliseconds IS NULL OR in_epoch IS NULL THEN
      RETURN NULL;
    END IF;

    p_datetime := in_epoch
        + NUMTODSINTERVAL( in_milliseconds / MILLISECONDS_PER_SECOND, 'SECOND' );

    IF p_datetime >= in_epoch THEN
      FOR i IN 1 .. leap_seconds.COUNT LOOP
        EXIT WHEN p_datetime < leap_seconds(i);
        IF in_epoch < leap_seconds(i) THEN
          p_datetime := p_datetime - INTERVAL '1' SECOND;
        END IF;
      END LOOP;
    ELSE
      FOR i IN REVERSE 1 .. leap_seconds.COUNT LOOP
        EXIT WHEN p_datetime > leap_seconds(i);
        IF in_epoch > leap_seconds(i) THEN
          p_datetime := p_datetime + INTERVAL '1' SECOND;
        END IF;
      END LOOP;
    END IF;

    RETURN p_datetime;
  END milliseconds_epoch_to_ts;
END;
/
SHOW ERRORS;

Then you can do:

SELECT TIME_UTILS.MILLISECONDS_SINCE_EPOCH(
         in_datetime => TIMESTAMP '1974-01-01 00:00:00.000',
         in_epoch    => TIMESTAMP '1973-12-31 23:59:59.999'
       ) AS diff
FROM DUAL;

And get the output:

DIFF
----
1001

Note: you will need to keep the package up-to-date when new leap-seconds are proposed.

Answer 2

select
  extract(second from systimestamp - doj) * 1000
from
  test1;

Answer 3

Expanding René's answer a bit, if you want the total milliseconds then you need to extract and combine all of the elements from the interval that's produced by subtracting one timestamp from another:

select doj, systimestamp - doj,
  trunc(1000 * (extract(second from systimestamp - doj)
    + 60 * (extract(minute from systimestamp - doj)
      + 60 * (extract(hour from systimestamp - doj)
        + 24 * (extract(day from systimestamp - doj) ))))) as milliseconds
from test1;

DOJ                          SYSTIMESTAMP-DOJ     MILLISECONDS
---------------------------- ---------------- ----------------
21-MAR-14 09.25.34.514526000 3 2:9:8.785713          266948785 
21-MAR-14 09.25.34.520345000 3 2:9:8.779894          266948779 
22-MAR-14 09.25.34.523144000 2 2:9:8.777095          180548777 
22-MAR-14 09.25.34.527770000 2 2:9:8.772469          180548772 
23-MAR-14 09.25.34.532482000 1 2:9:8.767757           94148767 
23-MAR-14 09.25.34.535603000 1 2:9:8.764636           94148764 
24-MAR-14 09.25.34.538556000 0 2:9:8.761683            7748761 
24-MAR-14 09.25.34.541729000 0 2:9:8.75851             7748758 

SQL Fiddle, including the Unix epoch date for comparison, though you'd need to adjust that for your server time zone.