Oracleでミリ秒単位のタイムスタンプを日付に変換する方法

エポックからのミリ秒から日付に変換する必要がある場合は、次のようにします。

SELECT TIMESTAMP '1970-01-01 00:00:00.000'
         + NUMTODSINTERVAL( 1483228800000 / 1000, 'SECOND' )
         AS TIME
FROM   DUAL

どの出力：

TIME
-----------------------
2017-01-01 00:00:00.000

年月が必要な場合は、TRUNC( timestamp, 'MM' )を使用しますまたはTO_CHAR( timestamp, 'YYYY-MM' ) 。

うるう秒を処理する必要がある場合は、これを考慮してエポック時間を調整するユーティリティパッケージを作成できます。

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;

次に、次のことができます：

SELECT TIME_UTILS.milliseconds_epoch_to_ts(
         in_milliseconds => 1483228800000,
         in_epoch        => TIMESTAMP '1970-00-00 00:00:00.000'
       ) AS time
FROM DUAL;

そして、出力を取得します：

TIME
-----------------------
2016-12-31 23:59:33.000

注：新しいうるう秒が提案された場合は、パッケージを最新の状態に保つ必要があります。

更新：

SELECT COUNT(*) "EVENTS",
       TRUNC(
         TIMESTAMP '1970-01-01 00:00:00.000'
           + NUMTODSINTERVAL( MSSTAMP / 1000, 'SECOND' ),
         'MM'
       ) "FINISHED_MONTH"
FROM   DB_TABLE
WHERE  MSSTAMP < 1483228800000
AND    STATUS = 'FINISHED'
GROUP BY
       TRUNC(
         TIMESTAMP '1970-01-01 00:00:00.000'
           + NUMTODSINTERVAL( MSSTAMP / 1000, 'SECOND' ),
         'MM'
       );