Question

我正在寻找一种使用表中定义的日期按间隔（例如，每30分钟）对数据进行分组的方法，因此我需要将该日期时间转换为毫秒，以便可以将其除以所需的间隔就像在这个查询中一样

SELECT FLOOR(UNIX_TIMESTAMP(timestamp)/(15 * 60 * 1000)) AS timekey
FROM table
GROUP BY timekey;

此查询在SQL Server上运行完美，但在notifyix上却给我错误

Routine (unix_timestamp) can not be resolved.

由于未在IBM Informix服务器中定义。因此，我需要一种直接的方法来从IBM notifyix服务器中的timestamp DATETIME YEAR TO FRACTION（3）列获取纪元unix时间，例如SQL Server中的“ UNIX_TIMESTAMP”。

Answer 1

如果timestamp列的类型为DATETIME YEAR TO SECOND或类似类型，则可以将其转换为自Unix纪元（也称为1970-01-01 00）以来的DECIMAL（18,5）秒数： 00：00Z（UTC;时区偏移+00：00），例如以下步骤：

{
#   "@(#)$Id: tounixtime.spl,v 1.6 2002/09/25 18:10:48 jleffler Exp $"
#
# Stored procedure TO_UNIX_TIME written by Jonathan Leffler (previously
# jleffler@informix.com and now jleffler@us.ibm.com).  Includes fix for
# bug reported by Tsutomu Ogiwara <Tsutomu.Ogiwara@ctc-g.co.jp> on
# 2001-07-13.  Previous version used DATETIME(0) SECOND TO SECOND
# instead of DATETIME(0:0:0) HOUR TO SECOND, and when the calculation
# extended the shorter constant to DATETIME HOUR TO SECOND, it added the
# current hour and minute fields, as documented in the Informix Guide to
# SQL: Syntax manual under EXTEND in the section on 'Expression'.
# Amended 2002-08-23 to handle 'eternity' and annotated more thoroughly.
# Amended 2002-09-25 to handle fractional seconds, as companion to the
# new stored procedure FROM_UNIX_TIME().
#
# If you run this procedure with no arguments (use the default), you
# need to worry about the time zone the database server is using because
# the value of CURRENT is determined by that, and you need to compensate
# for it if you are using a different time zone.
#
# Note that this version works for dates after 2001-09-09 when the
# interval between 1970-01-01 00:00:00+00:00 and current exceeds the
# range of INTERVAL SECOND(9) TO SECOND.  Returning DECIMAL(18,5) allows
# it to work for all valid datetime values including fractional seconds.
# In the UTC time zone, the 'Unix time' of 9999-12-31 23:59:59 is
# 253402300799 (12 digits); the equivalent for 0001-01-01 00:00:00 is
# -62135596800 (11 digits).  Both these values are unrepresentable in
# 32-bit integers, of course, so most Unix systems won't handle this
# range, and the so-called 'Proleptic Gregorian Calendar' used to
# calculate the dates ignores locale-dependent details such as the loss
# of days that occurred during the switch between the Julian and
# Gregorian calendar, but those are minutiae that most people can ignore
# most of the time.
}

CREATE PROCEDURE to_unix_time(d DATETIME YEAR TO FRACTION(5)
                                DEFAULT CURRENT YEAR TO FRACTION(5))
            RETURNING DECIMAL(18,5);
    DEFINE n DECIMAL(18,5);
    DEFINE i1 INTERVAL DAY(9) TO DAY;
    DEFINE i2 INTERVAL SECOND(6) TO FRACTION(5);
    DEFINE s1 CHAR(15);
    DEFINE s2 CHAR(15);
    LET i1 = EXTEND(d, YEAR TO DAY) - DATETIME(1970-01-01) YEAR TO DAY;
    LET s1 = i1;
    LET i2 = EXTEND(d, HOUR TO FRACTION(5)) -
                DATETIME(00:00:00.00000) HOUR TO FRACTION(5);
    LET s2 = i2;
    LET n = s1 * (24 * 60 * 60) + s2;
    RETURN n;
END PROCEDURE;

一些有关电子邮件地址的评论不再有效-自从我写这篇文章以来的十五年里，情况发生了变化。

Informix FROM_UNIXTIME的替代方法

1 个答案: