Oracle:从datetime中减去毫秒 [英] Oracle: subtract millisecond from a datetime
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问题描述
我以为这很简单,但不是这样。
I thought it was really simple but it isn't.
SELECT TO_TIMESTAMP('10/08/2012','DD/MM/YYYY')
- 1/(24*50*60*1000) data
FROM dual;
它根本不起作用。
其他详细信息:
SELECT TO_TIMESTAMP('10/08/2012','DD/MM/YYYY') -
NUMTODSINTERVAL(1/(24*50*60*1000),'HOUR') data
FROM dual;
不工作。
右边似乎是
SELECT TO_TIMESTAMP('10/08/2012','DD/MM/YYYY') -
NUMTODSINTERVAL(1/(24*25*60*1000),'HOUR') data
FROM dual;
为什么?如何工作?
推荐答案
为了添加或减少一段时间,以文字形式表达,您可以使用INTERVAL。
For adding or subtracting an amount of time expressed as a literal you can use INTERVAL.
SELECT TO_TIMESTAMP('10/08/2012','DD/MM/YYYY')
- INTERVAL '0.001' SECOND
FROM dual;
现在还有标准的方式来表达日期和时间文字,并避免使用各种数据库转换功能。
As well there are now standard ways to express date and time literals and avoid the use of various database specific conversion functions.
SELECT TIMESTAMP '2012-10-08 00:00:00'
- INTERVAL '0.001' SECOND DATA
FROM dual;
对于您的原始问题,一天中的一部分时间将以小数天数存储。所以一秒钟是:
For your original question the time part of a day is stored in fractional days. So one second is:
1 / (hours in day * minutes in hour * seconds in a minute)
除以1000获得毫秒。
Divide by 1000 to get milliseconds.
1 / (24 * 60 * 60 * 1000)
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