trunc(date，'IW')到底是什么? [英] What exactly does trunc(date, 'IW')?

问题描述

对于我的项目，我需要在星期几和1 ... 7值之间具有绝对的数值对应关系.

For my project I need to have an absolute numerical correspondence between days of the week and 1...7 values.

您可能已经知道，天数与数字之间的关联会因地区而异，例如在德国，周一为1，周日为7，而在美国，周一为2，而周日为1.

As you probably know the association between days and numbers can vary according to the locale, for example in Germany Monday is 1 and Sunday is 7, while in US Monday is 2 while Sunday is 1.

因此，在寻找解决方案时，我发现以下代码似乎不管区域设置如何都起作用，将Monday = 1 ... Sunday = 7分配了:

So, searching for a solution, I found the following code which seems working regardless of the locale, assigning Monday=1...Sunday=7:

1 + TRUNC (date) - TRUNC (date, 'IW')

有人可以向我解释一下它是如何工作的吗?特别是我只是不明白这条指令是什么:

Can someone explain me how does it work? In particular I just can't understand what this instruction:

TRUNC (date, 'IW')

确实如此.

推荐答案

TRUNC(DATE,'IW')返回一周的第一天.对我来说，TRUNC(SYSDATE,'IW)返回星期一.今天是2月21日，星期二.从那个TRUNC(SYSDATE,'IW')减去那将是20日星期一，您将得到1(因为21-20=1).像在方程式的开头那样在该值上添加1，您将得到2，我们将其与星期二关联.

TRUNC(DATE,'IW') returns the first day of the week. For me TRUNC(SYSDATE,'IW) returns Monday. Today is Tuesday Feb 21. Subtract from that TRUNC(SYSDATE,'IW') which would be Monday the 20th, and you'll get 1 (because 21-20=1). Add 1 onto that as you do in the beginning of your equation and you get 2, which we associate with Tuesday.

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