为什么可以从 DATETIME 中减去整数而不是 DATE 类型 [英] Why can integer be subtracted from DATETIME but not DATE type

问题描述

是DATETIME & 的关系吗?整数和日期 &整数一致?

Is the relationship between DATETIME & INTEGER and DATE & INTEGER consistent?

这执行得很好:

DECLARE @Yesterday DATETIME = GETDATE();
SELECT @Yesterday-1;

就像这样:

DECLARE @Yesterday DATE = GETDATE();
SELECT @Yesterday;

这个错误:

DECLARE @Yesterday DATE = GETDATE();
SELECT @Yesterday-1;

我可以安全地从 datetime 中减去 integer 类型，但不能从 date 中减去.
这种行为的原因是什么?

I can safely subtract an integer type from a datetime but not from a date.
What is the reason for this behaviour?

推荐答案

其实还是很一致的.DATETIME 是从以前版本的 sql server 继承的类型.从 2008 版开始，引入了 DATETIME2，并删除了加减整数的可能性.您仍然可以在 DATETIME 上将其作为遗留.

Actually, it is very consistent. DATETIME is a type inherited from previous editions of sql server. Since 2008 edition, DATETIME2 has been introduced, and possibility of adding/subtracting integers removed. You can still do it on DATETIME as a legacy.

DATE 和 DATETIME2 一样，也是从 2008 年开始出现的，而且这种类型的加减数字也是被禁止的.

DATE, like DATETIME2 had been around since 2008, too, and for this type adding/subtracting numbers is also prohibited.

这会给你一个错误:

DECLARE @Yesterday DATETIME2 = GETDATE();
SELECT @Yesterday-1;

所以一切都很好:)

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