DATEPART（年，...）与年度（...）(Datepart(year, …) vs. Year

什么是使用了另一种在以下的优点：

DATEPART(YEAR, GETDATE())

而不是：

YEAR(GETDATE())

是否存在性能差异？如果是这样，哪一个是最快的？

Answer 1:

其实-使用YEAR(..)最好是对我来说，因为它被认为是一个确定性的功能，因此，如果我用这个在计算列定义

ALTER TABLE dbo.MyTable
ADD YearOfDate AS YEAR(SomeDateColumn)

我可以让这个专栏坚持（并将其存储到表）：

ALTER TABLE dbo.MyTable
ADD YearOfDate AS YEAR(SomeDateColumn) PERSISTED

这并不适用于工作DATEPART(YEAR, SomeDateColumn) -只注意到这个启发式不要问我为什么）。

这同样适用于MONTH(SomeDate)与DATEPART(MONTH, SomeDate)

如果您有需要从基础上的日期（如月份和年份选择表SalesDate再有一个月，年持久化计算列（和索引他们）什么的），可以是一个巨大的性能提升。

Answer 2:

没有区别。在执行计划都被转换为datepart(year,getdate())

这是SQL Server 2005中，2008年和2012年真实的。

select datepart(year, getdate())
from (select 1 x) x

select year(getdate())
from (select 1 x) x

执行计划。

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