如何在 SQL 中选择一个月的第一天?

2021-12-01 00:00:00 datetime sql tsql sql-server-2008 sql-server

我只需要选择给定 DateTime 变量的月份的第一天.

I just need to select the first day of the month of a given DateTime variable.

我知道使用这种代码很容易做到:

I know it's quite easy to do using this kind of code:

select CAST(CAST(YEAR(@mydate) AS VARCHAR(4)) + '/' + CAST(MONTH(@mydate) AS VARCHAR(2)) + '/01' AS DATETIME)

但不幸的是，这不是很优雅，也不是很快.

But unfortunately, this is not very elegant, and not very fast either.

有没有更好的方法来做到这一点?我使用的是 SQL Server 2008.

Is there a better way to do this? I'm using SQL Server 2008.

推荐答案

除了以上所有答案，还有一种基于 sql 2012

In addition to all the above answer, a way based on a function introduced in sql 2012

SELECT DATEFROMPARTS(YEAR(@mydate),MONTH(@mydate),1)

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