sql - 如何在SQL中选择一个月的第一天？(How can I select the first day of a month in SQL?)

Question

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

(我只需要选择给定datetime变量的月份的第一天。)

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

(我知道使用这种代码非常容易：)

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

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

(但这不是很优雅，也可能不是很快。)

Is there a better way to do this?

(有一个更好的方法吗？)

I'm using SQL Server 2008.

(我正在使用SQL Server 2008。)

  ask by Brann translate from so

Answer 1

SELECT DATEADD(month, DATEDIFF(month, 0, @mydate), 0) AS StartOfMonth