TSQL只需要返回一个月的最后一天,如何删除年,月和时间？

Question

我正在T-SQL中编写一个函数,无论日期输入如何,都会返回该月的最后一天.

这是我的代码:

Alter Function dbo.FN_Get_Last_Day_in_Month2
(@FN_InputDt    Datetime)
Returns smalldatetime
as 
Begin

Declare @Result  smalldatetime
Set    @Result =

       case when @FN_InputDt <> 01-01-1900 then 
       DATEADD(m, DATEDIFF(M, 0,@FN_InputDt)+1, -1)
       Else 0 End

Return @Result

End 

代码无法正常工作,这是一个显示不良行为的测试:

SELECT dbo.fn_get_last_day_in_month (07-05-2010)

这是(不正确的)结果:

2010-07-31 00:00:00

Answer 1

什么是07-05-2010 ... 5月7日或7月5日？您需要使用安全日期格式,请参阅为SQL Server设置标准DateFormat

示例来自如何查找年,月等的第一天和最后一天

DECLARE @d DATETIME
SET @d = '20100705'  -- notice ISO format

SELECT
    DATEADD(yy, DATEDIFF(yy, 0, @d), 0) AS FirstDayOfYear,
    DATEADD(yy, DATEDIFF(yy, 0, @d)+1, -1) AS LastDayOfYear,
    DATEADD(qq, DATEDIFF(qq, 0, @d), 0) AS FirstDayOfQuarter,
    DATEADD(qq, DATEDIFF(qq, 0, @d)+1, -1) AS LastDayOfQuarter,
    DATEADD(mm, DATEDIFF(mm, 0, @d), 0) AS FirstDayOfMonth,
    DATEADD(mm, DATEDIFF(mm, 0, @d)+1, -1) AS LastDayOfMonth,
    @d - DATEDIFF(dd, @@DATEFIRST - 1, @d) % 7 AS FirstDayOfWeek,
    @d - DATEDIFF(dd, @@DATEFIRST - 1, @d) % 7 + 6 AS LastDayOfWeek

仅适用于日使用日或日期部分

 select DAY(getdate()),
     DATEPART(dd,GETDATE())