獲取指定日期所屬年份的第一天日期或最後一天日期

寫了2個自定義函數，獲取指定日期所在年份的第一天日期或最後一天的日期：

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:      Insus.NET
-- Create date: 2019-05-09
-- Update date: 2019-05-09
-- Description: 獲取指定日期所屬年份的第一天日期
-- =============================================
CREATE FUNCTION [dbo].[svf_FirstDateOfTheYear]
( 
    @TheYear DATETIME 
)
RETURNS DATETIME
AS
BEGIN
    RETURN  DATEADD(YEAR,DATEDIFF(YEAR,0,@TheYear),0)  
END

GO

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author:      Insus.NET
-- Create date: 2019-05-09
-- Update date: 2019-05-09
-- Description: 獲取指定日期所屬年份的最後一天日期
-- =============================================
CREATE FUNCTION [dbo].[svf_LastDateOfTheYear]
( 
    @TheYear DATETIME 
)
RETURNS DATETIME
AS
BEGIN
    RETURN DATEADD(DAY,-1,DATEADD(YEAR,DATEDIFF(YEAR,0,@TheYear) + 1,0))
END
GO

舉例說明：