MS SQL Server Scalar Valued Function for Difference Between Two Dates

-- =============================================
-- Author: <Author,,Kapil Dev Mehra>
-- Create date: <Create Date, ,30/12/2016>
-- Description: <Description, ,Get difference between two dates>
-- =============================================
CREATE FUNCTION [dbo].[funGetDiffDates]
(
@NewDate nvarchar(10),
@OldDate nvarchar(10)
)
RETURNS nvarchar(50)
AS
BEGIN
DECLARE @Diff_Day int, @Diff_Month int, @Diff_Year int
DECLARE @OldDate_Day int, @OldDate_Month int, @OldDate_Year int
DECLARE @NewDate_Day int, @NewDate_Month int, @NewDate_Year int
SELECT @OldDate_Day = SUBSTRING(@OldDate,1,2), @OldDate_Month = SUBSTRING(@OldDate,4,2), @OldDate_Year = SUBSTRING(@OldDate,7,4)
SELECT @NewDate_Day = SUBSTRING(@NewDate,1,2), @NewDate_Month = SUBSTRING(@NewDate,4,2), @NewDate_Year = SUBSTRING(@NewDate,7,4)

IF @OldDate_Day > @NewDate_Day
BEGIN
SET @NewDate_Month = @NewDate_Month - 1
SET @NewDate_Day = @NewDate_Day + 30

END
SET @Diff_Day = @NewDate_Day - @OldDate_Day

IF @OldDate_Month > @NewDate_Month
BEGIN
SET @NewDate_Year = @NewDate_Year - 1
SET @NewDate_Month = @NewDate_Month + 12
END
SET @Diff_Month = @NewDate_Month - @OldDate_Month
SET @Diff_Year = @NewDate_Year - @OldDate_Year

DECLARE @Return_Year nvarchar(15), @Return_Month nvarchar(15), @Return_Day nvarchar(15)
IF @Diff_Year > 1
SET @Return_Year = CONVERT(nvarchar, @Diff_Year) + ' Years, '
ELSE
SET @Return_Year = CONVERT(nvarchar, @Diff_Year) + ' Year, '

IF @Diff_Month > 1
SET @Return_Month = CONVERT(nvarchar, @Diff_Month) + ' Months, '
ELSE
SET @Return_Month = CONVERT(nvarchar, @Diff_Month) + ' Month, '

IF @Diff_Day > 1
SET @Return_Day = CONVERT(nvarchar, @Diff_Day) + ' Days'
ELSE
SET @Return_Day = CONVERT(nvarchar, @Diff_Day) + ' Day'

RETURN @Return_Year + @Return_Month + @Return_Day
END


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