GP Show the earnings of each product with comparative sales performance from previous year

Declare
@CurrentYear_StartDate As DateTime,
@CurrentYear_EndDate As DateTime,
@PreviousYear_StartDate As DateTime,
@PreviousYear_EndDate As DateTime,
@TodaysDate As DateTime,
@CurrentYear As Int

set @CurrentYear = year(getdate())
set @CurrentYear_StartDate = convert(DateTime, '01/01/' + cast(@CurrentYear As varchar))
set @CurrentYear_EndDate = convert(DateTime, '12/31/' + cast(@CurrentYear As varchar))
set @PreviousYear_StartDate = DateAdd(year,-1, @CurrentYear_StartDate)
set @PreviousYear_EndDate = DateAdd(year,-1, @CurrentYear_EndDate)

Select ITEMNMBR, ITEMDESC, Sum(PreviousYear_Sales) As PreviousYear_Sales, Sum(CurrentYear_Sales) As CurrentYear_Sales,
Sum(CurrentYear_Sales) - Sum(PreviousYear_Sales) As Variance
From
(
Select ITEMNMBR, ITEMDESC, PreviousYear_Sales=0, Sum(XTNDPRCE) As CurrentYear_Sales
From sop30200 m
Inner Join sop30300 d on d.sopnumbe = m.sopnumbe and m.soptype=3
Where DocDate >= @CurrentYear_StartDate and DocDate <= @CurrentYear_EndDate and m.SOPType=3 and voidstts=0
Group By ITEMNMBR, ITEMDESC
UNION
Select ITEMNMBR, ITEMDESC, Sum(XTNDPRCE) As PreviousYear_Sales, CurrentYear_Sales=0
From sop30200 m
Inner Join sop30300 d on d.sopnumbe = m.sopnumbe and m.soptype=3
Where DocDate >= @PreviousYear_StartDate and DocDate <= @PreviousYear_EndDate and m.SOPType=3 and voidstts=0
Group By ITEMNMBR, ITEMDESC
) As Table_Union
Group By ITEMNMBR, ITEMDESC
Order by CurrentYear_Sales DESC