USE AdventureWorks;

DECLARE @CustID AS int;
SET @CustID = 3;

WITH YearlyCustOrdersCTE(OrderYear, TotalValue)
AS
(  SELECT YEAR(OrderDate), SUM(OrderQty*UnitPrice)
  FROM Sales.SalesOrderHeader AS H
    JOIN Sales.SalesOrderDetail AS D
      ON H.SalesOrderID = D.SalesOrderID
  WHERE CustomerID = @CustID
  GROUP BY YEAR(OrderDate)  )
SELECT Cur.*, Prev.TotalValue AS PrevTotalValue,
  (Cur.TotalValue/Prev.TotalValue - 1) * 100 AS Diff
FROM YearlyCustOrdersCTE AS Cur
  LEFT OUTER JOIN YearlyCustOrdersCTE AS Prev
    ON Cur.OrderYear = Prev.OrderYear + 1;