Union de dos consultas o restar dos tablas

[Libras]

puedes hacerlo con 2 subquerys:

Código SQL:

SELECT * FROM(
SELECT V.ItemCode AS CODIGO_ITEM, V.Dscription, SUM(V.Quantity)AS TOTAL_VENDIDOS, S.whsname AS BODEGA,W.OnHand AS EN_STOCK
FROM INV1 V 
INNER JOIN OITW W ON V.ItemCode=W.ItemCode 
INNER JOIN OITM M ON V.ItemCode=M.ItemCode 
INNER JOIN OITB B ON M.ItmsGrpCod=B.ItmsGrpCod 
INNER JOIN OWHS S ON W.WhsCode=S.WhsCode
WHERE V.DocDate BETWEEN '20130101' AND '20140430' AND W.WhsCode = 02
GROUP BY V.ItemCode, S.whsname, W.OnHand, V.Dscription
) AS t1 LEFT JOIN
 
(SELECT DISTINCT ItemCode, SUM(Quantity) AS CANTIDAD_DEVUELTA, WhsCode AS bodega
FROM RIN1
WHERE DocDate BETWEEN '20130101' AND '20140430' AND WhsCode=02
GROUP BY ItemCode, WhsCode) AS t2 ON (t1.codigo=t2.itemcode)
 

con eso obtendrias los datos que necesitas restar ahora te corresponde a ti terminar el query :)