Thanks for your help, Paul
We have Credit Notes not related to Invoices, so i had to use DocDate, CardNum, ItemCode as key
The Final query i got is:
SELECT DocDate, CardCode, CardName, ItemCode, Dscription, SUM(Quantity) AS Quantity, U_KGSXPZA, Quantity * U_KGSXPZA AS Expr1
FROM (SELECT T0.DocDate, T0.CardCode, T0.CardName, T1.ItemCode, T1.Dscription, T1.Quantity, T2.U_KGSXPZA
FROM dbo.OINV AS T0 INNER JOIN
dbo.INV1 AS T1 ON T1.DocEntry = T0.DocEntry INNER JOIN
dbo.OITM AS T2 ON T1.ItemCode = T2.ItemCode
WHERE (T0.DocType = 'I')
UNION ALL
SELECT T0.DocDate, T0.CardCode, T0.CardName, T1.ItemCode, T1.Dscription, - T1.Quantity AS 'Quantity', T2.U_KGSXPZA
FROM dbo.ORIN AS T0 INNER JOIN
dbo.RIN1 AS T1 ON T1.DocEntry = T0.DocEntry INNER JOIN
dbo.OITM AS T2 ON T1.ItemCode = T2.ItemCode
WHERE (T0.DocType = 'I')) AS S
GROUP BY DocDate, CardCode, CardName, Dscription, ItemCode, U_KGSXPZA, Quantity * U_KGSXPZA
ORDER BY 'Quantity' DESC
Regards!!
