Hi,
Try this query
SELECT T0.ItemCode,
Max(T0.ItemName) 'Item Description',
Max(T3.[ItmsGrpNam]) 'Item Group',
Max(T6.[FirmName]) AS [Brand],
Max(IsNull(T0.OnHand,0)) 'In Stock',
SUM(IsNull(T1.Quantity,0)) 'Quantity',
Sum(IsNull(T1.LineTotal,0)) 'Sales Amt',
SUM(IsNull(T1.GrssProfit,0)) 'Gross Profit',
Case WHEN Sum(Isnull(T1.LineTotal,0)) = 0 THEN 0 ELSE
SUM(IsNUll(T1.GrssProfit,0))/Sum(Isnull(T1.LineTotal,0)) * 100 END 'Gross Profit %'
FROM OITM T0
LEFT JOIN INV1 T1 ON T1.ItemCode=T0.ItemCode
LEFT JOIN OINV T2 ON T2.DocEntry=T1.DocEntry
INNER JOIN OITB T3 ON T0.ItmsGrpCod = T3.ItmsGrpCod
LEFT JOIN OMRC T6 ON T0.FirmCode = T6.FirmCode
WHERE T6.[FirmName]=[%0] AND T2.DocDate Between [%1] and [%2]
GROUP BY T0.ItemCode