SQL选择，求和和分组简单问题

问题描述

SELECT     Product.Name, SUM(Product.Quantity) AS Balance, SUM(Income.IncomeQuantity) AS income, SUM(ProductLog.Quantity) as sold
    FROM         Income INNER JOIN
                          Product ON Income.ProductID = Product.ID INNER JOIN
                          ProductLog ON Product.ID = ProductLog.ProductID GROUP BY Name

此查询无法正常工作.在产品表中，收入为三行，该查询仅返回两行，因为productLog表仅包含两个产品的数据.我如何选择productLog或收入是否不包含当前产品ID返回0

请参阅截图 http://imageshack.us/photo/my-images/12/capturezfs.png/ [ ^ ]

This query does not works correctly. In product table and income is three rows and this query returns only two because productLog table contains data only two products. how i can select if productLog or income does not contains current product id return 0

see screenshot http://imageshack.us/photo/my-images/12/capturezfs.png/[^]

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