计算每个产品（Inkcode）库存

Question

我有2个表Tblinkreceiving和Tblinkdelivery。我想显示每个墨水代码的库存余额。我尝试了下面的sql连接查询但是当我在手动计算中交叉检查时，许多墨水码的计算是错误的。哪里出错了？

select r.inkcode, SUM(r.quantity) Stock-In, SUM(d.quantity) Stock-out, (SUM(r.quantity) - SUM(d.quantity)) Stock-Balance from Tblinkreceiving r,Tblinkdelivery d where r.inkcode=d.inkcode
group by r.inkcode;

Answer 1

WITH    i AS
        (
        SELECT  inkcode, SUM(quantity) AS qin
        FROM    tblInkReceiving
        GROUP BY
                inkcode
        ),
        o AS
        (
        SELECT  inkcode, SUM(quantity) AS qout
        FROM    tblInkDelivery
        GROUP BY
                inkcode
        )
SELECT  COALESCE(i.inkcode, o.inkcode) AS inkcode,
        COALESCE(qin, 0) AS stock_in,
        COALESCE(qout, 0) AS stock_out,
        COALESCE(qin, 0) - COALESCE(qout, 0) AS stock_balance
FROM    i
FULL JOIN
        o
ON      o.inkcode = i.inkcode

Answer 2

您已使用内部联接（隐式）来组合接收和传递。这意味着任何已收到但未送达的墨水代码都将从您的结果中排除。

如果您可以假设对于任何墨水交付必须有墨水收据（基于您无法提供您尚未收到的东西的前提），那么您可以在tblInkReceiving上使用内部联接，如下所示：

SELECT r.inkcode, 
    SUM(r.quantity) AS Stock-In, 
    ISNULL(SUM(d.quantity), 0) AS Stock-out,
    SUM(r.quantity) - ISNULL(SUM(d.quantity), 0) AS Stock-Balance 
FROM Tblinkreceiving r LEFT JOIN Tblinkdelivery d ON r.inkcode = d.inkcode
GROUP BY r.inkcode

左连接将返回左侧（r）的所有记录，包括右侧的匹配记录（d）。如果d没有匹配记录（即该墨水代码没有墨水交付），那么这些行的值将为空。

如果您不能假设墨水只能在收到墨水后才能送出，那么您还需要链接到墨水表（即墨水代码为主键的表格），或者联合全部接收和交付表中的墨水代码，并链接到：

;WITH cte AS (SELECT inkcode FROM Tblinkreceiving 
    UNION 
    SELECT inkcode FROM Tblinkdelivery)
SELECT cte.inkcode, 
    SUM(r.quantity) AS Stock-In, 
    ISNULL(SUM(d.quantity), 0) AS Stock-out,
    SUM(r.quantity) - ISNULL(SUM(d.quantity), 0) AS Stock-Balance 
FROM cte LEFT JOIN Tblinkreceiving r ON cte.ink_code = r.ink_code
    LEFT JOIN Tblinkdelivery d ON cte.inkcode = d.inkcode
GROUP BY cte.inkcode