MS-Access：从 3 个表计算库存

Question

I was reading this post from StackOverFlow to adjust query to calculate stock from 3 tables. I have 3 tables tblItems , tblPurchase and tblSales . tblItems contains items information like below.

ItemCode    Description                 ItemClass   ItemCategory        ReorderLevel    Unit    Stop
IT000001    Tonner 226A                 Tonner      IT Accessories      10              Pc(s)   No
IT000002    Keyborad (A4Tech, Slim Key) Keyboard    IT Accessories      10              Pc(s)   No
IT000003    Mouse (Wireless)            Mouse       IT Accessories      10              Pc(s)   No
SI000001    A4 Size Paper               Paper       Office Stationary   10              Pc(s)   No
SI000002    Pen (Black)                 Pen         Office Stationary   10              Pc(s)   No
SI000003    Pen (Blue)                  Pen         Office Stationary   10              Pc(s)   No

Screenshots of my tables

tblItems:

tblPurchase:

tblSales:

And my expected result like below

In query result items details will come from tblItems . Sum purchase quantity per item and sum sales quantity per item then minus SalesQuantity from PurchaseQuantity to see stock.

Here is my query which gives me following warning.

SELECT DISTINCTROW tblItems.ItemCode, TblItems.Description, TblItems.ItemClass, TblItems.ItemCategory, TblPurchaseAgg.[pQuantity], TblSalesAggs.[sQuantity]
FROM (TblItems 

LEFT JOIN (SELECT TblItems.ItemCode AS ItemCode, Sum(TblPurchase.Quantity) AS pQuantity FROM TblItems LEFT JOIN TblPurchase ON TblItems.ItemCode = TblPurchase.ItemCode GROUP BY TblItems.ItemCode)  
AS TblPurchaseAgg ON TblItems.ItemCode = TblPurchaseAgg.ItemCode) 

LEFT JOIN 

(SELECT TblItems.ItemCode AS ItemCode, Sum(tblSales.Quantity) AS sQuantity FROM TblItems LEFT JOIN tblSales ON TblItems.ItemCode = tblSales.ItemCode GROUP BY TblItems.ItemCode)  AS TblSalesAggs ON TblItems.ItemCode = TblSalesAggs.ItemCode

GROUP BY TblItems.ItemCode, TblItems.Description, TblItems.ItemClass, TblItems.ItemCategory;

Seeking help to resolve the warning and get my expected output. Any help is greatly appreciated. Thanks in advance.

Answer 1

Could you pls use this -

SELECT 
tblItems.ItemCode, TblItems.Description, TblItems.ItemClass, TblItems.ItemCategory, TblPurchaseAgg.[pQuantity], TblSalesAggs.[sQuantity]
FROM TblItems 

LEFT JOIN (SELECT TblPurchase.ItemCode AS ItemCode, Sum(TblPurchase.Quantity) AS pQuantity FROM TblPurchase GROUP BY TblPurchase.ItemCode)  TblPurchaseAgg ON TblItems.ItemCode = TblPurchaseAgg.ItemCode
LEFT JOIN (SELECT tblSales.ItemCode AS ItemCode, Sum(tblSales.Quantity) AS sQuantity FROM tblSales GROUP BY tblSales.ItemCode) TblSalesAggs ON TblItems.ItemCode = TblSalesAggs.ItemCode

GROUP BY TblItems.ItemCode, TblItems.Description, TblItems.ItemClass, TblItems.ItemCategory;

Answer 2

You don't need the outer/first group. Since your item table will [probably] will never have duplicate items the records returned will always be unique.

the both left joins you are using is grouping by itemCode so they also will only return one record per item. so grouping overall is not required.

this could work for you:

    SELECT 
    tblItems.ItemCode, 
    TblItems.Description, 
    TblItems.ItemClass, 
    TblItems.ItemCategory, 
    TblPurchaseAgg.pQuantity, 
    TblSalesAggs.sQuantity,
    (TblPurchaseAgg.pQuantity - TblSalesAggs.sQuantity) as stock,
    TblItems.unit
FROM 
    (TblItems 
    LEFT JOIN 
        (
            SELECT 
                TblPurchase.ItemCode AS ItemCode, 
                Sum(TblPurchase.Quantity) AS pQuantity 
            FROM
                TblPurchase
            GROUP BY TblPurchase.ItemCode
        )  AS TblPurchaseAgg
    ON TblItems.ItemCode = TblPurchaseAgg.ItemCode) 
    LEFT JOIN 
    (
        SELECT 
            tblSales.ItemCode AS ItemCode, 
            Sum(tblSales.Quantity) AS sQuantity 
        FROM 
            tblSales
        GROUP BY tblSales.ItemCode
    )  AS TblSalesAggs 
    ON TblItems.ItemCode = TblSalesAggs.ItemCode