从购买和出售的产品中获取库存数量

Question

我一直致力于客户项目。我需要从已购买的产品数量和已售出的数量中获得库存。

这是我的SQL

SELECT DISTINCTROW tbl_itemmaster.product_code,tbl_itemmaster.unittype,tbl_itemmaster.color,SUM(tbl_purchasedetails.qty),SUM(tbl_saledetails.qty),(SUM(tbl_purchasedetails.qty)-SUM(tbl_saledetails.qty)) 
FROM (tbl_itemmaster LEFT JOIN tbl_saledetails ON tbl_itemmaster.[product_code] = tbl_saledetails.[product_code]) 
LEFT JOIN tbl_purchasedetails ON tbl_itemmaster.[product_code]=tbl_purchasedetails.[product_code] GROUP BY tbl_itemmaster.product_code,tbl_itemmaster.unittype,tbl_itemmaster.color

以下是sql的结果

-----------------------------------------------------------------
Product Code   Unit Type  Color     Purchase QTY  Sold QTY  Stock
-----------------------------------------------------------------
1001           KiloGram   Red       500           
500            Kilogram   White     1033          300       733
570            Kilogram   Black   
600            Kilogram   Pink   
9005           Kilogram   Magenta   800.5         
900            Kilogram   Green   
-----------------------------------------------------------------

产品代码 500 有三次购买条目，即500 + 400 + 133 = 1033购买数量
产品代码 500 只有一次销售条目，即100 = 100售出数量
产品代码 500 假设 933 库存数量
但为什么我卖出300的数量？
我的查询缺乏的地方？
请帮助!!!

Answer 1

您正在购买笛卡尔产品，因为产品有多次销售和购买。

解决方案是在加入之前进行聚合：

SELECT im.product_code, im.unittype, im.color,
       pd purchaseqty, sd.salesqty),
       (purchaseqty - salesqty)
FROM (tbl_itemmaster as im LEFT JOIN
      (SELECT product_code, SUM(qty) as salesqty
       FROM tbl_saledetails
       GROUP BY product_code
      ) as sd
      ON im.[product_code] = sd.[product_code]
     ) LEFT JOIN
     (SELECT product_code, SUM(qty) as purchaseqty
      FROM tbl_purchasedetails
      GROUP BY product_code
     ) as pd
     ON im.[product_code] = pd.[product_code];