在c＃Windowform中加入三个表减法

Question

我有三张桌子产品，购买和销售

Product
  Item_code    Item_Name
  1            Panadol
  2            Disprin
  3            Calpol
  4            Arinac

Purchase
  Item_code    Pur_Item_PackQuantity
      1             5
      1             4
      3             5
      4             6
 Sale
    Item_code   Item_Sale_Quantity
       1            5
       1            4
       3            5
       4            6

现在我想从Product表中获取所有Item_name，并从Sale and Purchase表中获取Sale.Item_Sale_Quantity + Purchase.Pur_Item_PackQuantity的总和，但我正在尝试给出以下查询产生错误

   string query = "SELECT Product.Item_Name,Product.Packing,Product.MRP,SUM(Purchase.Pur_Item_PackQuantity)-SUM(Sale.Item_Sale_Quantity)AS[Stock] FROM Purchase RIGHT JOIN Product ON Product.Item_Code = Purchase.Item_Code Group By Item_Name  ORDER BY Item_Name ";

        SqlConnection newcon = new SqlConnection("Data Source=.;Initial Catalog=mateenwin;User ID=sa;Password=123");
        SqlCommand newcommand = new SqlCommand(query, newcon);
        SqlDataAdapter dp = new SqlDataAdapter(newcommand);
        DataTable dttt = new DataTable();
        dp.Fill(dttt);
        dataGridView3.DataSource = dttt;

请帮我解决此问题

Answer 1

这是一个SQL查询修复。

select p.Item_Code, p.Item_Name, p.[Total],s.[Sold], p.Total - s.Sold as [Stock]
from (select pro.Item_Code, pro.Item_Name,sum(pur.Pur_Item_PackQuantity) as [Total] 
      from product pro left outer join purchase pur on pro.Item_code = pur.Item_Code
      group by pro.Item_Code,pro.Item_Name) as p
join (select pro.Item_Code ,sum(s.Item_Sale_Quantity) as [Sold] 
      from product pro left outer join sale s on pro.Item_Code = s.Item_Code
      group by pro.Item_Code) as s
on p.Item_Code = s.Item_Code
order by p.Item_Code asc

Answer 2

您需要将查询更改为：

string query = "
SELECT Product.Item_Name, Product.Packing,
 Product.MRP,SUM(Purchase.Pur_Item_PackQuantity)-SUM(Sale.Item_Sale_Quantity)
 AS [Stock] 
FROM Purchase RIGHT JOIN Product ON Product.Item_Code = Purchase.Item_Code
Group By Item_Name,Packing,MRP  
ORDER BY Item_Name 
";