Sql表连接查询

Question

I have 3 tables in sql

1. ProductMaster with column ProductName
2. PurchaseData with column ProductName and Quantity
3. SaleData with column ProductName and Quantity

Please guide me to write query for table join to get the result as under

PRODUCT1   10    5     5
PRODUCT2   10    0     10
PRODUCT3   10    5     5

Answer 1

Try to start with something like this:

SELECT [ProductMaster].[ProductName]
    ,[PurchaseData].[Quantity]  AS [PurchasedQuantity]
    ,[SaleData].[Quantity]      AS [SoldQuantity]
    ,[PurchaseData].[Quantity] 
        - [SaleData].[Quantity] AS [ClosingStock]
  FROM [ProductMaster]
    LEFT OUTER JOIN [PurchaseData]
        ON [ProductMaster].[ProductName] = [PurchaseData].[ProductName]
    LEFT OUTER JOIN [SaleData]
        ON [ProductMaster].[ProductName] = [SaleData].[ProductName]

The idea is to have the master table and join the two dependent tables to the master with an INNER JOIN on the ProductName field.

Answer 2

You don't need anymore ProductMaster Table, because all information you need are in PURCHASEDATA and SALEDATA

SELECT P.[ProductName] as ProductName, P.PurchaseQty, S.SalteQTY, P.purchaseQTY-S.SalteQTY as ClosingQty

  FROM [PURCHASEDATA] P LEFT OUTER JOIN [SALEDATA] S ON P.ProductName=S.ProductName