Question

I’m building an application for a University assignment, I’m using Visual Basic 2010 and Micrsoft Access for the database.

I have a form where customers can order products each product will have a set price, for example product1 is £1, however some customers will get products for cheaper so I have a table ‘special prices’ the special price table will contain rows including the ‘customerid’ ‘productid’ and the ‘specialprice’.

I need to know how to display the price, if a customer chooses product1 I need my application to first check if they have a special price and if not just display the normal price,

Thanks,

Jack.

Answer 1

If Customer does not have a special price, it is null

SELECT p.Price, c.CustomerID, sp.SpecialPrice, IFNULL(sp.SpecialPrice, p.Price) As UsedPrice
FROM Product p
LEFT JOIN SpecialPrice sp ON p.ProductID = sp.ProductID
AND sp.CustomerID = 123

My answer is based on SQL Server I hope you can translate it to MSAccess. The main point is Join the Product table to special price table where current customer. If special price is available use it, otherwise use price in Product

OR in code

if(row["SpecialPrice"] != null) // if(row["SpecialPrice"] != DBNull.Value) --- instead
  price = row["SpecialPrice"];
else
  price = row["Price"];