"In stock" problem

[LesleyParker]

I have this problem when creating a database :
I want to make a database that simulates a real life shop.
I have 3 tables : "Products", "Customers" and "Purchases". In the Products table, I have a field called "In Stock" and it basically says how many of each product is in stock in the shop at the moment.
My question is : Is it possible to make it so that everytime a customer makes a purchase, the products "In Stock" number automatically decreased by however many he bought?
Thanks in advance. =]

 

[pbaldy]

Good discussion here to get you started:

http://allenbrowne.com/AppInventory.html

 

[LesleyParker]

Thanks a lot mate, I'll check it out.

 

[LesleyParker]

How do I apply the DSum() function to the table?

 

[ajetrumpet]

Good discussion here to get you started:

http://allenbrowne.com/AppInventory.html

It's more of a lecture than a discussion Paul.

How do I apply the DSum() function to the table?

Look it up in Help. You can find the syntax there, and probably a much shorter example to learn from.

There are many ways to use it. Your question is just too short to decipher if you need to use a recordset or a query, or something else perhaps...