c# – How can i add multiple date with same item having a primary key

Im trying to develop a windows forms application for medical shop

I have some tables like

  1. Users
  2. Dealers
  3. Item_master
  4. Stock_items

Now i have a date field in table [stock_items]

I have item_id as common field in tables [item_master] and [stock_items]…

And it is also a primary_key, foreign_key in [stock_items]

So now when i add new item to the stock it will get added over the already existing item into the stock..

For example if some item was already in record with quantity=3 and i add 10 more item to it, the total of the item will be 13

But the expiry date can be different for new coming items than existing item…

Please suggest me some solution.

Thank you.