title: e-commerce for subscriptions - application design dilemma
body: <p>I'm designing an application that offers subscribed members premium content.  Therefore the app includes e-commerce functionality so users can purchase subscriptions.  Below is a draft of the UML static diagram so far.<br>
  <img src="https://i.stack.imgur.com/mK7Gq.png" alt="enter image description here"></p>
  
  <p>While writing the DDL for the database table that will hold subscription information it seems like it should have foreign keys to both the Users table and the Payments table.  However, that seems to violate some basic database design concepts because it's possible to determine which payment originated from which user by going through the Orders table.  Is there a better way to design the classes than outlined in the diagram to eliminate redundancy?</p>