title: How would I achieve this using Google App Engine Datastore?
body: <p>I am a beginner to Datastore and I am wondering how I should use it to achieve what I want to do.</p>
  
  <p>For example, my app needs to keep track of customers and all their purchases.</p>
  
  <p>Coming from relational database, I can achieve this by creating [Customers] and [Purchases] table.
  In Datastore, I can make [Customers] and [Purchases] kinds.</p>
  
  <p>Where I am struggling is the structure of the [Purchases] kind.</p>
  
  <p>If I make [Purchases] as the child of [Customers] kind, would there be one entity in [Customers] and one entity in [Purchases] that share the same key? Does this mean inside of this [Purchases] entity, I would have a property that just keeps increasing for each purchase they make?</p>
  
  <p>Or would I have one [Purchases] entity for each purchase they make and in each of these entities I would have a property that points to a entity in [Customers] kind?</p>
  
  <p>How does Datastore perform in these scenarios?</p>