title: Joining DynamoDB tables with AppSync
body: <p>I have 2 types:</p>
  
  <pre><code>type Location {
      id: ID!
      room: Int
      title: String
  }
  
  type Populate {
      id: ID!
      locationID: ID!
      location: Location
  }
  </code></pre>
  
  <p>I need to populate the <code>location</code> field when I call the GraphQL api. Locations are stored in DynamoDB. I know that a resolver is necessary but I haven't been a exactly how to write it. Thanks for the help!</p>