title: How to do a simple join in GraphQL?
body: <p>I am very new in GraphQL and trying to do a simple join query. My sample tables look like below:</p>
  <pre><code>{
    phones: [
      {
        id: 1,
        brand: 'b1',
        model: 'Galaxy S9 Plus',
        price: 1000,
      },
      {
        id: 2,
        brand: 'b2',
        model: 'OnePlus 6',
        price: 900,
      },
    ],
    brands: [
      {
        id: 'b1',
        name: 'Samsung'
      },
      {
        id: 'b2',
        name: 'OnePlus'
      }
    ]
  }
  </code></pre>
  <p>I would like to have a query to return a <em>phone</em> object with its brand name in it instead of the brand code.</p>
  <p>E.g. If queried for the phone with <code>id = 2</code>, it should return:</p>
  <pre><code>{id: 2, brand: 'OnePlus', model: 'OnePlus 6', price: 900}
  </code></pre>