title: How to combine multiple mongoose query in to one
body: <pre><code>User.find().then(function (user) {
      console.log(user)
  })
  Category.find().then(function (category) {
      console.log(err);
  })
  Content.find().then(function (content) {
      console.log(content);
  })
  </code></pre>
  
  <p>how can I combine the query sentences into one and get all result? ps: I use mongoose to operation mongoDb.</p>