title: MongoDB join data inside an array of objects
body: <p>I have document like this in a collection called <strong>diagnoses</strong> :</p>
  
  <pre><code>   {
          "_id" : ObjectId("582d43d18ec3f432f3260682"),
          "patientid" : ObjectId("582aacff3894c3afd7ad4677"),
          "doctorid" : ObjectId("582a80c93894c3afd7ad4675"),
          "medicalcondition" : "high fever, cough, runny nose.",
          "diagnosis" : "Viral Flu",
          "addmissiondate" : "2016-01-12",
          "dischargedate" : "2016-01-16",
          "bhtno" : "125",
          "prescription" : [ 
              {
                  "drug" : ObjectId("58345e0e996d340bd8126149"),
                  "instructions" : "Take 2 daily, after meals."
              }, 
              {
                  "drug" : ObjectId("5836bc0b291918eb42966320"),
                  "instructions" : "Take 1 daily, after meals."
              }
          ]
      }
  </code></pre>
  
  <p>The <strong>drug</strong> id inside the prescription object array is from a separate collection called <strong>drugs</strong>, see sample document below :</p>
  
  <pre><code>{
      "_id" : ObjectId("58345e0e996d340bd8126149"),
      "genericname" : "Paracetamol Tab 500mg",
      "type" : "X",
      "isbrand" : false
  }
  </code></pre>
  
  <p>I am trying to create a mongodb query using the native node.js driver to get a result like this:</p>
  
  <pre><code>        {
                  "_id" : ObjectId("582d43d18ec3f432f3260682"),
                  "patientid" : ObjectId("582aacff3894c3afd7ad4677"),
                  "doctorid" : ObjectId("582a80c93894c3afd7ad4675"),
                  "medicalcondition" : "high fever, cough, runny nose.",
                  "diagnosis" : "Viral Flu",
                  "addmissiondate" : "2016-01-12",
                  "dischargedate" : "2016-01-16",
                  "bhtno" : "125",
                  "prescription" : [ 
                      {
                          "drug" : 
                          {
                            "_id" : ObjectId("58345e0e996d340bd8126149"),
                            "genericname" : "Paracetamol Tab 500mg",
                            "type" : "X",
                            "isbrand" : false
                          },
                          "instructions" : "Take 2 daily, after meals."
                      },
                      ...
                  ]
              }
  </code></pre>
  
  <p>Any advice on how to approach a similar result like this is much appreciated, thanks.</p>