title: How to do left join/look-up in mongoDB to return the count for the users id in each organization?
body: <p>I have 20 objects of organization and and 100+ users. I want to retrieve result for number of total employee each organization have ?</p>
  <p>I am trying aggregation look-up. But it's returning me empty array.</p>
  <pre><code>        let data = await organizationModel.aggregate([
              {
                  $lookup: {
                      from: &quot;employees&quot;,
                      localField: &quot;_id&quot;,
                      foreignField: &quot;organizationId&quot;,
                      as: &quot;output&quot;,
                  },
              },
          ]);
  
  </code></pre>
  <p>Organization Object :</p>
  <pre><code>{
  _id: ObjectId(213eawsdzamxxca23fccce1)
  orgName: alphaprintings
  orgPhone:4543 343 122
  orgLocation: Atlanta, USA
  orgEmail: contact@alphaprintings.com
  }
  </code></pre>
  <p>Employee Object :</p>
  <pre><code>{
  _id: ObjectId(431aacff90uhcce1)
  empName: Steven Decker
  empPhone:4543 343 122
  empLocation: Atlanta, USA
  empEmail: steven@alphaprintings.com,
  organizationId: 213eawsdzamxxca23fccce1
  }
  </code></pre>