title: Getting an error while updating a filed using another field in MongoDB 4.2
body: <p><strong>The Query Script</strong></p>
  <pre><code>db.getCollection('users').updateMany({'full_name':{$exists:false}},
      [
          {&quot;$set&quot;: {&quot;full_name&quot;: { &quot;$concat&quot;: [&quot;$name&quot;, &quot; &quot;] }}}
      ]         
  )
  </code></pre>
  <p><strong>Getting This Error</strong></p>
  <pre><code>Failed to execute script.
  
  Error: the update operation document must contain atomic operators 
  Details:
  DBCollection.prototype.updateMany@src/mongo/shell/crud_api.js:625:1
  @(shell):1:1
  </code></pre>