title: In mongodb, how to add field from one collection document to another collection document based on criteria
body: <p>I am having 2 collections -</p>
  <ol>
  <li>Collection name is <strong>content</strong></li>
  </ol>
  <p><a href="https://i.stack.imgur.com/8IVLc.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/8IVLc.png" alt="enter image description here" /></a></p>
  <ol start="2">
  <li>Collection name is <strong>surveys</strong></li>
  </ol>
  <p><a href="https://i.stack.imgur.com/dlJiF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dlJiF.png" alt="enter image description here" /></a></p>
  <p>I actually want to add the &quot;type&quot; information from the content collection to every content in every survey in the &quot;surveys&quot; collection.</p>
  <p>I know in SQL we have to join these 2 tables first on _id and content_id commun columns and then add type column to suryeys table but not sure how should i do it here. I want the type value from content collection to add in every content field inside surveys collection. Please help me.</p>