title: Azure Cosmos DB - Update existing documents with an additional field
body: <p>Existing Cosmos DB documents need to be altered/updated with a new property &amp; also existing documents of other collections need to be updated with the same new property along with its value.</p>
  <p>Is there any recommended way or tool available to update existing documents on Cosmos DB, or is writing the custom c# application/PowerShell script using Cosmos DB SDK is the only option?</p>
  <p>Example:</p>
  <p>Existing <code>user</code> document</p>
  <pre class="lang-json prettyprint-override"><code>{
     id:user1@mail.com,
     name: &quot;abc&quot;,
     country: &quot;xyz&quot;
  }  
  </code></pre>
  <p>Updated <code>user</code> document</p>
  <pre class="lang-json prettyprint-override"><code>{
     id:user1@mail.com,
     name: &quot;abc&quot;,
     country: &quot;xyz&quot;,
     guid:&quot;4334fdfsfewr&quot;  //new field
  } 
  </code></pre>
  <p>Existing <code>order</code> document of the <code>user</code></p>
  <pre class="lang-json prettyprint-override"><code>{
     id:user1@mail.com,
     user: &quot;user1@mail.com&quot;,
     date: &quot;09/28/2020&quot;,
     amt: &quot;$45&quot;
  }  
  </code></pre>
  <p>Updated <code>order</code> document of the <code>user</code></p>
  <pre class="lang-json prettyprint-override"><code>{
     id:user1@mail.com,
     user: &quot;user1@mail.com&quot;,
     userid: &quot;4334fdfsfewr&quot;,  // new field but with same value as in user model
     date: &quot;09/28/2020&quot;,
     amt: &quot;$45&quot;
  }  
  </code></pre>