title: KQL: query all variables in dynamic column additional to existing columns
body: <p>I'm working with Microsoft azure Appinsights, and want to export Logs data to a CSV so I can analyze it with python. The problem is that there is one column named customDimensions, which is of dynamic type with a lot of important variables, which I want to have as separate columns. Furthermore, am I working with a lot of data, so I can't just hardcode the variables I want using 'extend', because every customDimensions value could consist of different variables.</p>
  
  <p>I found online that using bag_unpack comes near the solution I want:</p>
  
  <pre><code>union customEvents, pageViews
  | project customDimensions
  | evaluate bag_unpack(customDimensions)
  </code></pre>
  
  <p>However, this outputs only the new columns, not additional to the already existing columns. But when I don't use the 'project customDimensions' line, I get the following error: </p>
  
  <p><em>("evaluate bag_unpack(): the following error(s) occurred while evaluating the output schema: evaluate bag_unpack(): cannot add column named 'cloud_RoleName' as it already exists in expression source")</em></p>
  
  <p>The question is: How do I query to get all the variables in customDimensions as additional columns, instead of having it as a dictionary in the dataframe like this:</p>
  
  <p><a href="https://i.stack.imgur.com/K8fhX.png" rel="nofollow noreferrer">Dataframe with nested data instead of separate columns</a></p>
  
  <p><a href="https://i.stack.imgur.com/8P9od.png" rel="nofollow noreferrer">Want I want from the query</a></p>