title: Application Insights Analytics doing sub selects
body: <p>I am using this reference <a href="https://docs.microsoft.com/en-us/azure/application-insights/app-insights-analytics-reference" rel="nofollow noreferrer">documentation</a> for Application Insights.</p>
  
  <p>How can I do a sub-select using the output of a different query?</p>
  
  <pre><code>//Query 1
  Events 
  | where  Timestamp &gt;= ago(30min) and Data contains('SomeString')
  | project TraceToken
  
  //I would like to use the first query's output in the subselect here.
  Events 
  | where TraceToken in ({I would like to use the First query's output here.})
  </code></pre>
  
  <p>Is a join better in this scenario. Which would have better performance.</p>