title: How to concatenate columns for one row without enumerating them?
body: <p>Given:</p>
  <pre><code>let table1 = datatable (col1:string, col2:string)
  [&quot;abc&quot;,&quot;def&quot;]
  ;
  let table2 = datatable (col3:string, col4:string)
  [&quot;ghi&quot;,&quot;jkl&quot;]
  
  </code></pre>
  <p>where <code>table1 | union table2</code> gives:</p>
  <pre><code>col1 col2 col3 col4
  abc  def
            ghi jkl
  </code></pre>
  <p>how to get this instead?</p>
  <pre><code>col1 col2 col3 col4
  abc  def  ghi jkl
  </code></pre>
  <p>Assume there might be many more columns, so any solution requiring enumerating all of them doesn't work.</p>
  <p>Related question:<br />
  <a href="https://stackoverflow.com/q/56802416/986533">Is there a way to combine data from two tables in Kusto?</a></p>