title: How to get a vlookup type experience from Power Query
body: <p>I have a table like this (with a dozen or so other columns I might add) which I'm bringing in from an external data source. What I need to be able to do is work out which IDs appear in the ParentID column, and have a column that basically says True or False in response to that question.</p>
  <p>So essentially in the example below - I'd want IDs 1,4 and 5 to have 'True' because those values appear in the ParentID column, and for the others to have False because they don't - So I don't want to exclude those rows or hide them, just mark them differently in my new column.</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID</th>
  <th>ParentID</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>1</td>
  <td>null</td>
  </tr>
  <tr>
  <td>2</td>
  <td>null</td>
  </tr>
  <tr>
  <td>3</td>
  <td>1</td>
  </tr>
  <tr>
  <td>4</td>
  <td>1</td>
  </tr>
  <tr>
  <td>5</td>
  <td>null</td>
  </tr>
  <tr>
  <td>6</td>
  <td>4</td>
  </tr>
  <tr>
  <td>7</td>
  <td>5</td>
  </tr>
  <tr>
  <td>8</td>
  <td>null</td>
  </tr>
  <tr>
  <td>9</td>
  <td>null</td>
  </tr>
  <tr>
  <td>10</td>
  <td>1</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>This is something that's really easy to do in Excel with a vlookup formula, and it might be easy to add a column in PowerQuery that can display this but I'm stumped, and don't know where to go with it. I've tried merging the table with itself but all that seems to achieve is identifying the rows that are true OR the rows that are false rather than indicating in a new column what the result is.</p>
  <p>There's got to be a way for this... hasn't there??</p>