title: BigQuery - joining on a repeated field
body: <p>I'm trying to run a join on a repeated field.</p>
  
  <p>Originally I get an error:</p>
  
  <pre><code>Cannot join on repeated field payload.pages.action
  </code></pre>
  
  <p>I fix this by running flatten on the relevant table (this is only an example query - it will give empty result if it would successfully run):</p>
  
  <pre><code>SELECT 
    t1.repository.forks
  FROM publicdata:samples.github_nested t1
  left join each flatten(publicdata:samples.github_nested,payload.pages) t2 
  on t2.payload.pages.action=t1.repository.url
  </code></pre>
  
  <p>I get a different error:</p>
  
  <pre><code>Table wildcard function 'FLATTEN' can only appear in FROM clauses
  </code></pre>
  
  <p>This used to work in the past. Is there some syntax change?</p>