title: How to get the length of a repeated nested field in bigquery
body: <p>I have a table in bigquery where I have a repeated nested field called <code>author_names</code>. <a href="https://i.stack.imgur.com/2kJP2.png" rel="noreferrer"><img src="https://i.stack.imgur.com/2kJP2.png" alt="enter image description here"></a></p>
  
  <p>How can I get the length of the repeated nested field <code>author_names</code>? 
  e.g. for <code>article_id = 2049807276</code>, the length of the author names would be 2.</p>
  
  <p>I prefer the standard-sql syntax in bigquery.</p>