title: Bigquery union two arrays of different struct
body: <p>I have two tables</p>
  
  <p><code>v1
  ARRAY&lt;STRUCT&lt;a int64&gt;&gt;</code></p>
  
  <p>and</p>
  
  <p><code>v2
  ARRAY&lt;STRUCT&lt;a int64, b int64&gt;&gt;</code></p>
  
  <p>I want to write query which unions both tables using <code>union all</code> and for <code>v1</code> rows put nulls in place of <code>b</code> field. Any help is appreciated :)</p>
  
  <p>I'm using standard SQL.</p>