title: DISTINCT in ARRAY OF STRUCT in Bigquery
body: <p>I am looking for the way to make array of struct has unique value. Here the example table.</p>
  
  <p><a href="https://i.stack.imgur.com/rwq4m.png" rel="noreferrer"><img src="https://i.stack.imgur.com/rwq4m.png" alt="-------------------------------------"></a></p>
  
  <p>Into this
  <a href="https://i.stack.imgur.com/mbx7z.png" rel="noreferrer"><img src="https://i.stack.imgur.com/mbx7z.png" alt="enter image description here"></a></p>
  
  <p>I only found similar question <a href="https://stackoverflow.com/questions/53602131/array-agg-containing-distinct-structs">here</a>, but it I think it only caters 1 nested repeated column. But what if the tables contains 2 or more nested repeated columns? In this case, column <code>country</code>, and <code>product</code>.</p>