title: Standard SQL - Sum arrays in a column
body: <p>I have a question regarding BigQuery (using Standard SQL).</p>
  
  <p>Suppose I have the following data:</p>
  
  <pre><code>Id  Arrays
  1   [1, 4]
  2   [2]
  1   [3, 4, 6, 91]
  2   [0, 9, 1, 4, 0, 37]
  </code></pre>
  
  <p>I want to sum the arrays to the following output:</p>
  
  <pre><code>Id  Arrays
  1   [4, 8, 6, 91]
  2   [2, 9, 1, 4, 0, 37]
  </code></pre>
  
  <p>The number of elements in each array can vary. And the order of the summed result matters a lot.</p>
  
  <p>I considered user defined functions in Standard SQL, but failed.</p>
  
  <p>Can anyone tell me if this is possible to achieve by using standard SQL and if yes, how?</p>
  
  <p>It would be great if you can show me a sample code. Thanks in advance.</p>