title: Any CONCAT() variation that tolerates NULL values?
body: <p>CONCAT() returns NULL when any value is NULL. I have to use IFNULL() to
  wrap all fields passed to CONCAT(). Is there a CONCAT() variation that just
  ignores NULL?</p>
  
  <p>For example:</p>
  
  <pre><code>#standardSQL
  WITH data AS (
    SELECT 'a' a, 'b' b, CAST(null AS STRING) nu
  )
  
  SELECT CONCAT(a, b, nu) concatenated, ARRAY_TO_STRING([a,b,nu], ',') w_array_to_string
  FROM `data`
  
  ---&gt;
  null
  </code></pre>