title: BigQuery - Possible to query for column datatype
body: <p>Is there a function that would allow us query the datatype of the column in BigQuery?</p>
  
  <p>I'd like to find something like this:</p>
  
  <pre class="lang-sql prettyprint-override"><code>WITH basket AS
      (SELECT "apple" AS fruit, 10 AS qty
      UNION ALL SELECT "pear" AS fruit, 7 AS qty
      UNION ALL SELECT "banana" AS fruit, 9 AS qty)
  
  -- !!this doesn't work!!:
  SELECT
      fruit,
      qty,
      DATA_TYPE(fruit) AS type1, 
      DATA_TYPE(qty) AS type2 
  FROM basket
  </code></pre>
  
  <p>in order to return something like this:</p>
  
  <pre><code>+--------+-----+--------+-------+
  | fruit  | qty | type1  | type2 |
  +--------+-----+--------+-------+
  | apple  |  10 | STRING | INT64 |
  | pear   |   7 | STRING | INT64 |
  | banana |   9 | STRING | INT64 |
  +--------+-----+--------+-------+
  </code></pre>
  
  <p>Of course, my <code>DATA_TYPE()</code> function doesn't exist and I couldn't find anything comparable in <a href="https://cloud.google.com/bigquery/docs/reference/standard-sql/functions-and-operators" rel="noreferrer">the docs</a></p>
  
  <p>Does this functionality exist somewhere that I am missing?</p>