title: Presto SQL filter by data type in where clause
body: <p>I have a column, which should be VARCHAR; I need to cast these as doubles. Some values, however, are Booleans and trigger the error <code>Cannot cast false to DOUBLE</code>. How do I prevent this is the WHERE cause?</p>
  <p>What's the easiest way to accomplish the below in presto?</p>
  <pre class="lang-sql prettyprint-override"><code>...
  WHERE Type(col) != BOOL
  </code></pre>
  <p>Or</p>
  <pre class="lang-sql prettyprint-override"><code>...
  WHERE type(col) = VARCHAR 
  </code></pre>