title: Convert string to double (NOT decimal)
body: <p>I have a table of double precision values, and I need to insert new values calculated from strings with numeric meaning.</p>
  
  <p>MySQL doesn't seem to allow such conversion:</p>
  
  <pre><code>select cast('3.33' as double);
  </code></pre>
  
  <p>(error)</p>
  
  <pre><code>select cast('3.33' as decimal(3,2));
  </code></pre>
  
  <p>(works, but it's not what I need).</p>