title: How to set precision and scale in ALTER TABLE
body: <p>I have working code with PostgreSQL 9.3:</p>
  
  <pre><code>ALTER TABLE meter_data ALTER COLUMN w3pht TYPE float USING (w3pht::float);
  </code></pre>
  
  <p>but don't know how to set <strong>precision</strong> and <strong>scale</strong>.</p>