title: How to compute percentage in each group?
body: <p>I have a table called <code>events</code>, with 5000 entries.</p>
  
  <p>Each event has a <code>recorded_on</code> field that might be null or might not be.</p>
  
  <p>Each event also has an <code>artist</code> field, which is one of 10 distinct values.</p>
  
  <p>Is it within the abilities of SQL (SQLite specifically) to issue a single query that will return the names of artists and what percentage of their events have null as the value for <code>recorded_on</code>? As in</p>
  
  <pre><code>ARTIST | PERCENTAGE RECORDED
  ------------------------------
  Joe    | 49.2
  Sarah  | 17.8
  Mike   | 83.0
  </code></pre>