title: MySQL, IFNULL(), COALESCE() on String not replacing
body: <p>My statement should replace every <strong>empty</strong> <code>title_column</code> with <strong>'no name'</strong>, but it doesn't:</p>
  <pre class="lang-sql prettyprint-override"><code>SELECT COALESCE(main_table.title_column, 'no name') AS title
  FROM main_table;
  </code></pre>
  <p><code>IFNULL()</code> behaves the same way.</p>
  <p>What am I doing wrong ?</p>