title: Is it necessary to rebuild index after changing column default value?
body: <p>Is is necessary to drop and re-create an index involving a particular column when that column is altered so that the default value is changed? My column looks like <code>SubNum varchar(8) NOT NULL DEFAULT ''</code> and I want to change it to <code>SubNum varchar(8) NOT NULL</code>. My related indexes looks like:</p>
  <pre><code>KEY `Docs1` (`First`,`SubNum`,`DocNum`),
  KEY `Docs2` (`SubNum`,`DocNum`),
  </code></pre>
  <p>I'm using MySQL version 5.5.49 and the table is <code>MyIsam</code>.</p>