title: How to remove unique key on particular mysql table field
body: <p>I have assigned unique key in two field username and email. I have execute this query.</p>
  
  <pre><code>ALTER TABLE goipmonl_users DROP INDEX username;
  
  DROP INDEX username ON goipmonl_users
  </code></pre>
  
  <p>It's show an error. So how can I remove unique key from selected field.</p>
  
  <pre><code>#1091 - Can't DROP 'username'; check that column/key exists.
  </code></pre>
  
  <p>I have username, email columns in my table.</p>