title: Change unique key together in mysql
body: <p>I have in my MYSQL table a unique key and i want to add to it.</p>
  
  <pre><code>UNIQUE KEY `user_id` (`user_id`,`account_id`)
  </code></pre>
  
  <p>and i want to add another </p>
  
  <pre><code>UNIQUE KEY `user_id` (`user_id`,`account_id`,`pet_id`)
  </code></pre>