title: rake aborted! Mysql2::Error: Duplicate column name 'slug': ALTER TABLE `categories`
body: <p>Recently I implemented <code>friendly_id</code> on two models on my <strong>local</strong> rails application. I created two migrations <code>add_slug_to_categories</code> and <code>add_slug_to_services</code>. And did rest the steps and got <code>friendly_id</code> urls working. Then I pushed the same migrations changes to my production server. And then in production rails console I ran <code>Category.find_each(&amp;:save)</code> and <code>Service.find_each(&amp;:save)</code> and got it working on the production too. </p>
  
  <p>Then for some testing purpose on my local machine I took the <code>dump.sql</code> from the production and and dropped the existing db on my local by running <code>rake db:drop</code> and created by <code>rake db:create</code> and ran <code>rake db:migrate</code>. And then I pushed the <code>dump.sql</code> to the local db. Then when I ran <code>rails s</code> I got <code>migrations pending</code> error. So I went ahead and ran <code>rake db:migrate</code> again. Then I got </p>
  
  <pre><code>== 20170411073744 AddSlugToCategories: migrating ==============================
  -- add_column(:categories, :slug, :string)
  rake aborted!
  StandardError: An error has occurred, all later migrations canceled:
  
  Mysql2::Error: Duplicate column name 'slug': ALTER TABLE `categories` ADD `slug`  
  </code></pre>
  
  <p>I tried dropping the db and again creating many times. But I keep getting the same issue. Could somebody please tell how can I fix this?</p>