title: how to update whole database without losing data
body: <p>I am using mysql database for my site.
  I have create one site using codeigniter php framework and mysql.</p>
  
  <p>Now after few months I have updated that site and also the database.
  I have added some new columns to my database table not deleted or alert any previous one.</p>
  
  <p>Now I want to update my site but don't want to lose data that I already have right now.</p>
  
  <p>Is there anyway I can update database without losing the data present in it.</p>