title: onUpgrade() sqlite database in Android
body: <p>I created an Android application which, check at startup if there is a new version of application. If yes, the application download the new apk file and over-install new apk. 
  My application use the sqlite db. But this db, from one version to other can change.
  I think I have to use the method:</p>
  
  <pre><code> onUpgrade()
  </code></pre>
  
  <p>but I don't know exactly how to use it.</p>
  
  <p>When I start the application I use this code for crete database(if not exists):</p>
  
  <pre><code>DbHelper mDHelper = new DbHelper(context, DB_NAME, null, DB_VERSION)
  </code></pre>
  
  <p>What should I change if I want use <code>onUpgrade()</code> method?
  And when do I have to call it?</p>