title: What are the possible values of the Hibernate hbm2ddl.auto configuration and what do they do
body: <p>I really want to know more about the update, export and the values that could be given to <code>hibernate.hbm2ddl.auto</code><br>
  I need to know when to use the update and when not? And what is the alternative?</p>
  
  <p>These are changes that could happen over DB:</p>
  
  <ul>
  <li>new tables</li>
  <li>new columns in old tables</li>
  <li>columns deleted</li>
  <li>data type of a column changed</li>
  <li>a type of a column changed its attributes</li>
  <li>tables dropped</li>
  <li>values of a column changed </li>
  </ul>
  
  <p>In each case what is the best solution?</p>