title: Table not updating when chaging the service.xml and building the service in liferay
body: <p>I am developing the custom portlet for liferay.
  My problem is once I create service builder and build the service then in my database the table is created. I have some changes in my service.xml (some table column is added) but now when I build the service my database table is not updating the table column. It is as same as before.</p>
  
  <p>So can anyone guide me that why this happens? I am new to liferay and there is always some changes will occurs so I need to solve  this problem.</p>