code: public Set<String> getInvokedTables() throws ParseException {
  
  	// Read all SQL statements from input
  	ZStatement st;
  	Set<String> tables = new HashSet<String>();
  
  	while ((st = parser.readStatement()) != null) {
  	    this.sql = st.toString();
  	    if (st instanceof ZQuery) { // An SQL query: query the DB
  		getInvokedTables((ZQuery) st, tables);
  	    }
  	    break;
  	}
  	return tables;
      }
docs: return all invoked tables by a sql statement
  
  @return invoked tables in a ArrayList
  @throws ParseException