Session session = HibernateUtil.getSession();
            con = session.connection();
            Statement st = null;
            String test =
                    "select  COUNT(table_name) from all_tables where table_name='AAA'";
            st = con.createStatement();
            ResultSet rt = st.executeQuery(test);
            rt.next();
            int exist = rt.getInt(1);
            System.out.println(exist);
            rt.close();
            if (exist > 0) {
                String drop = "drop table aaa";
//                st = con.createStatement();
                st.executeQuery(drop);
            }
            String sql = "create table aaa(NAME varchar(20) ,IDNO varchar(50) ,birthday varchar(50) , oldrate number, newrate number, re varchar(100))";
//            st = con.createStatement();
            st.executeQuery(sql);
            st.close();
            HibernateUtil.closeSession();上面我注释掉的代码st = con.createStatement();要不要写,有什么区别!