eg.

String hql = "select dr.date,sum(dr.click_num) as cn from DailyRecord dr  ";

hql += " where 1=1 ";

hql += " and dr.date > :date ";

...

hql += " group by dr.date ";//(1)

hql += " order by dr.date desc ";

　　　Session session = getSessionFactory().openSession();

        List<Object> result = null;

        try {

            org.hibernate.Query query = session.createQuery(hql.toString());

            SqlUtil.setQueryParameter(query, paramMap);

            result = query.list();

        } finally {

            session.flush();

            session.close();

        }

此时，如果不加（1）处语句，进行查询，如果没有满足条件的记录，result不会为空，size = 1;但此时里面的Object每个域都会null

如果加了（1）处的分组语句，进行查询，如果没有满足条件的记录，result不会为空，但size = 0;