Hibernate在PostgreSQL上执行sum函数导致数据失真的问题

     有一段通过Hibernate从PostgreSQL上进行sum统计的简单代码,但统计结果却导致数据失真,不知原因何在,求指教!

     Java代码片段如下:

public List<Object> getSalesRanking( ) throws Exception{
    StringBuilder sbHql = new StringBuilder();
    sbHql.append("select dl.dishId, dl.dishName, sum(dl.counts) as t, sum(dl.price) as s from R311dishList dl ")
         .append(" where dl.dishName='松仁玉米'")
        .append(" group by dl.dishId, dl.dishName");
    String hql = sbHql.toString();

    SQLQuery query = sf.getCurrentSession().createSQLQuery(hql);        
    query.addScalar("dishId", StandardBasicTypes.STRING);
    query.addScalar("dishName", StandardBasicTypes.STRING);
    query.addScalar("t", StandardBasicTypes.DOUBLE);
    query.addScalar("s", StandardBasicTypes.DOUBLE);
        
    List<Object> list = new ArrayList<Object>();
    ScrollableResults rs = query.scroll();        
    while(rs.next()){
        try{
            Object[] obj = new Object[4];
            obj[0] = rs.getString(0);
            obj[1] = rs.getString(1);
            obj[2] = rs.getDouble(2);
            obj[3] = rs.getDouble(3);

            list.add(obj);
        }
        catch(Exception ex){
            String err = ex.toString();
            throw ex;
        }
    }
    return list;
}

 

   对应的数据库表R311DishList中相关数据如下:

 image

 

     请注意,要统计的counts字段的数据分别是2.4/2.3/2.6,counts字段是double类型的,按道理sum(counts)后的结果应该是7.3,且通过SQL直接在数据库上执行的结果也确实是7.3,如下图:

   image

     可是,通过代码执行得到的结果却是7.299999999999999:

   image

 

    修改数据库中三条记录的counts值为其他值均正常,且偶尔调整三条记录的顺序后也能正常显示。不知何故??

posted on 2013-07-18 13:45  野文  阅读(2095)  评论(2编辑  收藏  举报