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