按条件对象休眠分组

java sql hibernate hibernate-criteria

2022-09-01 01:45:09

我想使用休眠条件实现以下SQL查询：

SELECT column_name, aggregate_function(column_name)
FROM table_name
WHERE column_name <operator> value
GROUP BY column_name

我试图用休眠标准来实现这一点，但它没有成功。

任何人都可以给我一个例子，如何使用休眠标准做到这一点？谢谢！

答案 1

有关示例，请参阅此处。重点是使用投影类提供的、和相关的集合函数。groupProperty()

例如：

SELECT column_name, max(column_name) , min (column_name) , count(column_name)
FROM table_name
WHERE column_name > xxxxx
GROUP BY column_name

其等效标准对象为：

List result = session.createCriteria(SomeTable.class)       
                    .add(Restrictions.ge("someColumn", xxxxx))      
                    .setProjection(Projections.projectionList()
                            .add(Projections.groupProperty("someColumn"))
                            .add(Projections.max("someColumn"))
                            .add(Projections.min("someColumn"))
                            .add(Projections.count("someColumn"))           
                    ).list();

答案 2

分组通过在休眠中使用

这是生成的代码

public Map getStateCounts(final Collection ids) {
    HibernateSession hibernateSession = new HibernateSession();
    Session session = hibernateSession.getSession();
    Criteria criteria = session.createCriteria(DownloadRequestEntity.class)
            .add(Restrictions.in("id", ids));
    ProjectionList projectionList = Projections.projectionList();
    projectionList.add(Projections.groupProperty("state"));
    projectionList.add(Projections.rowCount());
    criteria.setProjection(projectionList);
    List results = criteria.list();
    Map stateMap = new HashMap();
    for (Object[] obj : results) {
        DownloadState downloadState = (DownloadState) obj[0];
        stateMap.put(downloadState.getDescription().toLowerCase() (Integer) obj[1]);
    }
    hibernateSession.closeSession();
    return stateMap;
}