Hibernate 中聚合函数的使用

Hibernate 中聚合函数的使用

Criteria接口的Projections类主要用于帮助Criteria接口完成数据的分组查询和统计功能:

List cats = session.createCriteria(Cat. class )
               .setProjection(Projections.projectionList()
               .add(Projections.rowCount())
               .add(Projections.avg( " weight " ))
               .add(Projections.max( " weight " ))
               .add(Projections.min( " weight " ))
               .add(Projections.groupProperty( " color " ))
           ).addOrder(Order.asc( " color " )).list();

示例 代码相当于:

select  color, count ( * ), avg (weight), max (weight), min (weight), min (weight)  from  cat  group   by  color  order   by  color  asc ;