group by子句 - Hibernate

14.11. group by子句 - Hibernate reference 3.2.0 ga 正式版中文参考手册

14.11. group by子句

一个返回汇集值(aggregate values)的查询能够按照一个返回的类或组件（components)中的任何属性（property）进行分组：

select cat.color, sum(cat.weight), count(cat) 
from Cat cat
group by cat.color

select foo.id, avg(name), max(name) 
from Foo foo join foo.names name
group by foo.id

having子句在这里也容许使用.

select cat.color, sum(cat.weight), count(cat) 
from Cat cat
group by cat.color 
having cat.color in (eg.Color.TABBY, eg.Color.BLACK)

若是底层的数据库支持的话(例如不能在MySQL中使用)，SQL的通常函数与汇集函数也能够出现 在having与order by 子句中。

select cat
from Cat cat
    join cat.kittens kitten
group by cat.id, cat.name, cat.other, cat.properties
having avg(kitten.weight) > 100
order by count(kitten) asc, sum(kitten.weight) desc

注意group by子句与 order by子句中都不能包含算术表达式（arithmetic expressions）. 也要注意Hibernate目前不会扩展group的实体,所以你不能写group by cat,除非cat的全部属性都不是汇集的(non-aggregated)。你必须明确的列出全部的非汇集属性。

http://doc.javanb.com/hibernate-reference-3-2-0-zh/ch14s11.html

 

Hibernate一个group by的例子

getHibernateTemplate().find("select df.cdwsjStatisticData.cdwsjWebsiteGroupCommunity.district.name from CdwsjStatisticDataField df where df.cdwsjStatisticTemplateField.tfieldid=? group by df.cdwsjStatisticData.cdwsjWebsiteGroupCommunity.district.name",templateFieldid);
若要加having语句的话应该是对df.cdwsjStatisticData.cdwsjWebsiteGroupCommunity.district.name的限制
where语句要加在group by的前面

http://zhangzuoyi.javaeye.com/blog/202458