group by子句 - Hibernate

14.11. group by子句 - Hibernate reference 3.2.0 ga 正式版中文參考手冊

14.11. group by子句

一個返回彙集值(aggregate values)的查詢能夠按照一個返回的類或組件（components)中的任何屬性（property）進行分組：

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子句在這裏也容許使用.

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)

若是底層的數據庫支持的話(例如不能在MySQL中使用)，SQL的通常函數與彙集函數也能夠出現 在having與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子句與 order by子句中都不能包含算術表達式（arithmetic expressions）. 也要注意Hibernate目前不會擴展group的實體,所以你不能寫group by cat,除非cat的全部屬性都不是彙集的(non-aggregated)。你必須明確的列出全部的非彙集屬性。

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

 

Hibernate一個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語句的話應該是對df.cdwsjStatisticData.cdwsjWebsiteGroupCommunity.district.name的限制
where語句要加在group by的前面

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