Hibernate查询——（HQL）

//HQL-Associations
String hql = "select s.name, p.name, p.price from Product p inner join p.supplier as s";
Query query = session.createQuery(hql);
List results = query.list();

 

//HQL-Delete
String hql = "delete from Product where name = :name";
Query query = session.createQuery(hql);
query.setString("name","Product 1");
int rowCount = query.executeUpdate();

 

//HQL-Function
String hql = "select min(product.price), max(product.price) from Product product";
Query query = session.createQuery(hql);
List results = query.list();

 

//HQL-Fetch Associations HQL Inner Join
String hql = "from Supplier s inner join fetch s.products as p";
Query query = session.createQuery(hql);
List results = query.list();

 

//HQL-Named Parameters
String hql = "from Product where price > :price";
Query query = session.createQuery(hql);
query.setDouble("price",2.0);
List results = query.list();
String hql = "from Product as product where product.supplier=:supplier";
Query query = session.createQuery(hql);
query.setEntity("supplier",supplier);
List results = query.list();

 

//HQL-Update
String hql = "update Supplier set name = :newName where name = :name";
Query query = session.createQuery(hql);
query.setString("name","Supplier Name 1");
query.setString("newName","s1");
int rowCount = query.executeUpdate();

 

//HQL-where
String hql = "from Product where price > 2.0 and name like 'P%'";
Query query = session.createQuery(hql);
List results = query.list();

 

//HQL-Map
String hql = " select new map(usr.name as userName, usr.password as password) from User usr";
Query query = session.createQuery(hql);
List list = query.list();
Map goods =(Map)list.get(0);

【注】

String hql = " select new map(usr.name as userName, usr.password as password) 
 from com.jason.User usr";
String hql = " select new map(usr.name as userName, usr.password as password) 
 from com.jason.User usr";

由于from之前的空格，引起unexpected token: from

查询语句可以返回值为任何类型的属性或对象，包括返回类型为某种组件(Component)的属性:

select cust.name.firstName from Customer as cust
select cat.mate from Cat cat

 

查询语句可以返回多个对象和（或）属性，存放在 Object[]队列中:

select mother, offspr, mate.name
from DomesticCat as mother
    inner join mother.mate as mate
    left join mother.kittens as offspr

或存放在一个List对象中:

select new list(mother, offspr, mate.name)
from DomesticCat as mother
    inner join mother.mate as mate
    left outer join mother.kittens as offspr

 

也可能直接返回一个实际的类型安全的Java对象(假设类Family有一个合适的构造函数):

select new Family(mother, mate, offspr)
from DomesticCat as mother
    join mother.mate as mate
    left join mother.kittens as offspr

也可以使用关键字as给“被选择了的表达式”指派别名:

select max(bodyWeight) as max, min(bodyWeight) as min, count(*) as n
from Cat cat

 

这种做法在与子句select new map一起使用时最有用:

select new map( max(bodyWeight) as max, min(bodyWeight) as min, count(*) as n )
from Cat cat

 

原文出自于：http://www.blogjava.net/gm_jing/articles/66179.html