Hibernate HQL查询必知

Sql代码

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

//HQL-AssociationsString 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();

 

Sql代码

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

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

 

Sql代码

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

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

 

Sql代码

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

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

 

Sql代码

1. //HQL-Named Parameters   
2. String hql = "from Product where price > :price";   
3. Query query = session.createQuery(hql);   
4. query.setDouble("price",2.0);   
5. List results = query.list();   
6. String hql = "from Product as product where product.supplier=:supplier";   
7. Query query = session.createQuery(hql);   
8. query.setEntity("supplier",supplier);   
9. List results = query.list();  

//HQL-Named ParametersString 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();

 

Sql代码

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

//HQL-UpdateString 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();

 

Sql代码

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

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

 

Sql代码

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

//HQL-MapString 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】

Sql代码

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

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:

Sql代码

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

select cust.name.firstName from Customer as custselect 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:

Sql代码

1. select mother, offspr, mate.name  
2. from DomesticCat as mother   
3.     inner join mother.mate as mate   
4.     left join mother.kittens as offspr  

select mother, offspr, mate.namefrom 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:

Sql代码

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

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):

Sql代码

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

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:

Sql代码

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

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

 

这种做法在与子句select new map一起使用时最有用:

Sql代码

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