假定Customer类和Order类之间为双向一对多关联关系.
Customer类包含的属性:
[java]
/**对象OID*/
private Long id;
/**Customer对象的姓名*/
private String name;
/**Customer对象的年龄*/
private int age;
/**与Customer对象的订单*/
private Set
hibernate映射文件:
[html]
Order类包含的属性:
[java]
/**对象OID*/
private Long id;
/**Order 对象的订单号*/
private String orderNumber;
/**Order 对象的订单价格*/
private double price;
/**与Order 对象关联的Customer对象*/
private Customer customer;
hibernate映射文件:
[html]
假设数据库中存在的数据为:
cusomters表
orders表:
以下为测试代码:
[java]
List result=session.createQuery("select c from Customer as c inner join c.orders where c.name like 'T%'")
.list();
Iterator it = result.iterator();
Customer customer=(Customer) it.next();
System.out.println(customer.getOrders().size());
Hibernate生成对应的SQL语句为:
[sql]
Hibernate:
select
customer0_.id as id4_,
customer0_.name as name4_,
customer0_.age as age4_
from
customers customer0_
inner join
orders orders1_
on customer0_.id=orders1_.customer_id
where
customer0_.name like 'T%'
Hibernate:
select
orders0_.customer_id as customer4_4_1_,//重复字段
orders0_.id as id1_,//重复字段
orders0_.id as id5_0_,
orders0_.orderNumber as orderNum2_5_0_,
orders0_.price as price5_0_,
orders0_.customer_id as customer4_5_0_
from
orders orders0_
where
orders0_.customer_id=
疑问:
上述sql语句中,注释重复字段与下面的字段重复了,为什么要重复检索orders的主键id和外键customer_id字段
另:
上述采用内链接方式检索,但其实做外连接,迫切做外连接,单表查询也会重复检索主键和外键字段