hibernate的查询语法

DOM:Document Object Model
document.getElementById("id");
document.getElementByName("name");
document.getElementByTagName("tagName");

var tag=document.createElement("tagName");
appendChild();
removeChild();
parentNode
childNodes

one-to-many

T_Question

T_Choice
question_id

T_Image
question_id
choice_id

t_question_image  
question_id
image_id

用户，角色
t_user
t_role
用户角色表
t_user_role
user_id        primary key
role_id        primary key

多对多关系

一定要有一边需要配置inverse

如果两个对象都没有保存，有两种方式进行保存
1、cascade="save-update"
2、save 两次

一对一关系
eg. 用户  用户详情

Hibernate的查询分几种
HQL,QBC(QBE),SQL

HQL查询
HQL是基于面向对象的，里面没有表，也没有列，有类和属性
直接以from开头，表示全部选择
从Hibernate3.1可以执行修改和删除

from Emp

eg1.  带?参数查询
Session session = HibernateSessionFactory.getSession();
String hql="from Emp e where e.ename like ?";
Query query=session.createQuery(hql);
query.setString(0, "%"+"a"+"%");
List list=query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();

eg.2 带：命名参数
Session session = HibernateSessionFactory.getSession();   
String hql="from Emp e where e.ename like :name";
Query query=session.createQuery(hql);
query.setString("name", "%a%");
List list=query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();

eg3.in查询
Session session = HibernateSessionFactory.getSession();
String hql="from Emp e where e.empno in (:list)";
Query query=session.createQuery(hql);
query.setParameterList("list", new Long[]{1L,3L,5L});
List list=query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();

eg4.连接查询
Session session = HibernateSessionFactory.getSession();
String hql = "from Emp e where e.dept.dname like ?";
Query query = session.createQuery(hql);
query.setString(0, "%RE%");
List list = query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();

eg5. 笛卡尔积
Session session = HibernateSessionFactory.getSession();
String hql = "select e from Emp e,Dept";
Query query = session.createQuery(hql);
List list = query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();

eg6. 带条件
Session session = HibernateSessionFactory.getSession();
String hql = "select e from Emp e,Dept d where e.dept=d";
Query query = session.createQuery(hql);
List list = query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();

eg7. select 多个对象，会形成 List里面放Object数组，数组里面放对象
Session session = HibernateSessionFactory.getSession();
String hql = "select e,d from Emp e,Dept d where e.dept=d";
Query query = session.createQuery(hql);
List list = query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();

eg8. select 一列，就会形成这一列类型的集合，不会生成Object数组
Session session = HibernateSessionFactory.getSession();
String hql = "select e.empno from Emp e,Dept d where e.dept=d";
Query query = session.createQuery(hql);
List list = query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();

eg9. select多个值，会形成Object[]
Session session = HibernateSessionFactory.getSession();
String hql = "select e.empno,e.ename from Emp e,Dept d where e.dept=d";
Query query = session.createQuery(hql);
List list = query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();

eg10.查询生成List里面放HashMap,key由as后面的字符串决定
Session session = HibernateSessionFactory.getSession();
String hql = "select new map(e.empno as id,e.ename as name) from Emp e";
Query query = session.createQuery(hql);
List list = query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();

eg11.迫切左连接查询
Session session = HibernateSessionFactory.getSession();
String hql = "from Emp e left join fetch e.dept";
Query query = session.createQuery(hql);
List list = query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();

eg12.分页查询
Session session = HibernateSessionFactory.getSession();
String hql = "from Emp ";
Query query = session.createQuery(hql);
query.setFirstResult(10);//从第几条开始,初始是0  (page-1)*pageSize;
query.setMaxResults(5);//取几条
List list = query.list();
System.out.println(list.size());
HibernateSessionFactory.closeSession();