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();