Hibernate查询语言HQL连接查询实例。
hql连接查询：
* 内连
* 外连接（左连接/右连接）
例子代码如下：
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/** * 连接查询 */ public class JoinQueryTest extends TestCase { public void testQuery1() { Session session = null; try { session = HibernateUtils.getSession(); session.beginTransaction(); //List students = session.createQuery(“select c.name, s.name from Student s join s.classes c”).list(); List students = session.createQuery (“select c.name, s.name from Student s inner join s.classes c”) .list(); for (Iterator iter=students.iterator(); iter.hasNext();) { Object[] obj = (Object[])iter.next(); System.out.println(obj[0] + ”,” + obj[1]); } session.getTransaction().commit(); }catch(Exception e) { e.printStackTrace(); session.getTransaction().rollback(); }finally { HibernateUtils.closeSession(session); } } public void testQuery2() { Session session = null; try { session = HibernateUtils.getSession(); session.beginTransaction();
List students = session.createQuery (“select c.name, s.name from Classes c left join c.students s”).list(); for (Iterator iter=students.iterator(); iter.hasNext();) { Object[] obj = (Object[])iter.next(); System.out.println(obj[0] + ”,” + obj[1]); } session.getTransaction().commit(); }catch(Exception e) { e.printStackTrace(); session.getTransaction().rollback(); }finally { HibernateUtils.closeSession(session); } } public void testQuery3() { Session session = null; try { session = HibernateUtils.getSession(); session.beginTransaction(); List students = session.createQuery (“select c.name, s.name from Classes c right join c.students s”).list(); for (Iterator iter=students.iterator(); iter.hasNext();) { Object[] obj = (Object[])iter.next(); System.out.println(obj[0] + ”,” + obj[1]); } session.getTransaction().commit(); }catch(Exception e) { e.printStackTrace(); session.getTransaction().rollback(); }finally { HibernateUtils.closeSession(session); } } } |