HQL链接查询

和SQL查询一样，HQL也支持各种各样的连接查询，如内连接、外连接。我们知道在SQL中可通过join字句实现多表之间的连接查询。HQL同样提供了连接查询机制，还允许显示指定迫切内连接和迫切左外连接。HQL提供的连接方式如下表所示。

//迫切内连接查询    @Test    public void test1() {        Query query = session.createQuery("select distinct s from Pro s inner join fetch s.emps");        List<Pro> list = query.list();        for (Pro item : list                ) {            System.out.println(item.getProname());            for (Emp itme1 : item.getEmps()                    ) {                System.out.println(itme1.getEmpname());            }        }    }//左外链接    @Test    public void test2() {        Query query = session.createQuery("select distinct s from Pro s left outer join  s.emps");        List<Pro> list = query.list();        for (Pro item : list                ) {            System.out.println(item.getProname());            for (Emp itme1 : item.getEmps()                    ) {                System.out.println(itme1.getEmpname());            }        }    }//迫切左外链接    @Test    public void test3() {        Query query = session.createQuery("select distinct s from Pro s left outer join fetch s.emps");        List<Pro> list = query.list();        for (Pro item : list                ) {            System.out.println(item.getProname());            for (Emp itme1 : item.getEmps()                    ) {                System.out.println(itme1.getEmpname());            }        }    }//右链接    @Test    public void test4() {        Query query = session.createQuery("select distinct s from Pro s right  join s.emps");        List<Pro> list = query.list();        for (Pro item : list                ) {            System.out.println(item.getProname());            for (Emp itme1 : item.getEmps()                    ) {                System.out.println(itme1.getEmpname());            }        }    }