Hibernate对多个表进行查询时，
查询结果是多个表的笛卡尔积，或者称为“交叉”连接。例如：
from Student, Book
from Student as stu, Book as boo
from Student stu, Book boo
注意：让查询中的Student和Book均是表student和book对应的类名，它的名字一定要和类的名字相同，包括字母的大小写。别名应该服从首字母小写的规则是一个好习惯，这和Java对局部变量的命名规范是一致的。
建议通过MyEclipse进行生成这样就不会出太多的错注意表名要与类名同名
下面列举一个完整的例子来说明Hibernate对多个表进行关联查询（其中粗体是我们要特别注意的地方，相应表tBookInfo和BookSelection的结构和其对应的hbm.xml、class文件就不一一列举了，有需要详细了解的朋友，请联系我）：
String sTest = "from tBookInfo book, BookSelection sel where book.id = sel.bookId";
Collection result = new ArrayList();
Transaction tx = null;
try ...{
Session session = HibernateUtil.currentSession();
tx = session.beginTransaction();
Query query = session.createQuery(sql);
result = query.list();
tx.commit();
} catch (Exception e) ...{
throw e;
} finally ...{
HibernateUtil.closeSession();
}
ArrayList sList = (ArrayList) result;
Iterator iterator1 = sList.iterator();
while (iterator1.hasNext()) ...{
Object[] o = (Object[]) iterator1.next();
tBookInfo bookInfo = (tBookInfo) o[0];
BookSelection bookSelect = (BookSelection) o[1];
System.out.println("BookInfo-Title: " + bookInfo.getTitle());
System.out.println("BookSelection-BookSelectionId: " + bookSelect.getId());
}
方法二
public List queryResoursOut() ...{
log.debug("queryResoursOut instance");
List list = new ArrayList();
ScrollableResults srs = null;
Session session = null;
try ...{
session = getSession();
srs = session.createQuery(
"select m.cname , t.cname , o.price , o.quantity "
+ "from ResourceModel m, ResourceType t, ResourceExist o"
+ " where m.id = o.modid and t.id = o.typeid and m.delflag =\'0\' and t.delflag = \'0\' order by o.typeid ").scroll();
// 将查询结果放入List保存
while (srs.next()) ...{
list.add(new ResourceOutTemp(srs.getString(0),
srs.getString(1), srs.getFloat(2), srs.getLong(3)));
}
} catch (HibernateException he) ...{
if (srs != null) ...{
try ...{
srs.close();
} catch (Exception e) ...{
;
}
}
} finally ...{
try ...{
session.close();
} catch (Exception e) ...{
;
}
}
return list;
}
ScrollableResults 是import org.hibernate.ScrollableResults;
提供的类，它可以为我们定制过虑输出列。