1.查询记录总数
错误:HQL:select count(1) from ....
正确:HQL:select count(*) from ....
2.Criteria的同一个条件不能复用,
例如
错误:
Criteria criteria = session.createCriteria(A.class); criteria.add(Restrictions.eq("field1","xx"); criteria.list(); criteria.add(Restrictions.eq("field1","yy");//出错 criteria.list();
正确:
Criteria criteria = session.createCriteria(A.class); criteria.add(Restrictions.eq("field1","xx"); criteria.list(); criteria=session.createCriteria(A.class); criteria.add(Restrictions.eq("field1","yy"); criteria.list();
3.criteria的rowcount返回的是Integer
错误:
Criteria criteria = XXDAO.getCriteria(XX.class); criteria.setProjection(Projections.rowCount()); int count = ((Long)procriteria.uniqueResult()).intValue();//错误
正确:
Criteria criteria = XXDAO.getCriteria(XX.class); criteria.setProjection(Projections.rowCount()); int count = ((Integer)procriteria.uniqueResult()).intValue();//正确
4.HQL对聚合函数count,sum返回的类型却是Long,这点要注意和3区分开。