hibernate 中的批量查询

最新推荐文章于 2020-02-21 09:39:37 发布

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最新推荐文章于 2020-02-21 09:39:37 发布

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分类专栏： java 文章标签： hibernate

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本文详细介绍了Hibernate中的批量查询方法，包括HQL查询的多表操作、条件、分页、排序和统计，Criteria查询的单表操作及原生SQL查询用于处理复杂业务。通过这些查询方式，开发者可以更高效地进行数据检索。

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四：批量查询

1、HQL查询(多表查询,但不复杂时使用)

面向对象的查询语言

基本查询

        String sql = "from Customer";
        Query query = session.createQuery(sql);
        List<Customer> list = query.list();
        //Object uniqueResult = query.uniqueResult();//获得单个的对象

条件查询(1)

        String sql="from Customer where cust_id = :cust_id"; //:cust_id为下边这是的那个cust_id
        Query query = session.createQuery(sql);
        query.setParameter("cust_id", 1l);
        Object uniqueResult2 = query1.uniqueResult();  //返回查询结果

条件查询(2)

    String hql="from Customer where cust_id=?";
    Query qr = session.createQuery(hql);
    qr.setParameter(0, 1l);
    Customer customer = (Customer) qr.uniqueResult();

分页查询

        String sql = "from Customer";
        Query query = session.createQuery(sql);
        query.setFirstResult(0);  //与limit里的？，？一样，从第几个开始  （索引从0开始计数）
        query.setMaxResults(2);   //显示几个
        List<Customer> list = query.list();

排序查询

    String hql="from Customer order by cust_id desc";
    Query qr = session.createQuery(hql);
    List<Customer> list = qr.list();

和sql语句一样

统计查询

    String hql="select count(*) from Customer ";
    String hq2="select sum(*) from Customer ";
    String hq3="select avg(*) from Customer ";
    String hq4="select max(*) from Customer ";
    String hq5="select min(*) from Customer ";
    Query qr = session.createQuery(hql);
    Number uniqueResult = (Number) qr.uniqueResult();

投影查询

    String hql="select cust_name,cust_id from Customer ";
    Query qr = session.createQuery(hql);
    List<Object[]> list = qr.list(); //list集合中是object数组 一行一个

多表查询

    String hql="from Customer c inner join  c.linkmans";
    String hq2="from Customer c inner join fetch c.linkmans"; //迫切
    String hq3="from Customer c left join fetch c.linkmans"; //左外连接
    Query qr = session.createQuery(hql);
    List<Object[]> list = qr.list(); //不迫切的话是返回这个
    List<Customer> list1 = qr.list(); //迫切的话是返回这个

2、criteria查询(单表查询)

Hibernate自创的无语句面向对象查询

基本查询

        Criteria criteria = session.createCriteria(Customer.class);
        List<Customer> list = criteria.list();

直接就出来了…..

条件查询

        Criteria criteria = session.createCriteria(Customer.class);
        criteria.add(Restrictions.eq("cust_id", 1l));
        Object uniqueResult = criteria.uniqueResult();

其中的Restrictions中是添加查询条件的

>	gt
>=	ge
<	lt
<=	le
=	eq
!=	ne
in	in
between and	between
like	like
is not null	isNotNull
>is null	isNull
or	or
and	and

分页查询

        Criteria criteria = session.createCriteria(Customer.class);
        criteria.setFirstResult(0);  //从0开始
        criteria.setMaxResults(2);

查询总记录数

        Criteria createCriteria = session.createCriteria(Customer.class);
        createCriteria.setProjection(Projections.rowCount());//聚合函数
        Long uniqueResult = (Long)createCriteria.uniqueResult();

排序查询

    Criteria criteria = session.createCriteria(Customer.class);
     criteria.addOrder(Order.asc("cust_id"));
     List list = criteria.list();

2、1离线查询

DetachedCriteria dc = DetachedCriteria.forClass(LinkMan.class);
dc.add(Restrictions.like("lkm_name", "%"+lkm_name+"%"));
        Criteria executableCriteria = dc.getExecutableCriteria(session);
        List<LinkMan> list = executableCriteria.list();

3、原生sql查询(复杂的业务查询)

基本查询

        String sql = "select * from cst_customer";
        SQLQuery createSQLQuery = session.createSQLQuery(sql);
         createSQLQuery.addEntity(Customer.class);
         List<Customer> list = createSQLQuery.list();

条件查询

        String sql = "select * from cst_customer where cst_customer = ?";
        SQLQuery createSQLQuery = session.createSQLQuery(sql);
        createSQLQuery.setParameter(0, 1l);  //设置那个问号的值
        createSQLQuery.addEntity(Customer.class);
        List<Customer> list = createSQLQuery.list();

分页查询

        String sql = "select * from cst_customer limit ?,?";
        SQLQuery createSQLQuery = session.createSQLQuery(sql);
        createSQLQuery.setParameter(0, 0);
        createSQLQuery.setParameter(1, 1);
        createSQLQuery.addEntity(Customer.class);

        List<Customer> list = createSQLQuery.list();