@Test
        public void query(){
            // sql : select 列名    from 表明;
            // hql : select 屬性名 from 類名; 
            //       select 別名.屬性 from 類名 as 別名;
            String hql = "from User";
            Query query = session.createQuery(hql);
            List list = query.list();
            System.out.println(list);
        }
 

查詢多個屬性時,返回的是對象數組;
其中對象中第一個為id,第二個元素為pwd

String hql = "select id,pwd from user";
    List<Object[]> list = session.createQuery(hql);

uniqueResult() 查詢一條.

String hql = "select count(*) from User";
          Query query = session.createQuery(hql);
          Object uniqueResult = query.uniqueResult();
 

分頁查詢
setFirstResult(N):查詢的第N條數據編號
setMaxResults(20):查詢的數據總量

String hql = "from User";

    Query query = session.createQuery(hql);
    query.setFirstResult(1);
    query.setMaxResults(20);
    List list = query.list();

    System.out.println(list);

可變參數查詢(占位符)

String hql = "from User where name = ? and age = ?";
        Query query = session.createQuery(hql);
        query.setParameter(0, "fy"); // query.setString(1, "fy");
        query.setParameter(1, "18");
        List list = query.list();
        System.out.println(list);

        常用寫法:
        String hql = "from User where name = :name and age = :age";
        query.setString("name", "fy");
        query.setString("age", "18");
 

聚合函數

count       返回的結果：Long
max/min     返回的結果：原始類型
sum         返回的結果：Long或Double
avg         返回的結果：Double

由於返回結果通常為單一數據，常使用uniqueResult()獲得結果
分組查詢

Query q = s.createQuery("select address,count(address) from UserModel group by address");

排序查詢

Query q = s.createQuery("from UserModel order by age desc");

投影數據封裝
前提: 對象模型中需要有UserModel(age,name)構造方法,參數順序必須與hql中投影一致.

s.createQuery("select new UserModel(age,name) from UserModel");
———華麗分割——–hibernate 的Criteria
Criteria查詢又名QBC查詢，以面向對象格式完成查詢操作，實現真正的自動生成SQL語句.
查詢單一屬性: 返回該屬性類型

Criteria criteria = session.createCriteria(User.class);
      //Hibernate: select this_.name as y0_ from userdata this_
      方式一:
      Property pro = Property.forName("name");
      criteria.setProjection(pro);
      方式二:
      PropertyProjection property = Projections.property("name");
      criteria.setProjection(property);

      List list = criteria.list();

criteria.setProjection(property);不能重復復制,如果重復設置的話會把上一個覆蓋.
查詢多個屬性: 查詢結果為對象數組

1.聲明查詢屬性的列表對象
       ProjectionList li = Projections.projectionList();
       2.聲明要查詢的屬性
       PropertyProjection name = Projections.property("name");
       PropertyProjection id = Projections.property("id");
       3.將查詢的屬性放入屬性列表
       li.add(id);
       li.add(name);
       4.為criteria設置屬性列表
       criteria.setProjection(li);
       List<Object[]> list = criteria.list();

聚合函數

count:   行數
            Projection condition = Projections.rowCount();  

        max/min: 最大值    
            Projection conditionMax = Projections.max("age");       
            Projection conditionMin = Projections.min("age");       
        Sum  :   和
            Projection conditionSum = Projections.sum("age");       
        Avg :    平均數
            Projection conditionAvg = Projections.avg("age");

分組查詢

Projections.groupProperty("address");

排序

criteria.addOrder(Order.desc("age"));
     criteria.addOrder(Order.asc("age"));

條件查詢.
條件查詢使用

Restrictions.eq 等於= Restrictions.allEq  使用Map,使用key/value進行多個等於的判斷
   Restrictions.gt 大於>
   Restrictions.ge 大於等於>=
   Restrictions.lt 小於<
   Restrictions.le 小於等於<=
   Restrictions.between    對應sql的between子句
   Restrictions.like   對應sql的like子句
   Restrictions.in 對應sql的in子句
   Restrictions.and    and 關系
   Restrictions.or or關系
   Restrictions.sqlRestriction Sql限定查詢

   Criterion c = Restrictions.allEq(arg0);
   criteria.add(c);

離線查詢 (DetachedCriteria)
將查詢字段在view層封裝到DetachedCriteria對象中,
DetachedCriteria不依賴session即可創建. 這樣session就不會暴露在view以及業務層.最後在Controller層,通過session把DetachedCriteria裝換成可以執行查詢的Criteria.

表現層:
    DetachedCriteria dc = DetachedCriteria.forClass(UserModel.class);
    dc.add(Restrictions.like("address", "%"+address+"%"));
    dc.add(Restrictions.between("age", age1, age2));
    數據層:
    Criteria c = dc.getExecutableCriteria(session);
    c.list();

———華麗分割——–hibernate 的SQLQuery查詢
直接執行原生的sql語句.

String sql = "select * from tbl_user";
    SQLQuery sq = session.createSQLQuery(sql);
    sq.list(); //uniqueResult()

通過別名為查詢的模型數據進行封裝.

String sql = "select u.* from tbl_user u";
   SQLQuery sq = session.createSQLQuery(sql);
   sq.addEntity("別名",模型類.class); // sq.addEntity("u",模型類.class);

———華麗分割——–配置型SQL/HQL語句
1.在hbm.xml的hibernate-mapping元素中配置

Hibernate 入門----Query,Criteria,SQLQuery