Hibernate-04

hql查询语法

　　

查询：
public class dome{
      session session = hibernaeuitls.opensession();
      transaction tx = session.begintransaction();
      //待执行执行sql
　　　 string hql = "from user";
　　   string hqls = "from cn.it.user"//类路径下
　　　//排序查询
　　　 string orderby = "from cn.it.user order by  u_id asc";
　　　 string orderby2 = "from cn.it.user order by  u_id desc";
　　　//条件查询
　　　 string wherehql = "from cn.it.user where u_id = ?";
　　　 string wherehql = "from cn.it.user where u_id =:id";

　　　　

      //创建查询对象
      query query = session.createquery(hql);
      list list = query.list();
      system.out.println(list);
      //提交事务
       tx.commit();     
      //关闭session
       session.close();
    }

//分页
public void fun4(){
        session session = hibernateutils.opensession();
        transaction tx = session.begintransaction();
        //----------------------------------------------------
        string hql1 = " from  cn.it.user  ";//完整写法
        
        query query = session.createquery(hql1);
        
        //limit ?,?
        // (当前页数-1)*每页条数
        query.setfirstresult(4);
        query.setmaxresults(5);
        
        list list = query.list();
        
        system.out.println(list);
        //----------------------------------------------------
        tx.commit();
        session.close();
        
    }

聚合查询：count，sum ，svg，max，min

public void fun5(){
        session session = hibernateutils.opensession();
        transaction tx = session.begintransaction();
        //----------------------------------------------------
        string hql1 = " select count(*) from  cn.it.user ";
        string hql2 = " select sum(cust_id) from  cn.it.user  ";
        string hql3 = " select avg(cust_id) from  cn.it.user  ";
        string hql4 = " select max(cust_id) from  cn.it.user  ";
        string hql5 = " select min(cust_id) from  cn.it.user  ";
        
        query query = session.createquery(hql5);
        
        number number  = (number) query.uniqueresult();
        
        system.out.println(number);
        //----------------------------------------------------
        tx.commit();
        session.close();
        
    }

 

 

投影查询

public void fun6(){
        session session = hibernateutils.opensession();
        transaction tx = session.begintransaction();
        //----------------------------------------------------//
        string hql1 = " select u_name from  cn.it.user  ";
        string hql2 = " select u_name,u_id from  cn.it.user  ";
        string hql3 = " select new user(u_id,u_name) from  cn.it.user  ";
        
        query query = session.createquery(hql3);
        
        list list = query.list();
        
        system.out.println(list);
        
        //----------------------------------------------------//
        tx.commit();
        session.close();
        
    }

 

criteria查询语法:和hql一样的也是面向对象的orm查询

简单查询：
public void fun(){
     session session = hibernateutils.opensession();
     transaction tx = session.begintransaction();
    //--------------------------------------------------
     user c = session.createcritreria(user.class);
     list <user> list = c.list():
    system.out.println(list);
    //--------------------------------------------------
     tx.commit();
    session.clone();        
}

#条件查询
----------
//---------------------------------------------------------------
criteria c = session.createcriteria(user.clsss);
//添加
c.add(restrictions.eq("u_id",32));
list<user> list = c.list();
system.out.println(list);

//---------------------------------------------------------------
tx.commit();
session.close();

#分页
----------
//---------------------------------------------------------------
criteria c = session.createcriteria(user.clsss);

c.setfirstresult(1);
c.setmaxresult(4);


list<user> list = c.list();
system.out.println(list);

//---------------------------------------------------------------
tx.commit();
session.close();

#排序

//---------------------------------------------------------------
criteria c = session.createcriteria(user.clsss);

c.addorder(order.asc("u_id"));
//c.addorder(order.desc("u_id"));


list<user> list = c.list();
system.out.println(list);

//---------------------------------------------------------------
tx.commit();
session.close();

统计

//---------------------------------------------------------------
criteria c = session.createcriteria(user.clsss);

c.setprojection(projections.rowcount());


list<user> list = c.list();
system.out.println(list);

//---------------------------------------------------------------
tx.commit();
session.close();

离线criteria

public void fun(){
     detachedcriteria dc = detachedcriteria.forclass(user.class);
     dc.add(restrictions.ideq(61));
    //-------------------------------------------------------------   
     session session = hibernateutils.opensession();
     transaction tx = session.begintransaction();
     //-----------------------------------------------------------
     criteria c = dc.getexecutablecriteria(session);   
     list list = c.list();
     system.out.println(list);
 
    //-------------------------------------------------------------
     tx.commit();
     session.close();
}        

 

查询优化