hql查询语句

1. 查询整个映射对象所有字段
Java代码
//直接from查询出来的是一个映射对象，即：查询整个映射对象所有字段     
        String hql = "from Users";     
        Query query = session.createQuery(hql);     
             
        List<Users> users = query.list();     
        for(Users user : users){     
            System.out.println(user.getName() + " : " + user.getPasswd() + " : " + user.getId());     
        }     
    
输出结果为：     
name1 : password1 : 1    
name2 : password2 : 2    
name3 : password3 : 3   

//直接from查询出来的是一个映射对象，即：查询整个映射对象所有字段  
        String hql = "from Users";  
        Query query = session.createQuery(hql);  
          
        List<Users> users = query.list();  
        for(Users user : users){  
            System.out.println(user.getName() + " : " + user.getPasswd() + " : " + user.getId());  
        }  
 
输出结果为：  
name1 : password1 : 1 
name2 : password2 : 2 
name3 : password3 : 3 

2.查询单个字段 
Java代码
//查询单个字段     
        String hql = " select name from Users";     
        Query query = session.createQuery(hql);     
             
        List<String> list = query.list();     
        for(String str : list){     
            System.out.println(str);     
        }     
输出结果为：     
name1     
name2     
name3   

//查询单个字段  
        String hql = " select name from Users";  
        Query query = session.createQuery(hql);  
          
        List<String> list = query.list();  
        for(String str : list){  
            System.out.println(str);  
        }  
输出结果为：  
name1  
name2  
name3 

3.查询其中几个字段
 
Java代码
//查询其中几个字段     
        String hql = " select name,passwd from Users";     
        Query query = session.createQuery(hql);     
        //默认查询出来的list里存放的是一个Object数组     
        List<Object[]> list = query.list();     
        for(Object[] object : list){     
            String name = (String)object[0];     
            String passwd = (String)object[1];     
                 
            System.out.println(name + " : " + passwd);     
        }     
输出结果为：     
name1 : password1     
name2 : password2     
name3 : password3   

//查询其中几个字段  
        String hql = " select name,passwd from Users";  
        Query query = session.createQuery(hql);  
        //默认查询出来的list里存放的是一个Object数组  
        List<Object[]> list = query.list();  
        for(Object[] object : list){  
            String name = (String)object[0];  
            String passwd = (String)object[1];  
              
            System.out.println(name + " : " + passwd);  
        }  
输出结果为：  
name1 : password1  
name2 : password2  
name3 : password3 

4.修改默认查询结果(query.list())不以Object[]数组形式返回，以List形式返回

引用
//查询其中几个字段,添加new list(),注意list里的l是小写的。也不需要导入包，这样通过query.list()出来的list里存放的不再是默认的Object数组了，而是List集合了  
        String hql = " select new list(name,passwd) from Users";  
        Query query = session.createQuery(hql);  
        //默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是List集合了  
        List<List> list = query.list();  
        for(List user : list){  
            String name = (String)user.get(0);  
            String passwd = (String)user.get(1);  
              
            System.out.println(name + " : " + passwd);  
        }  
        /** 
        输出结果为： 
         name1 : password1 
        name2 : password2 
        name3 : password3 
         */ 

5.修改默认查询结果(query.list())不以Object[]数组形式返回，以Map形式返回
Java代码
//查询其中几个字段,添加new map(),注意map里的m是小写的。也不需要导入包，这样通过query.list()出来的list里存放的不再是默认的Object数组了，而是map集合了     
        String hql = " select new map(name,passwd) from Users";     
        Query query = session.createQuery(hql);     
        //默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是Map集合了     
        List<Map> list = query.list();     
        for(Map user : list){     
            //一条记录里所有的字段值都是map里的一个元素,key是字符串0,1,2,3....，value是字段值     
            //如果将hql改为：String hql = " select new map(name as username,passwd as password) from Users";,那么key将不是字符串0,1,2...了，而是"username","password"了     
            String name = (String)user.get("0");//get("0");是get(key),注意:0,1,2...是字符串，而不是整形     
            String passwd = (String)user.get("1");     
                 
            System.out.println(name + " : " + passwd);     
        }     
        /**   
        输出结果为：   
         name1 : password1   
        name2 : password2   
        name3 : password3   
         */   

//查询其中几个字段,添加new map(),注意map里的m是小写的。也不需要导入包，这样通过query.list()出来的list里存放的不再是默认的Object数组了，而是map集合了  
        String hql = " select new map(name,passwd) from Users";  
        Query query = session.createQuery(hql);  
        //默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是Map集合了  
        List<Map> list = query.list();  
        for(Map user : list){  
            //一条记录里所有的字段值都是map里的一个元素,key是字符串0,1,2,3....，value是字段值  
            //如果将hql改为：String hql = " select new map(name as username,passwd as password) from Users";,那么key将不是字符串0,1,2...了，而是"username","password"了  
            String name = (String)user.get("0");//get("0");是get(key),注意:0,1,2...是字符串，而不是整形  
            String passwd = (String)user.get("1");  
              
            System.out.println(name + " : " + passwd);  
        }  
        /** 
        输出结果为： 
         name1 : password1 
        name2 : password2 
        name3 : password3 
         */ 
6.修改默认查询结果(query.list())不以Object[]数组形式返回，以Set形式返回,但是因为Set里是不允许有重复的元素，所以:username和password的值不能相同。只需将hql改为：String hql = " select new set(name,passwd) from Users";

7.修改默认查询结果(query.list())不以Object[]数组形式返回，以自定义类型返回

自定义类：
 
Java代码
package com.domain;     
    
public class MyUser {     
    
    private String username;     
    private String password;     
//因为：String hql = " select new  com.domain.MyUser(name,passwd) from Users";所以必须要有接受2个参数的构造函数     
    public MyUser(String username,String password){     
        this.username = username;     
        this.password = password;     
    }     
         
    public String getUsername() {     
        return username;     
    }     
    public void setUsername(String username) {     
        this.username = username;     
    }     
    public String getPassword() {     
        return password;     
    }     
    public void setPassword(String password) {     
        this.password = password;     
    }     
         
         
}   

package com.domain;  
 
public class MyUser {  
 
    private String username;  
    private String password;  
//因为：String hql = " select new  com.domain.MyUser(name,passwd) from Users";所以必须要有接受2个参数的构造函数  
    public MyUser(String username,String password){  
        this.username = username;  
        this.password = password;  
    }  
      
    public String getUsername() {  
        return username;  
    }  
    public void setUsername(String username) {  
        this.username = username;  
    }  
    public String getPassword() {  
        return password;  
    }  
    public void setPassword(String password) {  
        this.password = password;  
    }  
      
      
} 

 
Java代码
//通过query.list()出来的list里存放的不再是默认的Object数组了,而是自定义的类MyUser,必须加包名，String hql = "from Users";中的Users类也是必须加包名的，但是因为再Users.hbm.xml里<hibernate-mapping auto-import="true"> auto-import默认值为true（所以auto-import属性也可以不写）,自动导入了     
        String hql = " select new  com.domain.MyUser(name,passwd) from Users";     
        Query query = session.createQuery(hql);     
        //默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是MyUser对象了     
        List<MyUser> myUsers = query.list();     
        for(MyUser myUser : myUsers){     
            String name = myUser.getUsername();     
            String passwd = myUser.getPassword();     
            System.out.println(name + " : " + passwd);     
        }     
        /**   
        输出结果为：   
        name1 : password1   
        name2 : password2   
        name3 : password3   
         */   

//通过query.list()出来的list里存放的不再是默认的Object数组了,而是自定义的类MyUser,必须加包名，String hql = "from Users";中的Users类也是必须加包名的，但是因为再Users.hbm.xml里<hibernate-mapping auto-import="true"> auto-import默认值为true（所以auto-import属性也可以不写）,自动导入了  
        String hql = " select new  com.domain.MyUser(name,passwd) from Users";  
        Query query = session.createQuery(hql);  
        //默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是MyUser对象了  
        List<MyUser> myUsers = query.list();  
        for(MyUser myUser : myUsers){  
            String name = myUser.getUsername();  
            String passwd = myUser.getPassword();  
            System.out.println(name + " : " + passwd);  
        }  
        /** 
        输出结果为： 
        name1 : password1 
        name2 : password2 
        name3 : password3 
         */ 

8：条件查询
Java代码
//条件查询，参数索引值从0开始，索引位置。通过setString,setParameter设置参数     
        String hql = "from Users where name=? and passwd=?";     
        Query query = session.createQuery(hql);     
        //第1种方式     
//      query.setString(0, "name1");     
//      query.setString(1, "password1");     
        //第2种方式     
        query.setParameter(0, "name1",Hibernate.STRING);     
        query.setParameter(1, "password1",Hibernate.STRING);     
        List<Users> list = query.list();     
        for(Users users : list){     
            System.out.println(users.getId());     
        }    

//条件查询，参数索引值从0开始，索引位置。通过setString,setParameter设置参数  
        String hql = "from Users where name=? and passwd=?";  
        Query query = session.createQuery(hql);  
        //第1种方式  
//      query.setString(0, "name1");  
//      query.setString(1, "password1");  
        //第2种方式  
        query.setParameter(0, "name1",Hibernate.STRING);  
        query.setParameter(1, "password1",Hibernate.STRING);  
        List<Users> list = query.list();  
        for(Users users : list){  
            System.out.println(users.getId());  
        }            
Java代码
//条件查询，自定义索引名(参数名):username,:password.通过setString,setParameter设置参数     
        String hql = "from Users where name=:username and passwd=:password";     
        Query query = session.createQuery(hql);     
        //第1种方式     
//      query.setString("username", "name1");     
//      query.setString("password", "password1");     
        //第2种方式,第3个参数确定类型     
        query.setParameter("username", "name1",Hibernate.STRING);     
        query.setParameter("password", "password1",Hibernate.STRING);     
        List<Users> list = query.list();     
        for(Users users : list){     
            System.out.println(users.getId());     
        }   

//条件查询，自定义索引名(参数名):username,:password.通过setString,setParameter设置参数  
        String hql = "from Users where name=:username and passwd=:password";  
        Query query = session.createQuery(hql);  
        //第1种方式  
//      query.setString("username", "name1");  
//      query.setString("password", "password1");  
        //第2种方式,第3个参数确定类型  
        query.setParameter("username", "name1",Hibernate.STRING);  
        query.setParameter("password", "password1",Hibernate.STRING);  
        List<Users> list = query.list();  
        for(Users users : list){  
            System.out.println(users.getId());  
        } 

Java代码
//条件查询,通过setProperties设置参数     
        String hql = "from Users where name=:username and passwd=:password";     
        Query query = session.createQuery(hql);     
        //MyUser类的2个属性必须和:username和:password对应     
        MyUser myUser = new MyUser("name1","password1");     
        query.setProperties(myUser);     
        List<Users> list = query.list();     
        for(Users users : list){     
            System.out.println(users.getId());     
        }