HQL查询语言的使用介绍_数据库其他教程-查字典教程网

摘要：HQL查询依赖于Query类，每个Query实例对应一个查询对象，使用HQL查询按如下步骤进行：1.获取HibernateSession对象...

HQL查询依赖于Query类，每个Query实例对应一个查询对象，使用HQL查询按如下步骤进行：

1.获取Hibernate Session对象

2.编写HQL语句

3.以HQL语句作为参数，调用Session的createQuery方法创建查询对象

4.如果HQL语句包含参数，则调用Query的setXxx方法为参数赋值

5.调用Query独享的list()或uniqueResult()方法返回查询结果列表

简单的例子：

复制代码代码如下:

@SuppressWarnings("deprecation")

public class HibernateUtil {

private static final SessionFactory sessionFactory;

static {

sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();

}

public static Session getOpenSession() {

return sessionFactory.openSession();

}

public static Session getCurrentSession() {

return sessionFactory.getCurrentSession();

}

@Entity

public class Employee {

private Integer id;

private String name;

private Integer age;

@Id

@GeneratedValue

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

@Basic

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

@Basic

public Integer getAge() {

return age;

}

public void setAge(Integer age) {

this.age = age;

}

public String toString() {

return "id:" + id + " " + "name:" + name + " " + "age:" + age;

}

@SuppressWarnings("all")

public class HQLDemo {

@Test

public void testHQL() {

Session session = HibernateUtil.getOpenSession();

List<Employee> employeeList = session.createQuery("from Employee as e").list();

for(Employee e : employeeList)

System.out.println(e);

}

@Test

public void testHQLHasParameter() {

Session session = HibernateUtil.getOpenSession();

List<Employee> employeeList = session.createQuery("from Employee as e where e.name = :personName").setString("personName", "xujianguo").list();

for(Employee e : employeeList)

System.out.println(e);

}

HQL查询的from子句：

from是最简单的HQL语句，也是最基本的HQL语句，from关键字后紧跟持久化类的类名，如：

from Employee表名从Employee类中选出全部的实例

不过我们常用的是这样做：

from employee as e这个e就是Employee的别名，也就是实例名，推荐这么写。

HQL查询的select子句：

select子句用于选择指定的属性或直接选择某个实体，当然select选择的属性必须是from后持久化类包含的属性，如：

select e.name from Employee as eselect可以选择任意属性，即不仅可以选择持久化类的直接属性，还可以选择组件属性包含的属性，如：

select e.name.firstName from Employee as eHQL查询的聚集函数：

聚集函数：

avg：计算属性的平均值

count：统计选择对象的数量

max：统计属性值的最大值

min：统计属性值的最小值

sum：计算属性值的总和

如：

复制代码代码如下:

select count(*) from Employee as e @Test

public void testHQLFunction() {

Session session = HibernateUtil.getOpenSession();

System.out.println(session.createQuery("select count(*) from Employee as e").uniqueResult());

}

多态查询：

HQL不仅会查询出该持久化类的全部实例，还会查询出该类的子类的全部实例，前提是存在继承映射。

HQL查询的where子句：

where子句主要用于筛选选中的结果，缩小选择的范围，如：

复制代码代码如下:

from employee as e where e.name like "xjg%" @Test

public void testHQLWhere() {

Session session = HibernateUtil.getOpenSession();

List<Employee> employeeList = session.createQuery("from Employee as e where e.name like 'zhou%'").list();

for(Employee e : employeeList)

System.out.println(e);

}

order by子句：

查询返回结合可以根据类或组件属性的任何属性进行排序，还可以使用asc或desc关键字指定升序或者降序，如：

from Employee as e order by e.name desc

子查询：

子查询中就是查询语句中还有查询语句，如：

复制代码代码如下:

from Employee as e where e.age > (select p.age from Person as p) @Test

public void testHQLChildQuery() {

Session session = HibernateUtil.getOpenSession();

List<Employee> employeeList = session.createQuery("from Employee as e where e.age > (select e1.age from Employee as e1 where e1.name = 'xujianguo')").list();

for(Employee e : employeeList)

System.out.println(e);

}

[code]

命名查询：

HQL查询还支持将查询所用的HQL语句放入配置文件中，而不是代码中，在Hibernate映射文件的<hibernate-mapping>元素中使用<query>子元素来定义命名查询，这个<query>元素只需指定一个name属性，指定该命名查询的名字，如：

[code]

from Employee as e

Session里提供了一个getNamedQuery(String name)方法，该方法用于创建一个Query对象，一旦获得Query对象，剩下的工作就跟前面的一样了。

复制代码代码如下:

@Test

public void testHQLNamedQuery() {

Session session = HibernateUtil.getOpenSession();

List<Employee> employeeList = session.getNamedQuery("query").list();

for(Employee e : employeeList)

System.out.println(e);

}

HQL 查询语句

/**

package com.b510.example;

import java.util.Iterator;

import java.util.List;

import java.util.Map;

import org.hibernate.Criteria;

import org.hibernate.FetchMode;

import org.hibernate.Query;

import org.hibernate.Session;

/**

* @author XHW

* @date 2011-6-18

public class HibernateTest {

/**

* @param args

public static void main(String[] args) {

HibernateTest test = new HibernateTest();

test.where();

test.function();

test.update();

test.jiaoChaCheck();

test.innerJoin();

test.QBC();

test.leftOuterJoin();

test.rightOuterJoin();

}

public void where() {

// 使用where查询

Session session = HibernateSessionFactoryUtil.getSessionFactory()

.openSession();

session.beginTransaction();

Query query = session

.createQuery("from User where id not between 200 and 2000");

List<User> list = query.list();

for (User user : list) {

System.out.println(user.getId() + user.getUsername());

}

// 投影查询中使用where子句

query = session.createQuery("select username from User where id=2");

List<String> listname = query.list();

for (String name : listname) {

System.out.println(name);

}

// in查询

query = session

.createQuery("from User where username in ('Hongten','Hanyuan','dfgd')");

List<User> listin = query.list();

for (User user : listin) {

System.out.println(user.getId() + user.getUsername());

}

// like查询

query = session.createQuery("from User where username not like 'Hon%'");

List<User> listlike = query.list();

for (User user : listlike) {

System.out.println(user.getId() + user.getUsername());

}

// null查询

query = session.createQuery("from User where password is null");

List<User> listnull = query.list();

for (User user : listnull) {

System.out.println(user.getId() + user.getUsername());

}

// and查询

query = session

.createQuery("from User where password is not null and id<5");

List<User> listand = query.list();

for (User user : listand) {

System.out.println(user.getId() + user.getUsername()

+ user.getPassword());

}

// order by

query = session.createQuery("from User order by username,id desc");

List<User> listorderby = query.list();

for (User user : listorderby) {

System.out.println(user.getId() + user.getUsername());

}

// 使用"?"号作为参数占位符，一条HQL语句中可以使用多个？

// query.setInteger(0,2)

// query.setString(0,"Hongten")

query = session

.createQuery("select username from User where username=?");

query.setString(0, "Hongten");

List<String> listwenhao = query.list();

for (String name : listwenhao) {

System.out.println(name);

}

session.getTransaction().commit();

}

public void function() {// 把大写字母转化为小写字母

// 作用可以用在：比如在一个用户注册的程序中，大小写不容易区分，但是全部转化为小写后就可以很容易进行比较

Session session = HibernateSessionFactoryUtil.getSessionFactory()

.openSession();

session.beginTransaction();

// 输出原始的数据

Query query = session.createQuery("select username from User");

List<String> list = query.list();

for (String name : list) {

System.out.println(name);

}

System.out.println("-------------------------------------------");

// 输出的数据全部转化为小写

query = session.createQuery("select lower(username) from User");

List<String> listChange = query.list();

for (String name : listChange) {

System.out.println(name);

}

session.getTransaction().commit();

}

public void update() {

Session session = HibernateSessionFactoryUtil.getSessionFactory()

.openSession();

session.beginTransaction();

Query query = session

.createQuery("update User set username='洪伟1231' where id=?");

query.setInteger(0, 3);

int rowCount = query.executeUpdate();

System.out.println(rowCount);

session.getTransaction().commit();

}

public void operateProfile() {// 对profile这个类执行HQL语句操作

Session session = HibernateSessionFactoryUtil.getSessionFactory()

.openSession();

session.beginTransaction();

// 执行查询操作

Query query = session.createQuery("from Profile");

List<Profile> list = query.list();

for (Profile profile : list) {

System.out.println(profile.getId() + profile.getEmail()

+ profile.getAddress() + profile.getMobile()

+ profile.getPostcode());

}

// 执行删除操作

query = session.createQuery("delete from Profile where id=?");

query.setInteger(0, 3);

int rowCount = query.executeUpdate();

System.out.println(rowCount);

session.getTransaction().commit();

}

public void jiaoChaCheck() {//交叉查询

//这种方法查询出来的结果是笛卡尔积，对于我们开发中没有多大用处

Session session = HibernateSessionFactoryUtil.getSessionFactory()

.openSession();

session.beginTransaction();

Query query=session.createQuery("from User,Profile");

List<Object[]> list=query.list();

for(Object[] values:list){

User user=(User)values[0];

System.out.print("ID :"+user.getId()+",UserName:"+user.getUsername()+",Password:"+user.getPassword());

Profile profile=(Profile)values[1];

System.out.println(profile.getEmail()+profile.getMobile()+profile.getAddress()+profile.getPostcode());

}

session.getTransaction().commit();

}

public void innerJoin(){//内连接查询

/**

* 下面三种hql语句都是可以得到相同的结果

* String hql="select p from Profile as p inner join p.user";

* 在下面的hql语句中加入"fetch"后，此hql语句变为了"迫切HQL"语句，这样的查询效率要比上面的hql语句要高

* String hql="select p from Profile as p inner join fetch p.user";

* String hql="select p from Profile p,User u where p.user=u";

* String hql="select p from Profile p,User u where p.user.id=u.id";

Session session = HibernateSessionFactoryUtil.getSessionFactory()

.openSession();

session.beginTransaction();

String hql="select p from Profile as p inner join fetch p.user";

//String hql="select p from Profile p,User u where p.user=u";

//String hql="select p from Profile p,User u where p.user.id=u.id";

Query query=session.createQuery(hql);

List<Profile> list=query.list();

for(Profile p:list){

System.out.println("ID:"+p.getUser().getId()+" Username: "+p.getUser().getUsername()+" Email: "+p.getEmail()+", Address: "+p.getAddress());

}

session.getTransaction().commit();

}

public void QBC(){//QBC中实现内连接查询

Session session=HibernateSessionFactoryUtil.getSessionFactory().openSession();

session.beginTransaction();

Criteria criteria=session.createCriteria(Profile.class).createCriteria("user");

List<Profile> list=criteria.list();

for(Profile p:list){

System.out.println("ID:"+p.getUser().getId()+" Username: "+p.getUser().getUsername()+" Email: "+p.getEmail()+", Address: "+p.getAddress());

}

//QBC中实现外连接

System.out.println("##################################################");

criteria=session.createCriteria(Profile.class).setFetchMode("user", FetchMode.JOIN);

List<Profile> listp=criteria.list();

for(Profile p:list){

System.out.println("ID:"+p.getUser().getId()+" Username: "+p.getUser().getUsername()+" Email: "+p.getEmail()+", Address: "+p.getAddress());

}

session.getTransaction().commit();

}

public void leftOuterJoin(){//左外连接

/**

* String hql="select p from Profile p left outer join p.user order by p.user.id";

* 在下面的hql语句中加入"fetch"后，此hql语句变为了"迫切HQL"语句，这样的查询效率要比上面的hql语句要高

* String hql="select p from Profile p left outer join fetch p.user order by p.user.id";

* String hqlu="select u from User u left outer join u.profiles";

* 在下面的hql语句中加入"fetch"后，此hql语句变为了"迫切HQL"语句，这样的查询效率要比上面的hql语句要高

* String hqlu="select u from User u left outer join fetch u.profiles";

Session session=HibernateSessionFactoryUtil.getSessionFactory().getCurrentSession();

session.beginTransaction();

String hql="select p from Profile p left outer join fetch p.user order by p.user.id";

Query query=session.createQuery(hql);

List<Profile> list=query.list();

for(Profile p:list){

System.out.println("ID:"+p.getUser().getId()+" Username: "+p.getUser().getUsername()+" Email: "+p.getEmail()+", Address: "+p.getAddress());

}

System.out.println("-------------------------------------");

String hqlu="select u from User u left outer join fetch u.profiles";

query=session.createQuery(hqlu);

List<User> listu=query.list();

for(User u:listu){

System.out.println(u.getId()+u.getUsername()+u.getProfiles());

}

session.getTransaction().commit();

}

public void rightOuterJoin(){//右外连接

Session session=HibernateSessionFactoryUtil.getSessionFactory().getCurrentSession();

session.beginTransaction();

String hql="select u from User u right outer join u.profiles order by u.id";

Query query=session.createQuery(hql);

List<User> listu=query.list();

for(User user:listu){

System.out.println(user.getId()+user.getUsername()+user.getProfiles());

}

session.getTransaction().commit();

}

结果：

log4j:WARN No appenders could be found for logger (org.hibernate.cfg.Environment).

log4j:WARN Please initialize the log4j system properly.

Hibernate:

select

user0_.id as id0_,

user0_.username as username0_,

user0_.password as password0_

from

users.user user0_

where

user0_.id not between 200 and 2000

1hongten

2hanyuan

3hongwei

4mingliu

5shouzhang

Hibernate:

select

user0_.username as col_0_0_

from

users.user user0_

where

user0_.id=2

hanyuan

Hibernate:

select

user0_.id as id0_,

user0_.username as username0_,

user0_.password as password0_

from

users.user user0_

where

user0_.username in (

'Hongten' , 'Hanyuan' , 'dfgd'

)

1hongten

2hanyuan

Hibernate:

select

user0_.id as id0_,

user0_.username as username0_,

user0_.password as password0_

from

users.user user0_

where

user0_.username not like 'Hon%'

2hanyuan

4mingliu

5shouzhang

Hibernate:

select

user0_.id as id0_,

user0_.username as username0_,

user0_.password as password0_

from

users.user user0_

where

user0_.password is null

Hibernate:

select

user0_.id as id0_,

user0_.username as username0_,

user0_.password as password0_

from

users.user user0_

where

(

user0_.password is not null

)

and user0_.id<5

1hongten123

2hanyuan5645645

3hongwei5645645

4mingliu5645645

Hibernate:

select

user0_.id as id0_,

user0_.username as username0_,

user0_.password as password0_

from

users.user user0_

order by

user0_.username,

user0_.id desc

2hanyuan

1hongten

3hongwei

4mingliu

5shouzhang

Hibernate:

select

user0_.username as col_0_0_

from

users.user user0_

where

user0_.username=?

hongten

Hibernate:

select

user0_.username as col_0_0_

from

users.user user0_

hongten

hanyuan

hongwei

mingliu

shouzhang

-------------------------------------------

Hibernate:

select

lower(user0_.username) as col_0_0_

from

users.user user0_

hongten

hanyuan

hongwei

mingliu

shouzhang

Hibernate:

update

users.user

set

username='Hongwei1231'

where

id=?

Hibernate:

select

user0_.id as id0_0_,

profile1_.id as id1_1_,

user0_.username as username0_0_,

user0_.password as password0_0_,

profile1_.user_id as user2_1_1_,

profile1_.email as email1_1_,

profile1_.phone as phone1_1_,

profile1_.mobile as mobile1_1_,

profile1_.address as address1_1_,

profile1_.postcode as postcode1_1_

from

users.user user0_,

users.profile profile1_

ID :1,UserName:hongten,Password:123hongtenzone@foxmail.com45464Guangzhoushi65465

ID :1,UserName:hongten,Password:123hanyuan@foxmail.com45648255GuangzhoushiDianbian65465

ID :2,UserName:hanyuan,Password:5645645hongtenzone@foxmail.com45464Guangzhoushi65465

ID :2,UserName:hanyuan,Password:5645645hanyuan@foxmail.com45648255GuangzhoushiDianbian65465

ID :3,UserName:Hongwei1231,Password:5645645hongtenzone@foxmail.com45464Guangzhoushi65465

ID :3,UserName:Hongwei1231,Password:5645645hanyuan@foxmail.com45648255GuangzhoushiDianbian65465

ID :4,UserName:mingliu,Password:5645645hongtenzone@foxmail.com45464Guangzhoushi65465

ID :4,UserName:mingliu,Password:5645645hanyuan@foxmail.com45648255GuangzhoushiDianbian65465

ID :5,UserName:shouzhang,Password:5645645hongtenzone@foxmail.com45464Guangzhoushi65465

ID :5,UserName:shouzhang,Password:5645645hanyuan@foxmail.com45648255GuangzhoushiDianbian65465

Hibernate:

select

profile0_.id as id1_0_,

user1_.id as id0_1_,

profile0_.user_id as user2_1_0_,

profile0_.email as email1_0_,

profile0_.phone as phone1_0_,

profile0_.mobile as mobile1_0_,

profile0_.address as address1_0_,

profile0_.postcode as postcode1_0_,

user1_.username as username0_1_,

user1_.password as password0_1_

from

users.profile profile0_

inner join

users.user user1_

on profile0_.user_id=user1_.id

ID:1 Username: hongten Email: hongtenzone@foxmail.com, Address: Guangzhoushi

ID:2 Username: hanyuan Email: hanyuan@foxmail.com, Address: GuangzhoushiDianbian

ID:3 Username:Hongwei1231 Email: hanyuan@foxmail.com, Address: GuangzhoushiDianbian

Hibernate:

select

this_.id as id1_1_,

this_.user_id as user2_1_1_,

this_.email as email1_1_,

this_.phone as phone1_1_,

this_.mobile as mobile1_1_,

this_.address as address1_1_,

this_.postcode as postcode1_1_,

user1_.id as id0_0_,

user1_.username as username0_0_,

user1_.password as password0_0_

from

users.profile this_

inner join

users.user user1_

on this_.user_id=user1_.id

ID:1 Username: hongten Email: hongtenzone@foxmail.com, Address: Guangzhoushi

ID:2 Username: hanyuan Email: hanyuan@foxmail.com, Address: GuangzhoushiDianbian

ID:3 Username: Hongwei1231 Email: hanyuan@foxmail.com, Address: GuangzhoushiDianbian

##################################################

Hibernate:

select

this_.id as id1_1_,

this_.user_id as user2_1_1_,

this_.email as email1_1_,

this_.phone as phone1_1_,

this_.mobile as mobile1_1_,

this_.address as address1_1_,

this_.postcode as postcode1_1_,

user2_.id as id0_0_,

user2_.username as username0_0_,

user2_.password as password0_0_

from

users.profile this_

left outer join

users.user user2_

on this_.user_id=user2_.id

ID:1 Username: hongten Email: hongtenzone@foxmail.com, Address: Guangzhoushi

ID:2 Username: hanyuan Email: hanyuan@foxmail.com, Address: GuangzhoushiDianbian

ID:3 Username: 洪伟1231 Email: hanyuan@foxmail.com, Address: GuangzhoushiDianbian

Hibernate:

select

profile0_.id as id1_0_,

user1_.id as id0_1_,

profile0_.user_id as user2_1_0_,

profile0_.email as email1_0_,

profile0_.phone as phone1_0_,

profile0_.mobile as mobile1_0_,

profile0_.address as address1_0_,

profile0_.postcode as postcode1_0_,

user1_.username as username0_1_,

user1_.password as password0_1_

from

users.profile profile0_

left outer join

users.user user1_

on profile0_.user_id=user1_.id

order by

profile0_.user_id

ID:1 Username: hongten Email: hongtenzone@foxmail.com, Address: Guangzhoushi

ID:2 Username: hanyuan Email: hanyuan@foxmail.com, Address: GuangzhoushiDianbian

ID:3 Username: 洪伟1231 Email: hanyuan@foxmail.com, Address: GuangzhoushiDianbian

-------------------------------------

Hibernate:

select

user0_.id as id0_0_,

profiles1_.id as id1_1_,

user0_.username as username0_0_,

user0_.password as password0_0_,

profiles1_.user_id as user2_1_1_,

profiles1_.email as email1_1_,

profiles1_.phone as phone1_1_,

profiles1_.mobile as mobile1_1_,

profiles1_.address as address1_1_,

profiles1_.postcode as postcode1_1_,

profiles1_.user_id as user2_0__,

profiles1_.id as id0__

from

users.user user0_

left outer join

users.profile profiles1_

on user0_.id=profiles1_.user_id

1hongten[com.b510.example.Profile@14eaec9]

2hanyuan[com.b510.example.Profile@569c60]

3Hongwei1231[com.b510.example.Profile@d67067]

4mingliu[]

5shouzhang[]

Hibernate:

select

user0_.id as id0_,

user0_.username as username0_,

user0_.password as password0_

from

users.user user0_

right outer join

users.profile profiles1_

on user0_.id=profiles1_.user_id

order by

user0_.id

Hibernate:

select

profiles0_.user_id as user2_1_,

profiles0_.id as id1_,

profiles0_.id as id1_0_,

profiles0_.user_id as user2_1_0_,

profiles0_.email as email1_0_,

profiles0_.phone as phone1_0_,

profiles0_.mobile as mobile1_0_,

profiles0_.address as address1_0_,

profiles0_.postcode as postcode1_0_

from

users.profile profiles0_

where

profiles0_.user_id=?

1hongten[com.b510.example.Profile@10c0f66]

Hibernate:

select

profiles0_.user_id as user2_1_,

profiles0_.id as id1_,

profiles0_.id as id1_0_,

profiles0_.user_id as user2_1_0_,

profiles0_.email as email1_0_,

profiles0_.phone as phone1_0_,

profiles0_.mobile as mobile1_0_,

profiles0_.address as address1_0_,

profiles0_.postcode as postcode1_0_

from

users.profile profiles0_

where

profiles0_.user_id=?

2hanyuan[com.b510.example.Profile@e265d0]

Hibernate:

select

profiles0_.user_id as user2_1_,

profiles0_.id as id1_,

profiles0_.id as id1_0_,

profiles0_.user_id as user2_1_0_,

profiles0_.email as email1_0_,

profiles0_.phone as phone1_0_,

profiles0_.mobile as mobile1_0_,

profiles0_.address as address1_0_,

profiles0_.postcode as postcode1_0_

from

users.profile profiles0_

where

profiles0_.user_id=?

3Hongwei1231[com.b510.example.Profile@8997d1]