HQL语句中不可以出现与表有关的内容，而是对象的属性
实体类（注意配置文件）：
package domain;import java.util.HashSet;import java.util.Set;//客户实体public class Customer { ???????private Long cust_id; ???private String cust_name; ???private String cust_source; ???private String cust_industry; ???private String cust_level; ???private String cust_linkman; ???private String cust_phone; ???private String cust_mobile; ???//使用set集合,表达一对多关系 ???private Set<LinkMan> linkMens = new HashSet<LinkMan>(); ???public Set<LinkMan> getLinkMens() { ???????return linkMens; ???} ???public void setLinkMens(Set<LinkMan> linkMens) { ???????this.linkMens = linkMens; ???} ???public Long getCust_id() { ???????return cust_id; ???} ???public void setCust_id(Long cust_id) { ???????this.cust_id = cust_id; ???} ???public String getCust_name() { ???????return cust_name; ???} ???public void setCust_name(String cust_name) { ???????this.cust_name = cust_name; ???} ???public String getCust_source() { ???????return cust_source; ???} ???public void setCust_source(String cust_source) { ???????this.cust_source = cust_source; ???} ???public String getCust_industry() { ???????return cust_industry; ???} ???public void setCust_industry(String cust_industry) { ???????this.cust_industry = cust_industry; ???} ???public String getCust_level() { ???????return cust_level; ???} ???public void setCust_level(String cust_level) { ???????this.cust_level = cust_level; ???} ???public String getCust_linkman() { ???????return cust_linkman; ???} ???public void setCust_linkman(String cust_linkman) { ???????this.cust_linkman = cust_linkman; ???} ???public String getCust_phone() { ???????return cust_phone; ???} ???public void setCust_phone(String cust_phone) { ???????this.cust_phone = cust_phone; ???} ???public String getCust_mobile() { ???????return cust_mobile; ???} ???public void setCust_mobile(String cust_mobile) { ???????this.cust_mobile = cust_mobile; ???} ???@Override ???public String toString() { ???????return "Customer [cust_id=" + cust_id + ", cust_name=" + cust_name + "]"; ???}}抽取工具类：
package utils;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;public class HibernateUtils { ???private static SessionFactory sf; ???????static{ ???????//1 创建,调用空参构造 ???????Configuration conf = new Configuration().configure(); ???????//2 根据配置信息,创建 SessionFactory对象 ????????sf = conf.buildSessionFactory(); ???} ???????//获得session => 获得全新session ???public static Session openSession(){ ???????????????//3 获得session ???????????????Session session = sf.openSession(); ???????????????????????????????return session; ???????????} ???//获得session => 获得与线程绑定的session ???public static Session getCurrentSession(){ ???????//3 获得session ???????Session session = sf.getCurrentSession(); ???????????????return session; ???} ???}测试类：
基本语法：
package hql;import java.util.List;import org.hibernate.Query;import org.hibernate.Session;import org.hibernate.Transaction;import org.junit.Test;import domain.Customer;import utils.HibernateUtils;//学习HQL语法public class Demo { ???????//基本语法 ???@Test ???public void fun1(){ ???????Session session = HibernateUtils.openSession(); ???????Transaction tx = session.beginTransaction(); ???????//---------------------------------------------------- ???????String hql = " from ?domain.Customer ";//完整写法 ???????String hql2 = " from ?Customer "; //简单写法 ???????String hql3 = " from java.lang.Object "; //查询所有Object对象，即所有对象 ???????????????Query query = session.createQuery(hql); ???????????????List list = query.list(); ???????????????System.out.println(list); ???????//---------------------------------------------------- ???????tx.commit(); ???????session.close(); ???????????} ???????????@Test ???//排序 ???public void fun2(){ ???????Session session = HibernateUtils.openSession(); ???????Transaction tx = session.beginTransaction(); ???????//---------------------------------------------------- ???????String hql1 = " from ?domain.Customer order by cust_id asc ";//完整写法升序 ???????String hql2 = " from ?domain.Customer order by cust_id desc ";//完整写法降序 ???????????????Query query = session.createQuery(hql2); ???????????????List list = query.list(); ???????????????System.out.println(list); ???????//---------------------------------------------------- ???????tx.commit(); ???????session.close(); ???????????} ???@Test ???//条件查询 ???public void fun3(){ ???????Session session = HibernateUtils.openSession(); ???????Transaction tx = session.beginTransaction(); ???????//---------------------------------------------------- ???????String hql1 = " from ?domain.Customer where cust_id =? ";//？按所有传值 ???????String hql2 = " from ?domain.Customer where cust_id = :id ";//:按名称传值 ???????????????Query query = session.createQuery(hql2); ???????????????//query.setParameter(0, 5l); ???????query.setParameter("id", 5l); ???????????????????????List list = query.list(); ???????????????System.out.println(list); ???????//---------------------------------------------------- ???????tx.commit(); ???????session.close(); ???????????} ???????@Test ???//分页查询 ???public void fun4(){ ???????Session session = HibernateUtils.openSession(); ???????Transaction tx = session.beginTransaction(); ???????//---------------------------------------------------- ???????String hql1 = " from ?domain.Customer ?";//完整写法 ???????????????Query query = session.createQuery(hql1); ???????????????//类似SQL中的limit ?,? ???????// (当前页数-1)*每页条数 ???????query.setFirstResult(0); ???????query.setMaxResults(2); ???????????????List list = query.list(); ???????????????System.out.println(list); ???????//---------------------------------------------------- ???????tx.commit(); ???????session.close(); ???????????} ???????@Test ???//统计查询 ???//count ???计数 ???//sum ????求和 ???//avg ???平均数 ???//max ???//min ???public void fun5(){ ???????Session session = HibernateUtils.openSession(); ???????Transaction tx = session.beginTransaction(); ???????//---------------------------------------------------- ???????String hql1 = " select count(*) from ?domain.Customer ?"; ???????String hql2 = " select sum(cust_id) from ?domain.Customer ?"; ???????String hql3 = " select avg(cust_id) from ?domain.Customer ?"; ???????String hql4 = " select max(cust_id) from ?domain.Customer ?"; ???????String hql5 = " select min(cust_id) from ?domain.Customer ?"; ???????????????Query query = session.createQuery(hql3); ???????????????Number number ?= (Number) query.uniqueResult(); ???????????????System.out.println(number); ???????//---------------------------------------------------- ???????tx.commit(); ???????session.close(); ???????????} ???????????@Test ???//投影查询 ???//查询对象某一个属性 ???public void fun6(){ ???????Session session = HibernateUtils.openSession(); ???????Transaction tx = session.beginTransaction(); ???????//---------------------------------------------------- ???????String hql1 = " select cust_name from ?domain.Customer ?"; ???????String hql2 = " select cust_name,cust_id from ?domain.Customer ?"; ???????String hql3 = " select new Customer(cust_id,cust_name) from ?domain.Customer ?"; ???????//如果实体类有相应构造方法，也可以执行 ???????????????Query query = session.createQuery(hql2); ???????????????List list = query.list(); ???????????????System.out.println(list); ???????????????//---------------------------------------------------- ???????tx.commit(); ???????session.close(); ???????????}}多表查询：
再创建一个实体类：
package domain;//联系人实体public class LinkMan { ???private Long lkm_id; ???private Character lkm_gender; ???private String lkm_name; ???private String lkm_phone; ???private String lkm_email; ???private String lkm_qq; ???private String lkm_mobile; ???private String lkm_memo; ???private String lkm_position; ???// 表达多对一关系 ???private Customer customer; ???public Customer getCustomer() { ???????return customer; ???} ???public void setCustomer(Customer customer) { ???????this.customer = customer; ???} ???public Long getLkm_id() { ???????return lkm_id; ???} ???public void setLkm_id(Long lkm_id) { ???????this.lkm_id = lkm_id; ???} ???public Character getLkm_gender() { ???????return lkm_gender; ???} ???public void setLkm_gender(Character lkm_gender) { ???????this.lkm_gender = lkm_gender; ???} ???public String getLkm_name() { ???????return lkm_name; ???} ???public void setLkm_name(String lkm_name) { ???????this.lkm_name = lkm_name; ???} ???public String getLkm_phone() { ???????return lkm_phone; ???} ???public void setLkm_phone(String lkm_phone) { ???????this.lkm_phone = lkm_phone; ???} ???public String getLkm_email() { ???????return lkm_email; ???} ???public void setLkm_email(String lkm_email) { ???????this.lkm_email = lkm_email; ???} ???public String getLkm_qq() { ???????return lkm_qq; ???} ???public void setLkm_qq(String lkm_qq) { ???????this.lkm_qq = lkm_qq; ???} ???public String getLkm_mobile() { ???????return lkm_mobile; ???} ???public void setLkm_mobile(String lkm_mobile) { ???????this.lkm_mobile = lkm_mobile; ???} ???public String getLkm_memo() { ???????return lkm_memo; ???} ???public void setLkm_memo(String lkm_memo) { ???????this.lkm_memo = lkm_memo; ???} ???public String getLkm_position() { ???????return lkm_position; ???} ???public void setLkm_position(String lkm_position) { ???????this.lkm_position = lkm_position; ???}}测试类：
package hql;import java.util.Arrays;import java.util.List;import org.hibernate.Query;import org.hibernate.Session;import org.hibernate.Transaction;import org.junit.Test;import domain.Customer;import utils.HibernateUtils;//学习HQL语法(不常用) - 多表查询语法public class Demo2 { ???//原生SQL中： ???// 交叉连接-笛卡尔积(避免)// ???????select * from A,B ????// 内连接// ???????|-隐式内连接// ???????????select * from A,B ?where b.aid = a.id// ???????|-显式内连接// ???????????select * from A inner join B on b.aid = a.id ???// 外连接// ???????|- 左外// ???????????select * from A left [outer] join B on b.aid = a.id// ???????|- 右外// ???????????select * from A right [outer] join B on b.aid = a.id//---------------------------------------------------------------------//HQL的多表查询 ???????//内连接(迫切) ???????//外连接// ???????????|-左外(迫切)// ???????????|-右外(迫切) ???????@Test ???//HQL 内连接 => 将连接的两端对象分别返回.放到数组中. ???public void fun1(){ ???????Session session = HibernateUtils.openSession(); ???????Transaction tx = session.beginTransaction(); ???????//---------------------------------------------------- ???????String hql = " from Customer c inner join c.linkMens "; ???????//c相当于别名 ???????Query query = session.createQuery(hql); ???????????????List<Object[]> list = query.list(); ???????????????for(Object[] arr : list){ ???????????System.out.println(Arrays.toString(arr)); ???????} ???????//---------------------------------------------------- ???????tx.commit(); ???????session.close(); ???????????} ???????@Test ???//HQL 迫切内连接 => 帮我们进行封装.返回值就是一个对象 ???public void fun2(){ ???????Session session = HibernateUtils.openSession(); ???????Transaction tx = session.beginTransaction(); ???????//---------------------------------------------------- ???????String hql = " from Customer c inner join fetch c.linkMens "; ???????????????Query query = session.createQuery(hql); ???????????????List<Customer> list = query.list(); ???????????????System.out.println(list); ???????//---------------------------------------------------- ???????tx.commit(); ???????session.close(); ???????????} ???????@Test ???//HQL 左外连接 => 将连接的两端对象分别返回.放到数组中. ???public void fun3(){ ???????Session session = HibernateUtils.openSession(); ???????Transaction tx = session.beginTransaction(); ???????//---------------------------------------------------- ???????String hql = " from Customer c left join c.linkMens "; ???????????????Query query = session.createQuery(hql); ???????????????List<Object[]> list = query.list(); ???????????????for(Object[] arr : list){ ???????????System.out.println(Arrays.toString(arr)); ???????} ???????//---------------------------------------------------- ???????tx.commit(); ???????session.close(); ???????????} ???@Test ???//HQL 右外连接 => 将连接的两端对象分别返回.放到数组中. ???public void fun4(){ ???????Session session = HibernateUtils.openSession(); ???????Transaction tx = session.beginTransaction(); ???????//---------------------------------------------------- ???????String hql = " from Customer c right join c.linkMens "; ???????????????Query query = session.createQuery(hql); ???????????????List<Object[]> list = query.list(); ???????????????for(Object[] arr : list){ ???????????System.out.println(Arrays.toString(arr)); ???????} ???????//---------------------------------------------------- ???????tx.commit(); ???????session.close(); ???????????} ???}补上内连接与外连接区别：
hibernate框架学习笔记10：HQL查询详解
原文地址：https://www.cnblogs.com/xuyiqing/p/8454835.html