Hibernate HQL的子查询

子查询是SQL中很重要的功能，他可以在SQL中利用另外一条SQL的查询结果，HQL同样支持此机制

如果子查询返回都条记录，可以用以下关键字进行量化

all: 表示所有记
any:表示所有记录中的任意1条
some:与any用法一样
in:与=any等价
exist: 表示子查询至少要返回一条记录

数据库结构：

 

create table testStu (id varchar(32),name varchar(32),age int,team_id varchar(32));

insert into teststu values("1","tom1",11,"1");
insert into teststu values("2","tom2",12,"2");
insert into teststu values("3","tom3",13,"1");
insert into teststu values("4","tom4",14,"2");
insert into teststu values("5","tom5",15,"1");
insert into teststu values("6","tom6",16,"2");
insert into teststu values("7","tom7",17,"1");
insert into teststu values("8","tom8",18,"2");
insert into teststu values("9","tom9",19,"1");
insert into teststu values("10","tom10",20,"2");


create table testteam (id varchar(32) primary key,name varchar(32));

insert into testteam values("1","team1");
insert into testteam values("2","team2");

 

POJO:

 

package Search.filter;

public class TestStu ...{
    private String id; //标识id
    private String name; //学生姓名
    private int age; //岁数
    private TestTeam team;
  

     public int getAge() ...{
        return age;
    }

    public String getName() ...{
        return name;
    }



    public void setId(String id) ...{
        this.id = id;
    }

    public void setAge(int age) ...{
        this.age = age;
    }

    public void setName(String stuName) ...{
        this.name = stuName;
    }



    public String getId() ...{
        return id;
    }

    public TestStu() ...{ //无参的构造函数
    }

    public TestTeam getTeam() ...{
        return team;
    }

    public void setTeam(TestTeam team) ...{
        this.team = team;
    }

}


package Search.filter;

import java.util.Set;

public class TestTeam ...{
   private String id;
   private String name;
   private Set students;
public String getId() ...{
    return id;
}
public void setId(String id) ...{
    this.id = id;
}
public String getName() ...{
    return name;
}
public void setName(String name) ...{
    this.name = name;
}
public Set getStudents() ...{
    return students;
}
public void setStudents(Set students) ...{
    this.students = students;
}
}

 

Hibernate.cfg.xml

 

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>

<session-factory>
    <property name="connection.username">root</property>
    <property name="connection.url">
        jdbc:mysql://localhost:3306/schoolproject?characterEncoding=gb2312&amp;useUnicode=true
    </property>
    <property name="dialect">
        org.hibernate.dialect.MySQLDialect
    </property>
    <property name="myeclipse.connection.profile">mysql</property>
    <property name="connection.password">1234</property>
    <property name="connection.driver_class">
        com.mysql.jdbc.Driver
    </property>
    <property name="hibernate.dialect">
        org.hibernate.dialect.MySQLDialect
    </property>
    <property name="hibernate.show_sql">true</property>
    <property name="current_session_context_class">thread</property>
    <mapping resource="Search/sub/TestStu.hbm.xml" />
    <mapping resource="Search/sub/TestTeam.hbm.xml" />

</session-factory>

</hibernate-configuration>

 

TestStu.hbm.xml

 

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping package="Search.fetch" >
   
    <class name="Search.sub.TestStu" table="teststu" lazy="true">
       <id name="id" column="id" unsaved-value="null">
         <generator class="uuid.hex"></generator>
       </id>

       <property name="name" column="name"></property>
       <property name="age" column="age"></property>
       <many-to-one name="team" column="team_id">
       </many-to-one>
      </class>
</hibernate-mapping>

TestTeam.hbm.xml

 

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping>
<class name="Search.sub.TestTeam" table="testteam" lazy="true">
    <id name="id" column="id" unsaved-value="null">
        <generator class="uuid.hex"></generator>
    </id>
    <property name="name" column="name" type="string"></property>
    <set name="students" inverse="true" lazy="true" fetch="select">
      <key column="team_id"></key>
      <one-to-many class="Search.sub.TestStu"/>

    </set>
 </class>   

</hibernate-mapping>

 

测试代码：

 

package Search.sub;

import java.io.File;
import java.util.Iterator;
import java.util.List;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

public class Test ...{


    public static void main(String[] args)...{
        String filePath=System.getProperty("user.dir")+File.separator+"src/Search/sub"+File.separator+"hibernate.cfg.xml";
        File file=new File(filePath);
        SessionFactory sessionFactory=new Configuration().configure(file).buildSessionFactory();
        Session session=sessionFactory.openSession();
        Transaction t=(Transaction)session.beginTransaction();
        
        //查询所有学生年龄都大于11岁的班级对象（结果应为team2）
        //team1学生年龄是11,13,15,17,19
        //team2学生年龄是12，14，16，17，20
        /**//*
         * 使用SQL
         * select t1.name
           from testteam t1
           where 11<all(SELECT s.age from teststu s where s.team_id=t1.id);
         */
        Query query=session.createQuery("from TestTeam t where 11<all(select s.age from t.students s)");
        //注意：不能将11<all 写成all>11以违反Mysql规则
        List teamList=query.list();
        for (Iterator iterator = teamList.iterator(); iterator.hasNext();) ...{
            TestTeam object = (TestTeam) iterator.next();
            System.out.println(object.getName());
        }
        
        //查询有一个学生的年龄为15岁的team对象(结果应为team1)
        /**//*
         * 使用SQL
         * select t1.name
           from testteam t1
           where 15=any(SELECT s.age from teststu s where s.team_id=t1.id);
         */
        Query query1=session.createQuery("from TestTeam t where 15=any(select s.age from t.students s)");
        List teamList1=query1.list();
        for (Iterator iterator = teamList1.iterator(); iterator.hasNext();) ...{
            TestTeam object1 = (TestTeam) iterator.next();
            System.out.println(object1.getName());
        }
        t.commit();

    }

}

 

运行结果：

Hibernate: select testteam0_.id as id1_, testteam0_.name as name1_ from testteam testteam0_ where 11<all (select students1_.age from teststu students1_ where testteam0_.id=students1_.team_id)
team2
Hibernate: select testteam0_.id as id1_, testteam0_.name as name1_ from testteam testteam0_ where 15=any (select students1_.age from teststu students1_ where testteam0_.id=students1_.team_id)
team1

 

HQL子查依赖底层数据库的子查询能力，所以，要根据所使用的数据库来决定是否是用你HQL子查询，为了更多的移植性，最好使用连接查询和分组查询代替子查询