日期:2014-05-19  浏览次数:20745 次

hql 语句多表联合查询
现有需求如下:在数据库中有表一名为test1,属性有cid.cname,cpwd;表二名为test2,属性有did,dname,dpwd,并且两张表都在项目中又实体类映射,现在项目中有实体类映射test,属性为cid,cname,cpwd,did,dname,dpwd,我想写个hql语句,查询表test1与表test2,查询语句为:

  String sql="select CName,DName from Test1 test1,Test2 test2 where test1.Cid=test2.Did";

怎么才能把返回的list属性为test呢?不是test1,也不是test2,而是test呢?而这个test在数据库中不存在,可以嘛?

Java code

public List<Test> getAll()
    {
        String sql="select CName,DName from Test1 test1,Test2 test2 where test1.Cid=test2.Did";
        
        return (List<Test>)super.find(sql);
    }




------解决方案--------------------
1、将Test定义为一个Bean
2、提供默认构造函数和一个有参数的构造函数,这个有参数的构造函数的参数分别为cid,cname,cpwd,did,dname,dpwd
3、String sql="select new Test(cid,cname,cpwd,did,dname,dpwd
) from Test1 c,Test2 d where c.Cid=d.Did";

执行返回List<Test>
------解决方案--------------------
Java code



import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.List;
import java.util.Vector;

import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;

import y.model.Test;
import y.model.Test1;
import y.model.Test2;

import com.targ.track.financeManager.buildProjectAccount.domain.BuildProjectAccount;
import com.targ.track.financeManager.buildProjectAccount.domain.BuildProjectAccountDetail;
import com.targ.track.startAppManager.domain.StartApplication;



public class MyJunitTest {
    @org.junit.Test
    public void testDDL(){
        //插入数据
        HibernateTest.doInHibernateSession(new InHibernateSession(){
            @Override
            public Object doInHibernateSession(Session session) {
                Test1 test1 = new Test1();
                test1.setCAgo("CAgo");
                test1.setCName("CName");
                test1.setCPwd("CPwd");
                test1.setCSex("CSex");
                Test2 test2 = new Test2();
                test2.setDAddr("DAddr");
                test2.setDAge(123);
                test2.setDName("DName");
                test2.setDPwd("DPwd");
                test2.setDSex("DSex");
                session.save(test1);
                session.save(test2);
                return null;
            }
        });
        //查询
         List<Test> all = (List<Test>) HibernateTest.doInHibernateSession(new InHibernateSession(){
            public Object doInHibernateSession(Session session) {
                String sql="select new y.model.Test(c.CId,c.CName,d.DId,d.DName) from Test1 c,Test2 d where c.CId=d.DId";
                Query query = session.createQuery(sql);
                return query.list();
            }
        });
         for(Test test : all){
             System.out.println(test);
         }
        
    }
    public static class HibernateTest {
        public static Object doInHibernateSession(InHibernateSession doInHibernateSession){
            Session session = HibernateSessionFactory.getSession();
            Transaction transaction = session.beginTransaction();
            try{
                Object object =  doInHibernateSession.doInHibernateSession(session);
                transaction.commit();
                return object;
            }catch(RuntimeException e){
                try{
                    System.err.println("rollback");
                    transaction.rollback();
                }catch(RuntimeException ex){
                    System.err.println("回滚失败!&q