Hibernate 的HQL,QBC 查询语言

1.HQL:(Hibernate Query Language) 是面向对象的查询语言

[b][size=large][color=red]1.实体查询[/color][/size][/b]

	public void testQueryAllDept(){
	String hql="from Employee";
        //hql="from com.sh.Entity";
	Query query=session.createQuery(hql);

	List list= query.list();

	//...
	}

[b][size=large][color=red]2.有条件的 实体查询[/color][/size][/b]

	public void testQueryAllDept(){
	String hql="from Deptas model where mode.deptName='人事部' ";
        //hql="from com.sh.Entity";
	Query query=session.createQuery(hql);

	List list= query.list();

	//...
	}
	public void testQueryAllDept(){
	String hql="from Deptas model where mode.deptName like '%部%' ";
        //hql="from com.sh.Entity";
	Query query=session.createQuery(hql);

	List list= query.list();

	//...
	}

  public void testQueryDeptByGt(){

  String hql="from Dept model where model.createDate> '2012-03-10'";
  Query query=session.createQuery(hql);
  List list= query.list();
  }

3.HQL 中的各种运算符
[table]
|运算符类型|HQL运算符|含义
|比较运算|=| 等于
||<>|不等于
||>|大于
||>=|大于等于
||<=|小于等于
||<|小于
||is null|为空
||is not null|不为空
|范围运算|in|等于列表中的某一值
||not in| 不等于列表中的任意一个值
||between p1 and p2 |大于等于值1 且 小于等于值2
||not between p1 and p2|小于值1 或者 大于 值2
|字符串模式匹配|like|字符串模式匹配
|逻辑运算|and | 与
||or|或
||not|非
[/table]

[b][size=large][color=red]3.更新 删除[/color][/size][/b]

public void testModifyDate(){
		Transaction tr=session.beginTransaction();
		Dept detp=(Dept)session.get(Detp.class,new Integer(6));
		detp.seteCreateDate("2000-03-10");
		tr.commit();

	}

// delete  删除
public void testDelDeptByHql(){
		Transaction tr=session.beginTransaction();
		String hql="delete Dept as model where model.deptId=6";
		Query query=session.createQuery(hql);
		query.executeUpdate();
		tr.commit();
	}

[b][size=large][color=red]4.属性查询[/color][/size][/b]

	public void testQueryDeptName(){
		String hql="select model.deptName from Dept as model";
		Query query=session.createQuery(hql);
		List deptNameList=query.list();
		//...
	}
        public void testQueryDeptName(){
		String hql="select model.deptName,model.createDate from Dept as model";
		Query query=session.createQuery(hql);
		List prsList=query.list();
                for(){
                }               
		//...
	}

    //采用对象进行 保存 查询的字段(要添加 对应字段的构造方法)
     public void testQueryDeptName(){
		String hql="select new Dapt(model.deptName,model.createDate) from Dept as model";
		Query query=session.createQuery(hql);
		List deptList=query.list();
                for(Dept d:deptList){

                   d.setDeptName("test");
                   session.saveOrUpdate(dept);
                }               
		//...
	}


    //如果采用对象 保存上面查询出来的对象  如果对其进行更新的操作 是不会成功的

	public void testSaveDept(){
		Transction  tr=session.beginTransactino();
		String hql="select new Dept(model.deptName,model.createDate) from Dept as model";
		Query query=session.createQuery();
		List deptList=query.list();
		for(Dept dept:deptList){
			System.out.println(dept.deptName);
			dept.setDetpName("test");
			session.saveOrUpdate(dept);
		}
		tr.commit();
       // 最后 根本就没有更新 而是 在数据库中 插入 新的记录
	}

[b][size=large][color=red]5.使用函数[/color][/size][/b]

public void testQuyeryFunction(){
		String hql="select count(*),min(model.createDate) from Dept as model";
		Query query=session.createQuery(hql);
		List paramsList=query.list();
		for(){

		}
		//...
	}

[b][size=large][color=red]6.分组 与 排序[/color][/size][/b]

//排序
public void testQueryOrderBy(){
		String hql="from Dept as mode order by   model.createDate,model.deptName desc";
		Query query=session.createQuery();
		List deptList=query.list();
		for(){}
		//

	}

//分组 并且 使用  having 筛选
public void testQueryGroupBy(){
		String hql="select count(model),model.deptName from Dept as model group by model.deptName having count(model)>1";
		Query query=session.createQuery();
		List list=query.list();
		//...
	}

[b][size=large][color=red]7.查询单个对象[/color][/size][/b]

public void testQueryUn(){
		String hql="select model.deptName from Dept as model where model.deptId=2";
		Query query=session.createQuery(hql);
		query.setMaxResults(1);
		String deptName=(String)query.uniqueResult();
		System.out.println(deptNamae);
	}

[b][size=large][color=red]8.绑定参数[/color][/size][/b]
释义:Hibernate中也采用了preparedStatement作为底层数据库的的访问方式,与之对应的SQL语句 可以重用preparedStatement对象, 首先会预编译,然后缓存起来,提高性能.

1.使用 ":"加参数名 绑定参数

	public void  testQueryByParamsName(){
            //使用  ":参数名" 来传递参数
		String hql="from Dept as model where 
model.deptName=:deptName and model.createDate=:createDate";

		Query query=session.createQuery(hql);
		query.setString("deptName","test");
		query.setString("ceateDate","2000-02-10");
		List deptList=query.list();
		for(){}

		//...

	}

2.使用 "?" 按照位置来绑定参数

	public void testQueryByParamsID(){
		String hql="from Dept as model where model.deptName=? and model.createDate=?";
		Query query=session.createQuery(hql);
		query.setString(0,"test");
		query.setString(1,"2000-02-02");
		List list=query.list();
		for(){}
		//..
	}

3.采用setEntity() 将参数和一个持久化对象进行绑定

public void testQueryByDept(){
		Dept dept=(Dept)Session.get(Dept.clas,new Integer(2));
		String hql="select Employee  as model where model.dept=?"
		Query query=session.createQuery(hql);
		query.setEntity(0,dept);
		List empList=query.list();
		for(){}
		//..


	}

4.setParameter() 用于绑定任意类型的参数

public void testQueryBySetParams(){
		String hql="from Dept as model where model.deptName=?";
		Query query=session.createQuery(hql);
		query.setParameter(0,"test");
		List deptList=query.list();
		for(){}
		//..
	}

5.setProperties() 将一个参数名 于一个对象的属性值绑定

public void testQueryBySetPro(){
		Dept deptNew=new  Dept();
		deptNew.setDeptName("test");

		String hql="from Dept as model where model.deptName=:deptName";
		Query query=session.createQuery();
		query.setProperties(deptNew);
		List deptList=query.list();
		for(){

		}
		//..

	}

[b][size=large][color=red]10. 联合查询[/color][/size][/b]
inner join

public void testQueryInnerJoin(){
		String hql="from Dept as model inner join model1.employees as model2";
		Query query=session.createQuery(hql);
		List objList=query.list();
		for(Object[] obj:objList){
			Dept dept=(Dept)obj[0];
			Employee emp=(Employee)obj[1];
			System.out.println("xxxx");
		}
	}

left join

public void testQueryLeftJoin(){
		String hql="from Dept as model left join model1.employees as model2";
		Query query=session.createQuery(hql);
		List objList=query.list();
		for(Object[] obj:objList){
			Dept dept=(Dept)obj[0];
			Employee emp=(Employee)obj[1]; //有可能为空 所以需要判断
			if(mep!=null){
				System.out.println("xxxx");
			}else{
				System.out.println(null);
			}
			System.out.println(dept.getDeptName());
		}
	}

right join

	public void testQueryRightJoin(){
		String hql="from Dept as model right join model1.employees as model2";
		Query query=session.createQuery(hql);
		List objList=query.list();
		for(Object[] obj:objList){
			Dept dept=(Dept)obj[0];
			Employee emp=(Employee)obj[1]; //有可能为空 所以需要判断
			if(dept!=null){
				System.out.println(dept.getDeptName());
			}else{
				System.out.println(null);
			}
			System.out.println("dd"+emp.getEmployeeName());
		}
	}

[b][size=large][color=red]11.子查询[/color][/size][/b]

	public void testQueryChild(){
		String hql="from Dept as model where (select count(*) from model.employee) >2";
		Query query=session.createQuery(hql);
		List objList=query.list();
		for(){}
		//..
	}

[b][size=large][color=red]12 Criteria 查询[/color][/size][/b]
释义:通过面向对象的设计将数据查询条件封装在一个对象

//无条件
public void testQueryDept(){
		Criteria criteria=session.createCriteria(Dept.class);
		List deptList=criteria.list();
		for(){}
		//..
	}

//添加条件
public void testQueryDeptByName(){
		Criteria criteria=session.createCriteria(Dept.class);
		criteria.add(Expression.eq("deptName", "人事部"));
		List deptList=criteria.list();
		for(){}
		//..
	}

[b][size=large][color=red]SQL语法查询机制[/color][/size][/b]
[table]
|方法|描述
|Expression.eq|对应sql中的field =value
|Expression.gt|对应sql中的field>value
|Expression.ge|对应sql中的field>=value
|Expression.lt|对应sql中的field|Expression.le|对应sql中的field<=value
|Expression.between|对应sql中的between
|Expression.like|对应 like
|Expression.in|对应 in
|Expression.eqProperty|用于比较两个属性之间的值,对应的Sql条件中field=field
|Expression.gtProperty|用于比较两个属性之间的值,对Sqlfiled>field
|Expression.geProperty|用于比较两个属性之间的值,对应sql field>=field
|Expression.ltProperty|用于比较两个属性之间的值,对应field|Expression.leProperty|用于比较 两个属性之间的值,对应field<=field
[/table]


[b][size=large][color=red]Hibernate3中采用Restrictions类代替Expression[/color][/size][/b]

public void  testQueryDeptByNameRe(){
		Criteria  criteria=session.createCriteria(Dept.class);
		criteria.add(Restrictions.eq("deptName", "人事部"));
		List deptList=criteria.list();
		for(){}
		//..

	}

[b][size=large][color=red]Criteria中限定返回的行数[/color][/size][/b]

public void testQueryDept(){
		Criteria criteria=session.createCriteria(Dept.class);
		criteria.setFirstResult(2);
		criteria.setMaxResults(2);
		List deptList=criteria.list();
		for(){}
		//..
	}

[b][size=large][color=red]Criteria排序[/color][/size][/b]

public void testQueryDept(){
		Criteria criteria=session.createCriteria(Dept.class);
		criteria.addOrder(Order.asc("createDate"));
		List deptList=criteria.list();
		for(){}
		//..
	}