Hibernate 的HQL,QBC 查询语言

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

1.实体查询

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

2.有条件的实体查询

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<Employee> 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<Employee> list= query.list();
//...
}
public void testQueryDeptByGt(){
String hql="from Dept model where model.createDate> '2012-03-10'";
Query query=session.createQuery(hql);
List<Employee> list= query.list();
}

3.HQL 中的各种运算符

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

3.更新删除

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();
}

4.属性查询

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

5.使用函数

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

6.分组与排序

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

7.查询单个对象

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);
}

8.绑定参数
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
odel.deptName=:deptName and model.createDate=:createDate";
Query query=session.createQuery(hql);
query.setString("deptName","test");
query.setString("ceateDate","2000-02-10");
List<Dept> 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<Dept> 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<Employee> 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<Dept> 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<Dept> deptList=query.list();
for(){
}
//..
}

10. 联合查询
inner join

public void testQueryInnerJoin(){
String hql="from Dept as model inner join model1.employees as model2";
Query query=session.createQuery(hql);
List<Object[]> 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<Object[]> 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<Object[]> 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());
}
}

11.子查询

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

12 Criteria 查询
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<Dept> 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<Dept> deptList=criteria.list();
for(){}
//..
}

SQL语法查询机制

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<value
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<field
Expression.leProperty	用于比较两个属性之间的值,对应field<=field

Hibernate3中采用Restrictions类代替Expression

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

Criteria中限定返回的行数

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

Criteria排序

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

巴特西

Hibernate 的HQL,QBC 查询语言

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