HQL基本的举例

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java 代码

/*
* 简单的查询一个表，返回List
*/
public void testHQL1(){
Session session = factory.openSession();
String hql = "from User";
Query query = session.createQuery(hql);
List users = query.list();
for(User user : users){
System.out.println(user.getName());
System.out.println("---------------");
}
session.close();
}
/*
*
* 加了一些限制的条件查询，查询得到一个List
* 这里跟 sql 语句很像，很好！
*/
public void testHQL2(){
Session session = factory.openSession();
String hql = "from User where name='linweihan' and addr ='beijing'";
Query query = session.createQuery(hql);
List users = query.list();
for(User user : users){
System.out.println(user.getName());
System.out.println("---------------");
}
session.close();
}
/*
* 排序，使用order by和sql 非常像很好
*/
public void testHQL3(){
Session session = factory.openSession();
String hql = "from User order by age desc";
Query query = session.createQuery(hql);
List users = query.list();
for(User user : users){
System.out.println(user.getAge());
System.out.println(user.getName());
System.out.println("---------------");
}
session.close();
}
/*
* 分组，使用group by
*/
public void testHQL4(){
Session session = factory.openSession();
String hql = "from User group by addr";
Query query = session.createQuery(hql);
List users = query.list();
for(User user : users){
System.out.println(user.getAge());
System.out.println(user.getName());
System.out.println(user.getAddr());
System.out.println("---------------");
}
session.close();
}
/*
* 使用函数
* 这里使用avg(),平均数
* 跟sql很像啊
*/
public void testHQL5(){
Session session = factory.openSession();
String hql = "select avg(age) from User";
//这里返回的List是float类型的
Query query = session.createQuery(hql);
List avg_ages = query.list();
for(Float avg_age : avg_ages){
System.out.println(avg_age);
}
session.close();
}
/*
* 分组和函数相结合
*
*/
public void testHQL6(){
Session session = factory.openSession();
String hql = "select avg(age) from User group by addr";
//这里返回的List是float类型的
Query query = session.createQuery(hql);
List avg_ages = query.list();
for(Float avg_age : avg_ages){
System.out.println(avg_age);
}
session.close();
}
/*
* 分组和函数相结合，查询平均年龄和地址
* 所以返回的类型应该是Object
*
*/
public void testHQL7(){
Session session = factory.openSession();
String hql = "select avg(age),addr from User group by addr";
Query query = session.createQuery(hql);
List avg_ages = query.list();
for(Object[] avg_age : avg_ages){
System.out.println(avg_age[1]+"----"+avg_age[0]);
}
session.close();
}
/*
* 支持select 这种通用的查询
*/
public void testHQL8(){
Session session = factory.openSession();
String hql = "select name,age from User";
Query query = session.createQuery(hql);
List infos = query.list();
for(Object[] info : infos){
System.out.println(info[0]+"----"+info[1]);
}
session.close();
}
/*
* 使用update
* Hibernate3也支持update和delete
* 在Hibernate2中不支持
*/
public void testHQL9(){
Session session = factory.openSession();
String hql = "update User set age = 100 where name = 'linweihan'";
Query query = session.createQuery(hql);
//需要用executeUpdate方法
query.executeUpdate();
//需要事务的提交才能影响数据库
session.beginTransaction().commit();
session.close();
}
/*
* 使用delete
*/
public void testHQL10(){
Session session = factory.openSession();
String hql = "delete User where name = 'linweihan'";
Query query = session.createQuery(hql);
//需要用executeUpdate方法
query.executeUpdate();
//需要事务的提交才能影响数据库
session.beginTransaction().commit();
session.close();
}
/*
* 在JDBC支持动态的参数
* 在hibernate中也支持
*/
public void testHQL11(){
Session session = factory.openSession();
String hql = "from User where addr=? and age=?";
Query query = session.createQuery(hql);
query.setString(0, "fujian");
query.setInteger(1, 22);
List users = query.list();
for(User user : users){
System.out.println(user.getName());
System.out.println("---------------");
}
//session.close();
}
/*
* HQL中支持这么一种的动态帮定可以起别名
*/
public void testHQL12(){
Session session = factory.openSession();
String hql = "from User where addr=:address and age=:age";
Query query = session.createQuery(hql);
query.setString("address", "fujian");
query.setInteger("age", 22);
List users = query.list();
for(User user : users){
System.out.println(user.getName());
System.out.println("---------------");
}
session.close();
}
/*
* 另外Hibernate允许我们把 sql语句配置到文件中
* 因为写到程序中需要编译的，而写到配置文件中是不需要编译的
*/