-
// HQL: Hibernate Query Language.
// 特点：// >> 1，与SQL相似，SQL中的语法基本上都可以直接使用。// >> 2，SQL查询的是表和表中的列；HQL查询的是对象与对象中的属性。// >> 3，HQL的关键字不区分大小写，类名与属性名是区分大小写的。// >> 4，SELECT可以省略. // 1，简单的查询，Employee为实体名而不是数据库中的表名(面向对象特性)hql = "FROM Employee";hql = "FROM Employee AS e"; // 使用别名hql = "FROM Employee e"; // 使用别名，as关键字可省略// 2，带上过滤条件的（可以使用别名）：Where
hql = "FROM Employee WHERE id<10";hql = "FROM Employee e WHERE e.id<10";hql = "FROM Employee e WHERE e.id<10 AND e.id>5";// 3，带上排序条件的：Order By
hql = "FROM Employee e WHERE e.id<10 ORDER BY e.name";hql = "FROM Employee e WHERE e.id<10 ORDER BY e.name DESC";hql = "FROM Employee e WHERE e.id<10 ORDER BY e.name DESC, id ASC";// 4，指定select子句（不可以使用select *）
hql = "SELECT e FROM Employee e"; // 相当于"FROM Employee e"hql = "SELECT e.name FROM Employee e"; // 只查询一个列，返回的集合的元素类型就是这个属性的类型hql = "SELECT e.id,e.name FROM Employee e"; // 查询多个列，返回的集合的元素类型是Object数组hql = "SELECT new Employee(e.id,e.name) FROM Employee e"; // 可以使用new语法，指定把查询出的部分属性封装到对象中// 5，执行查询，获得结果（list、uniqueResult、分页 ）
Query query = session.createQuery("FROM Employee e WHERE id<3");query.setFirstResult(0);query.setMaxResults(10); // 等同于 limit 0,10//两种查询结果list、uniqueResult// List list = query.list(); // 查询的结果是一个List集合// Employee employee = (Employee) query.uniqueResult();// 查询的结果是唯一的一个结果，当结果有多个，就会抛异常// 6，方法链
List list = session.createQuery(// "FROM Employee e")// .setFirstResult(0)// .setMaxResults(10)// .list();// 7，聚集函数：count(), max(), min(), avg(), sum()
hql = "SELECT COUNT(*) FROM Employee"; // 返回的结果是Long型的hql = "SELECT min(id) FROM Employee"; // 返回的结果是id属性的类型//8，分组: Group By ... Having
hql = "SELECT e.name,COUNT(e.id) FROM Employee e GROUP BY e.name";hql = "SELECT e.name,COUNT(e.id) FROM Employee e GROUP BY e.name HAVING count(e.id)>1";hql = "SELECT e.name,COUNT(e.id) FROM Employee e WHERE id<9 GROUP BY e.name HAVING count(e.id)>1";hql = "SELECT e.name,COUNT(e.id) " + // "FROM Employee e " + // "WHERE id<9 " + // "GROUP BY e.name " + // "HAVING count(e.id)>1 " + // "ORDER BY count(e.id) ASC";hql = "SELECT e.name,COUNT(e.id) AS c " + // "FROM Employee e " + // "WHERE id<9 " + // "GROUP BY e.name " + // "HAVING count(e.id)>1 " + // 在having子句中不能使用列别名 "ORDER BY c ASC"; // 在orderby子句中可以使用列别名// 9，连接查询 / HQL是面向对象的查询
//>> 内连接（inner关键字可以省略） hql = "SELECT e.id,e.name,d.name FROM Employee e JOIN e.department d"; hql = "SELECT e.id,e.name,d.name FROM Employee e INNER JOIN e.department d"; //>> 左外连接（outer关键字可以省略） hql = "SELECT e.id,e.name,d.name FROM Employee e LEFT OUTER JOIN e.department d"; //>> 右外连接（outer关键字可以省略） hql = "SELECT e.id,e.name,d.name FROM Employee e RIGHT JOIN e.department d"; //可以使用更方便的方法 hql = "SELECT e.id,e.name,e.department.name FROM Employee e";// 10，查询时使用参数
// >> 方式一：使用'?'占位 hql = "FROM Employee e WHERE id BETWEEN ? AND ?"; List list2 = session.createQuery(hql)// .setParameter(0, 5)// 设置参数，第1个参数的索引为0。 .setParameter(1, 15)// .list();// >> 方式二：使用变量名
hql = "FROM Employee e WHERE id BETWEEN :idMin AND :idMax"; List list3 = session.createQuery(hql)// .setParameter("idMax", 15)// .setParameter("idMin", 5)// .list();// 当参数是集合时，一定要使用setParameterList()设置参数值
hql = "FROM Employee e WHERE id IN (:ids)"; List list4 = session.createQuery(hql)// .setParameterList("ids", new Object[] { 1, 2, 3, 5, 8, 100 })// .list();// 11，update与delete，不会通知Session缓存
// >> Updateint result = session.createQuery(// "UPDATE Employee e SET e.name=? WHERE id>15")// .setParameter(0, "无名氏")// .executeUpdate(); // 返回int型的结果，表示影响了多少行。// >> Deleteint result1 = session.createQuery(// "DELETE FROM Employee e WHERE id>15")// .executeUpdate(); // 返回int型的结果，表示影响了多少行。 -
1. 查询整个映射对象所有字段
//直接from查询出来的是一个映射对象，即：查询整个映射对象所有字段String hql ="from Users";Query query = session.createQuery(hql);List<Users> users = query.list();for(Users user : users){System.out.println(user.getName() +" : "+ user.getPasswd() +" : "+ user.getId());}输出结果为：name1 : password1 :1name2 : password2 :2name3 : password3 :32.查询字段
//查询其中几个字段String hql =" select name,passwd from Users";Query query = session.createQuery(hql);//默认查询出来的list里存放的是一个Object数组List<Object[]> list = query.list();for(Object[] object : list){String name = (String)object[0];String passwd = (String)object[1];System.out.println(name +" : "+ passwd);}输出结果为：name1 : password1name2 : password2name3 : password33.修改默认查询结果(query.list())不以Object[]数组形式返回，以List形式返回
//查询其中几个字段,添加new list(),注意list里的l是小写的。也不需要导入包，这样通过query.list()出来的list里存放的不再是默认的Object数组了，而是List集合了String hql =" select new list(name,passwd) from Users";Query query = session.createQuery(hql);//默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是List集合了List<List> list = query.list();for(List user : list){String name = (String)user.get(0);String passwd = (String)user.get(1);System.out.println(name +" : "+ passwd);}/**输出结果为：name1 : password1name2 : password2name3 : password3*/4.修改默认查询结果(query.list())不以Object[]数组形式返回，以Map形式返回
//查询其中几个字段,添加new map(),注意map里的m是小写的。也不需要导入包，这样通过query.list()出来的list里存放的不再是默认的Object数组了，而是map集合了String hql =" select new map(name,passwd) from Users";Query query = session.createQuery(hql);//默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是Map集合了List<Map> list = query.list();for(Map user : list){//一条记录里所有的字段值都是map里的一个元素,key是字符串0,1,2,3....，value是字段值//如果将hql改为：String hql = " select new map(name as username,passwd as password) from Users";,那么key将不是字符串0,1,2...了，而是"username","password"了String name = (String)user.get("0");//get("0");是get(key),注意:0,1,2...是字符串，而不是整形String passwd = (String)user.get("1");System.out.println(name +" : "+ passwd);}/**输出结果为：name1 : password1name2 : password2name3 : password3*/5.修改默认查询结果(query.list())不以Object[]数组形式返回，以自定义类型返回
6.条件查询
//条件查询，参数索引值从0开始，索引位置。通过setString,setParameter设置参数String hql ="from Users where name=? and passwd=?";Query query = session.createQuery(hql);//第1种方式// query.setString(0, "name1");// query.setString(1, "password1");//第2种方式query.setParameter(0,"name1",Hibernate.STRING);query.setParameter(1,"password1",Hibernate.STRING);List<Users> list = query.list();for(Users users : list){System.out.println(users.getId());}//条件查询，自定义索引名(参数名):username,:password.通过setString,setParameter设置参数String hql ="from Users where name=:username and passwd=:password";Query query = session.createQuery(hql);//第1种方式// query.setString("username", "name1");// query.setString("password", "password1");//第2种方式,第3个参数确定类型query.setParameter("username","name1",Hibernate.STRING);query.setParameter("password","password1",Hibernate.STRING);List<Users> list = query.list();for(Users users : list){System.out.println(users.getId());}//条件查询,通过setProperties设置参数String hql ="from Users where name=:username and passwd=:password";Query query = session.createQuery(hql);//MyUser类的2个属性必须和:username和:password对应MyUser myUser =newMyUser("name1","password1");query.setProperties(myUser);List<Users> list = query.list();for(Users users : list){System.out.println(users.getId());}7.update 数据
执行SQL语句（为什么要用SQL语句，我想是为了执行某些复杂的SQL语句吧）
String sql="update Table set field = 'test'"Session session = HibernateSessionFactory.getSession();session.createSQLQuery(sql).executeUpdate();ts.commit();执行HQL语句
String hql="update Table set field = 'test'"Session session = HiberanteSessionFactory.getSession();Transaction ts = session.beginTransaction();Query query = session.createQuery(hql);query.executeUpdate();ts.commit();