常用的Hql语句
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// 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
// >> Update
int 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。
// >> Delete
int 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 :
1
name2 : password2 :
2
name3 : password3 :
3
2.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 : password1
name2 : password2
name3 : password3
3.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 : password1
name2 : password2
name3 : 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 : password1
name2 : password2
name3 : 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 =
new
MyUser(
"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();