hibernate单表查询总结（下）
本博客接着hibernate单表查询总结（上）继续就Hibernate的单表查询进行总结
一、分页查询
public void testQuerySingleTable_HQL_PagingPuery() {
Session session = HbnUtils.getSession();
try {
session.beginTransaction();
String hql = "from Student";
int pageNo = 2;//当前页码
int pageSize = 3;//每页记录数
int firstResult =(pageNo - 1) * pageSize;//起始处
List<Student> list = session.createQuery(hql)
.setFirstResult(firstResult)
.setMaxResults(pageSize)
.list();
for (Student stu : list) {
System.out.println(stu);
}
session.getTransaction().commit();
} catch (Exception e) {
e.printStackTrace();
session.getTransaction().rollback();
}
}二、模糊查询
public void testQuerySingleTable_HQL_Vague() {
Session session = HbnUtils.getSession();
try {
session.beginTransaction();
String hql = "from Student where name like:name";
List<Student> list = session.createQuery(hql)
.setString("name", "%张%")
.list();
for (Student stu : list) {
System.out.println(stu);
}
session.getTransaction().commit();
} catch (Exception e) {
e.printStackTrace();
session.getTransaction().rollback();
}
}三、聚合函数查询
public void testQuerySingleTable_HQL_AggregateFunction() {
Session session = HbnUtils.getSession();
try {
session.beginTransaction();
String hql = "select count(id) from Student";
Long count = (Long) session.createQuery(hql).uniqueResult();
System.out.println("一共有："+count+"条数据");
session.getTransaction().commit();
} catch (Exception e) {
e.printStackTrace();
session.getTransaction().rollback();
}
}四、映射查询
（只取某几个字段）
public void testQuerySingleTable_HQL_Mapping() {
Session session = HbnUtils.getSession();
try {
session.beginTransaction();
String hql = "select new Student(name,age) from Student";
// 执行操作
List<Student> list = session.createQuery(hql)
.list();
for (Student stu : list) {
System.out.println(stu);
}
session.getTransaction().commit();
} catch (Exception e) {
e.printStackTrace();
session.getTransaction().rollback();
}
}五、分组查询
public void testQuerySingleTable_HQL_Group() {
Session session = HbnUtils.getSession();
try {
session.beginTransaction();
//查询有几个年龄段
String hql = "select age from Student gruoup by age";
// 执行操作
List<Integer> list = session.createQuery(hql).list();
// 执行操作
for (Integer age : list) {
System.out.println(age);
}
session.getTransaction().commit();
} catch (Exception e) {
e.printStackTrace();
session.getTransaction().rollback();
}
}六、命名查询
命名查询是将HQL语句配置到xml文件中，从而提高代码的可维护性，HQL语句可以配置到当前应用的任一xxx.hbm.xml文件中 
具体位置是在class标签后面 
public void testQuerySingleTable_HQL_NamedQuery() {
Session session = HbnUtils.getSession();
try {
session.beginTransaction();
//getNamedQuery("selectById")参数为配置文件里写的名字
Student stu = (Student) session.getNamedQuery("selectById").setInteger("id", 3).uniqueResult();
System.out.println(stu);
session.getTransaction().commit();
} catch (Exception e) {
e.printStackTrace();
session.getTransaction().rollback();
}
}七、关于单表查询的效率问题
在Query接口的List方法和Iterate方法总结一文中有详细讲述
