HQL(Hibernate Query Language)查询：
1、查询所有学生信息：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="from pers.zhb.domain.Student";
Query query= session.createQuery(hql);
List<Student>list=query.list();
System.out.println(list);
transaction.commit();
session.close();//游离状态
}
简化写法：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="from Student";
Query query= session.createQuery(hql);
List<Student> list=query.list();
System.out.println(list);
transaction.commit();
session.close();//游离状态
}
查询所有表的数据：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="from java.lang.Object";
Query query= session.createQuery(hql);
List<Object> list=query.list();
System.out.println(list);
transaction.commit();
session.close();//游离状态
}
2、条件查询（查询所有的女学生的信息）：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="from pers.zhb.domain.Student where sex='女'";
Query query= session.createQuery(hql);
List<Student>list=query.list();
System.out.println(list);
transaction.commit();
session.close();//游离状态
}
3、问号占位符的使用：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="from pers.zhb.domain.Student where studentno=?";
Query query= session.createQuery(hql);
query.setInteger(0,937221524);
Student student= (Student) query.uniqueResult();//获取唯一值
System.out.println(student);
transaction.commit();
session.close();
}
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="from pers.zhb.domain.Student where sex=?";
Query query= session.createQuery(hql);
//query.setFetchSize(0,"女");
query.setParameter(0,"女");//通用
List<Student> list=query.getResultList();
System.out.println(list);
transaction.commit();
session.close();
}
4、命名占位符：
省去了用数字指明属性位置的麻烦，直接用属性名代替。
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="from pers.zhb.domain.Student where sex=:sex";
Query query= session.createQuery(hql);
query.setParameter("sex","女");//通用
List<Student> list=query.getResultList();
System.out.println(list);
transaction.commit();
session.close();
}
5、分页查询：
需要指明从哪开始，要取几条数据：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="from pers.zhb.domain.Student where sex=:sex";
Query query= session.createQuery(hql);
query.setFirstResult(0);//从0开始
query.setMaxResults(2);//抓取两条数据
query.setParameter("sex","女");//通用
List<Student> list=query.getResultList();
System.out.println(list);
transaction.commit();
session.close();
}
6、排序查询：
（1）按学号升序排列：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="from pers.zhb.domain.Student order by studentno asc";
Query query= session.createQuery(hql);
List<Student> list=query.list();
System.out.println(list);
transaction.commit();
session.close();//游离状态
}
（2）分数降序：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="from pers.zhb.domain.Student order by point desc ";
Query query= session.createQuery(hql);
List<Student> list=query.list();
System.out.println(list);
transaction.commit();
session.close();//游离状态
}
7、统计查询：
（1）count：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="select count(*) from pers.zhb.domain.Student";
Query query= session.createQuery(hql);
Number number= (Number) query.uniqueResult();
System.out.println(number);
transaction.commit();
session.close();//游离状态
}
（2）sum求所有学生的分数和：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="select sum(point) from pers.zhb.domain.Student";
Query query= session.createQuery(hql);
Number number= (Number) query.uniqueResult();
System.out.println(number);
transaction.commit();
session.close();//游离状态
}
（3）avg求平均分：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="select avg(point) from pers.zhb.domain.Student";
Query query= session.createQuery(hql);
Number number= (Number) query.uniqueResult();
System.out.println(number);
transaction.commit();
session.close();//游离状态
}
（4）min求最低分：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="select min(point) from pers.zhb.domain.Student";
Query query= session.createQuery(hql);
Number number= (Number) query.uniqueResult();
System.out.println(number);
transaction.commit();
session.close();//游离状态
}
8、投影：
（1）查询每个学生的名字：
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="select sname from pers.zhb.domain.Student";
Query query= session.createQuery(hql);
List list= query.list();
System.out.println(list);
transaction.commit();
session.close();//游离状态
}
（2）查询学生的姓名和学号：
创建构造方法（用于存储姓名和学号）：
public Student(Integer studentno,String sname){
super();
this.studentno=studentno;
this.sname=sname;
}
public static void testSel() {
Session session = HibernateUtils.openSession();
Transaction transaction = session.beginTransaction();
String hql="select new Student(studentno,sname) from pers.zhb.domain.Student";
Query query= session.createQuery(hql);
List<Object[]> list= query.list();
System.out.println(list);
transaction.commit();
session.close();//游离状态
}
