hql是非常有意识的被设计为完全面向对象的查询

基本规则:

1.hql语法类似于sql,但它后面跟的不是表名和字段名,而是类名和属性名

2.hql大小写不敏感.但是设计java类名,包名,属性名时大小写敏感.

public void test1(){ //重要
  Session session = HibUtil.getSession();
  Transaction tx =session.beginTransaction();
  Query query =session.createQuery("from Emp e");
  List<Emp> empList = query.list();
  for(Emp e:empList){
  System.out.println(e.getEname());
  }
  tx.commit();
  session.close();
}
public void test2(){ //单个对象 重要
  Session session = HibUtil.getSession();
  Transaction tx =session.beginTransaction();
  Query query =session.createQuery("select count(*) from Emp e");//集合函数查询
  Long n = (Long) query.uniqueResult();
  System.out.println(n);
  tx.commit();
  session.close();
}
public void test3(){ //单个对象 重要
  Session session = HibUtil.getSession();
  Transaction tx =session.beginTransaction();
  Query query =session.createQuery("from Emp e where e.empno=7369");
  Emp emp = (Emp) query.uniqueResult();
  System.out.println(emp.getEname());
  tx.commit();
  session.close();
}
public void test4(){ //Object[] 次重要
  Session session = HibUtil.getSession();
  Transaction tx =session.beginTransaction();
  Query query =session.createQuery("select e.empno,e.ename from Emp e ");
  List<Object[]> list =query.list();
  for(Object[] obj:list){
    System.out.println(obj[0]+"-->"+obj[1]);
  }
  tx.commit();
  session.close();
}
public void test5(){ //map 次重要
  Session session = HibUtil.getSession();
  Transaction tx =session.beginTransaction();
  Query query =session.createQuery("select new map(e.empno as empno,e.ename as ename) from Emp e ");
  List<Map<String,Object>> list =query.list();
  for(Map<String,Object> map:list){
    System.out.println(map.get("empno")+"-->"+map.get("ename"));
  }
  tx.commit();
  session.close();
}
public void test6(){ //对象 次重要
  Session session = HibUtil.getSession();
  Transaction tx =session.beginTransaction();
  Query query =session.createQuery("select new com.cdsxt.hib.vo.EmpVo(e.empno,e.ename) from Emp e ");//投影查询
  List<EmpVo> list =query.list();
  for(EmpVo emp:list){
    System.out.println(emp.getEmpno()+"-->"+emp.getEname());
  }
  tx.commit();
  session.close();
}
public void test7(){ //where条件 重要
  Session session = HibUtil.getSession();
  Transaction tx =session.beginTransaction();
  // Query query =session.createQuery("from Emp e where e.job=?");
  // query.setParameter(0, "CLERK");//?是从0开始的
  Query query =session.createQuery("from Emp e where e.job=:job");
  query.setParameter("job", "CLERK");
  List<Emp> list =query.list();
  for(Emp emp:list){
    System.out.println(emp.getEmpno()+"-->"+emp.getEname());
  }
  tx.commit();
  session.close();
}
public void test8(){ //where条件 重要
  Session session = HibUtil.getSession();
  Transaction tx =session.beginTransaction();
  Query query =session.createQuery("from Emp e where e.dept.deptno=:deptno");
  query.setParameter("deptno", 10);
  List<Emp> list =query.list();
  for(Emp emp:list){
    System.out.println(emp.getEmpno()+"-->"+emp.getEname()+"-->"+emp.getDept().getDname());
  }
  tx.commit();
  session.close();
}
public void test9(){ //where条件 重要
  Session session = HibUtil.getSession();
  Transaction tx =session.beginTransaction();
  Query query =session.createQuery("from Emp e left outer join e.dept"); //hql会自动匹配e.deptno=dept.deptno
  query.list();
  tx.commit();
  session.close();
}
public void test10(){ //where条件 重要
  Session session = HibUtil.getSession();
  Transaction tx =session.beginTransaction();
  SQLQuery sqlQuery=session.createSQLQuery("select * from Emp e where e.ename like ?");
  sqlQuery.setParameter(0, "%A%");
  sqlQuery.addEntity(Emp.class);
  List<Emp> empList = sqlQuery.list();
  for(Emp emp:empList){
    System.out.println(emp.getEmpno()+"-->"+emp.getEname()+"-->"+emp.getDept().getDname());
  }
  tx.commit();
  session.close();
}