HQL基础查询语句

HQL基础查询语句

1.使用hql语句检索出Student表中的所有列

//核心代码
@Test
public void oneTest()
{
  Query query=session.createQuery("form Student");
  List<Student> list=query.list();
  for(Student item:list)
 {
   System.out.println(item.getName());
 } 

}

2.使用hql语句语句检索出部分列

//核心代码
@Test
public void twoTest()
{
  Query query=session.createQuery("select name from Student");
  List<String> list=query.list();
  for(String item:list)
 {
   System.out.println(item);
 }
}

3.使用hql语句检索出多列

//核心代码
@Test
public void threeTest()
{
  Query query=session.createQuery("select name,age from Student");
  List<Object[]> list=query.list();
  for(Object[] item : list)
 {
   System.out.println(item[0]+"\t"+item[1]);
 }
}

4.投影出多列，有构造植入，返回强类型

//核心代码
@Test
public void fourTest()
{
   Query query=session.createQuery("select Student(id,name,age) from Student");//Student(id,name,age)和实体类带参构造顺序相同
   List<Student> list=query.list();
   for(Student item:list)
  {
     System.out.println(item.getName());
  }
}

5.带条件查询，匿名占位符

//核心代码
@Test
public void fiveTest()
{
  Query query=session.createQuery("select Student from Student where name=?");
  query.setParameter(0,"王小三");
  List<Student> list=query.list();
  for(Student item:list)
 {
   System.out.println(item.getName());
 }
}

6.带条件查询，名称占位符

//核心代码
@Test
    public void SixTest()
    {
        Query query = session.createQuery("select Student from Student where stu.sname=:name");
        query.setParameter("name", "王小四");
        List<Student> list=query.list();
        for (Student item : list) {
            System.out.println(item.getSid());
        }
    }

7.动态查询，需要新建一个工具类，用到几个属性就封装几个属性

public class StudentCondition {
    private String name;
    private Integer age;
    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

}

//测试类核心代码
StudentCondition condition=new StudentCondition();
        condition.setAge(25);
        condition.setName(null);
        StringBuilder sb=new StringBuilder();
        sb.append("from Student where 1=1 ");
        Student stu=new Student();
        if(condition.getAge()!=null)
        {
            sb.append(" and sage=:sage");
            stu.setSage(condition.getAge());
        }
        if(condition.getName()!=null)
        {
            sb.append(" and sname=:sname");
            stu.setSname(condition.getName());
        }
        Query query = session.createQuery(sb.toString());
        query.setProperties(stu);
        List<Student> list=query.list();
        for (Student item : list) {
            System.out.println(item.getSname());
        }//投影出年龄25岁的学生信息
    }

8.分页查询数据

@Test
    public void nineTest()
    {
        String sql="from Student";
        Query query = session.createQuery(sql);
        Integer pageIndex=1;
        Integer pageSize=2;
        query.setFirstResult((pageIndex-1)*pageSize);
        query.setMaxResults(pageSize);
        List<Student> list = query.list();

        for (Student student : list) {
            System.out.println(student);
        }