Hibernate常用的聚合函数

左手的ㄟ右手 2024-02-17 15:34 13阅读 0赞

package entity;  
//持久化类  
import javax.persistence.Entity;  
import javax.persistence.GeneratedValue;  
import javax.persistence.GenerationType;  
import javax.persistence.Id;  
import javax.persistence.Table;

//HQl查询图书信息  
@Entity  
@Table  
public class HqlQuery \{  
private int id;  
private String name;  
private String author;  
@Id  
@GeneratedValue(strategy=GenerationType.IDENTITY)  
public int getId() \{  
return id;  
\}  
public void setId(int id) \{  
this.id = id;  
\}  
public String getName() \{  
return name;  
\}  
public void setName(String name) \{  
this.name = name;  
\}  
public String getAuthor() \{  
return author;  
\}  
public void setAuthor(String author) \{  
this.author = author;  
\}  
  
public HqlQuery() \{  
super();  
\}  
public HqlQuery(String name, String author) \{  
super();  
this.name = name;  
this.author = author;  
\}  
\}

//五大函数：

package test;

import org.hibernate.Session;  
import org.hibernate.Transaction;

import util.HibernateUtil;

public class FunTest \{

public static void main(String\[\] args) \{  
//hcount();  
//hsum();  
//hmax();  
//hmin();  
havg();  
\}  
public static void hcount()\{  
Session session=HibernateUtil.getCurrentSession();  
Transaction transaction=session.beginTransaction();  
String hql="select count(\*) from HqlQuery";  
long n=(Long) session.createQuery(hql).uniqueResult();  
System.out.println("记录数：" + n);  
\}  
public static void hsum()\{  
Session session=HibernateUtil.getCurrentSession();  
Transaction transaction=session.beginTransaction();  
String hql="select sum(id) from HqlQuery";  
long n=(Long) session.createQuery(hql).uniqueResult();  
System.out.println("和为：" + n);  
\}  
public static void hmax()\{  
Session session=HibernateUtil.getCurrentSession();  
Transaction transaction=session.beginTransaction();  
String hql="select max(id) from HqlQuery";  
int n=(Integer) session.createQuery(hql).uniqueResult();  
System.out.println("最大id：" + n);  
\}  
public static void hmin()\{  
Session session=HibernateUtil.getCurrentSession();  
Transaction transaction=session.beginTransaction();  
String hql="select min(id) from HqlQuery";  
int n=(Integer) session.createQuery(hql).uniqueResult();  
System.out.println("最小id：" + n);  
\}  
public static void havg()\{  
Session session=HibernateUtil.getCurrentSession();  
Transaction transaction=session.beginTransaction();  
String hql="select avg(id) from HqlQuery";  
double n=(Double) session.createQuery(hql).uniqueResult();  
System.out.println("id平均值为：" + n);  
\}  
\}