HQL语法

 

import java.util.List;

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

import com.utils.HibernateUtils;

//学习HQL语法
public class HqlDemo {
	
	public static void main(String[] args) {
		fun1();
		//fun2();
		//fun3();
		//fun4();
		//fun5();
	}
	
	//基本语法
	public static void fun1(){
		Session session = HibernateUtils.openSession();
		Transaction tx = session.beginTransaction();
		
		String hql = "from com.pojo.Customer ";//完整写法
		String hql2 = "from Customer "; //简单写法
		String hql3 = "from java.lang.Object "; 
		
		Query query = session.createQuery(hql3);
		
		List list = query.list();
		
		System.out.println(list);

		tx.commit();
		session.close();
		
	}
	
	
	//排序
	public static void fun2(){
		Session session = HibernateUtils.openSession();
		Transaction tx = session.beginTransaction();
		
		String hql1 = "from com.pojo.Customer order by cust_id asc";//完整写法
		String hql2 = "from com.pojo.Customer order by cust_id desc";//完整写法
		
		Query query = session.createQuery(hql2);
		
		List list = query.list();
		
		System.out.println(list);
		
		tx.commit();
		session.close();
		
	}

	//条件查询
	public static void fun3(){
		Session session = HibernateUtils.openSession();
		Transaction tx = session.beginTransaction();
		
		String hql1 = "from com.pojo.Customer where cust_id =?";//完整写法
		String hql2 = "from com.pojo.Customer where cust_id = :id";//完整写法
		
		Query query = session.createQuery(hql2);
		
//		query.setParameter(0, 2l);
		query.setParameter("id", 2l);
		
		
		List list = query.list();
		
		System.out.println(list);
		
		tx.commit();
		session.close();
		
	}
	
	//分页查询
	public static void fun4(){
		Session session = HibernateUtils.openSession();
		Transaction tx = session.beginTransaction();
		
		String hql1 = "from com.pojo.Customer";//完整写法
		
		Query query = session.createQuery(hql1);
		
		//limit ?,?
		// (当前页数-1)*每页条数
		query.setFirstResult(2);
		query.setMaxResults(2);
		
		List list = query.list();
		
		System.out.println(list);
		
		tx.commit();
		session.close();
		
	}
	
	//聚合函数查询
	public static void fun5(){
		Session session = HibernateUtils.openSession();
		Transaction tx = session.beginTransaction();
		
		String hql1 = "select count(*) from  com.pojo.Customer  ";//完整写法
		String hql2 = "select sum(cust_id) from com.pojo.Customer";//完整写法
		String hql3 = "select avg(cust_id) from com.pojo.Customer";//完整写法
		String hql4 = "select max(cust_id) from com.pojo.Customer";//完整写法
		String hql5 = "select min(cust_id) from com.pojo.Customer";//完整写法
		
		Query query = session.createQuery(hql5);
		
		Number number  = (Number) query.uniqueResult();
		
		System.out.println(number);
		
		tx.commit();
		session.close();
		
	}
	
	
	//投影查询
	public static void fun6(){
		Session session = HibernateUtils.openSession();
		Transaction tx = session.beginTransaction();
		
		String hql1 = "select cust_name from com.pojo.Customer";
		String hql2 = "select cust_name,cust_id from com.pojo.Customer";
		String hql3 = "select new Customer(cust_id,cust_name) from com.pojo.Customer";
		
		Query query = session.createQuery(hql3);
		
		List list = query.list();
		
		System.out.println(list);
		
		
		tx.commit();
		session.close();
		
	}
}