hibernate-聚合函数分组统计数据查询

聚合函数：

实例：

package Test;

import static org.junit.Assert.*;

import java.util.List;

import org.hibernate.Session;
import org.junit.Test;

import entity.AvgSal;

import util.HibernateSessionFactory;
import util.HibernateUtil;

public class AggTest {

    /**
     * 统计部门个数。
     */
    @Test
    public void test1() {
        Session session =HibernateSessionFactory.getSession();
        try {
            Long count = (Long) session.createQuery("select count(d) from Dept d").uniqueResult();
            System.out.println("共有"+count+"个部门。");
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }

    /**
     * 统计员工工资。
     */
    @Test
    public void test2() {
        Session session =HibernateSessionFactory.getSession();
        try {
            Double totalsal = (Double) session.createQuery("select sum(e.sal) from Emp e").uniqueResult();
            System.out.println("员工工资总数为："+totalsal);
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }

    /**
     * 统计员工最低工资。
     */
    @Test
    public void test3() {
        Session session =HibernateSessionFactory.getSession();
        try {
            Double minsal = (Double) session.createQuery("select min(e.sal) from Emp e").uniqueResult();
            System.out.println("员工工资最低为："+minsal);
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }

    /**
     * 统计员工最高工资。
     */
    @Test
    public void test4() {
        Session session =HibernateSessionFactory.getSession();
        try {
            Double maxsal = (Double) session.createQuery("select max(e.sal) from Emp e").uniqueResult();
            System.out.println("员工工资最高为："+maxsal);
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }
    /**
     * 统计员工平均工资。
     */
    @Test
    public void test5() {
        Session session =HibernateSessionFactory.getSession();
        try {
            Double avgsal = (Double) session.createQuery("select avg(e.sal) from Emp e").uniqueResult();
            System.out.println("员工平均工资为："+avgsal);
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }
    /**
     * 统计最低工资、最高工资以及平均工资。
     */
    @Test
    public void test6() {
        Session session =HibernateSessionFactory.getSession();
        try {
            List<Object[]> list = session.createQuery("select min(e.sal),max(e.sal),avg(e.sal) from Emp e").list();
            for (Object[] objects : list) {
                Double minsal=(Double) objects[0];
                Double maxsal=(Double) objects[1];
                Double avgsal=(Double) objects[2];
                System.out.println("最低工资为："+minsal+"，最高工资为："+maxsal+",平均工资为："+avgsal);
            }
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }
    /**
     * 统计员工职位个数。
     */
    @Test
    public void test7() {
        Session session =HibernateSessionFactory.getSession();
        try {
            Long jobcount = (Long) session.createQuery("select count(distinct e.job) from Emp e").uniqueResult();
            System.out.println("共有"+jobcount+"种职位");
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }

    /**
     * 按职位统计员工个数。
     */
    @Test
    public void test8() {
        Session session =HibernateSessionFactory.getSession();
        try {
            List<Object[]> list = session.createQuery("select job,count(ename) from Emp group by job").list();
            System.out.println("按职位统计员工个数");
            for (Object[] objects : list) {
                String job=(String) objects[0];
                Long count=(Long) objects[1];
                System.out.println(job+"职位======"+count+"个员工");
            }

        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }

    /**
     * 统计各个部门的平均工资
     */
    @Test
    public void test9() {
        Session session =HibernateSessionFactory.getSession();
        try {
            List<Object[]> list = session.createQuery("select job,avg(sal) from Emp group by job").list();
            System.out.println("按职位统计每个职位员工的平均工资");
            for (Object[] objects : list) {
                String job=(String) objects[0];
                Double avg=(Double) objects[1];
                System.out.println(job+"职位平均工资是======"+avg);
            }

        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }
    /**
     * 统计各个职位的最低工资和最高工资
     */

    @Test
    public void test10() {
        Session session =HibernateSessionFactory.getSession();
        try {
            List<Object[]> list = session.createQuery("select job,max(sal),min(sal) from Emp group by job").list();
            System.out.println("统计各个职位的最低工资和最高工资");
            for (Object[] objects : list) {
                String job=(String) objects[0];
                Double max=(Double) objects[1];
                Double min=(Double) objects[2];
                System.out.println(job+"职位最高工资是======"+max+",最低工资是：===="+min);
            }

        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }

    /**
     * 统计各个部门平均工资高于2000元的部门名称，打印部门名称、部门平均工资
     */
    @Test
    public void test11() {
        Session session =HibernateSessionFactory.getSession();
        try {
            List<Object[]> list = session.createQuery("select dept.dname,avg(sal) from Emp group by dept.dname having avg(sal)>2000").list();
            System.out.println("统计各个部门平均工资高于2000元的部门名称，打印部门名称、部门平均工资");
            for (Object[] objects : list) {
                String dept=(String) objects[0];
                Double avg=(Double) objects[1];
                System.out.println(dept+"\t"+avg);
            }

        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }
    /**
     * 统计各个部门平均工资高于2000元的部门名称，打印部门名称、部门平均工资，使用JavaBean封装查询结果
     */
    @Test
    public void test12() {
        Session session =HibernateSessionFactory.getSession();
        try {
            List<AvgSal> list = session.createQuery("select new entity.AvgSal(dept.dname,avg(sal) )from Emp group by dept.dname having avg(sal)>2000").list();
            System.out.println("统计各个部门平均工资高于2000元的部门名称，打印部门名称、部门平均工资，使用JavaBean(entity.AvgSal)封装查询结果");
            for (AvgSal avgSal : list) {
                System.out.println(avgSal.getDname()+"\t"+avgSal.getAvgsal());
            }

        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("失败");
        }
    }

}