《数据库MySQL(课下作业，必做)》第十周作业 20175301

一、任务详情

1. 下载附件中的world.sql.zip, 参考http://www.cnblogs.com/rocedu/p/6371315.html#SECDB，导入world.sql,提交导入成功截图
2. 编写程序，查询世界上超过“你学号前边七位并把最后一位家到最高位，最高位为0时置1”（比如学号20165201，超过3016520；学号20165208，超过1016520）的所有城市列表，提交运行结果截图
3. 编写程序，查询世界上的所有中东国家的总人口
4. 编写程序，查询世界上的平均寿命最长和最短的国

二、作业步骤

1.1安装xampp

1.2导入world sql（PHP管理器）

2.1我的学号为20175301，改为3017530
编写程序，在最高位置1

import java.sql.*;

public classConnectionDemo1 {
    public static void main(String[] args) {
        Connection con;
        Statement sql;
        ResultSet rs;
        con = GetDBConnection.connectDB("world", "root", "");
        if (con == null) {
            return;
        }
        String sqlStr = "select*from city where population>3017530";
        try {
            sql = con.createStatement();
            rs = sql.executeQuery(sqlStr);
            while (rs.next()) {
                int id = rs.getInt(1);
                String name = rs.getString(2);
                String countryCode = rs.getString(3);
                String district = rs.getString(4);
                int population = rs.getInt(5);
                System.out.printf("%d\t", id);
                System.out.printf("%s\t", name);
                System.out.printf("%s\t", countryCode);
                System.out.printf("%s\t", district);
                System.out.printf("%d\n", population);
            }
            con.close();
        } catch (SQLException e) {
            System.out.println("Error:" + e);
        }


    }
}

3
查询世界上的所有中东国家的总人口

import java.sql.*;

public class ConnectionDemo {
    public static void main(String[] args) {
        Connection con;
        Statement sql;
        ResultSet rs;
        con = GetDBConnection.connectDB("world", "root", "  ");
        if (con == null) {
            return;
        }
        try {
            sql = con.createStatement();
            rs = sql.executeQuery("select Name,Population from country where Region = 'Middle East'");
            int all = 0;
            while (rs.next()) {
                String name = rs.getString(1);
                int population = rs.getInt(2);
                System.out.printf("%s国家的人口为%d\n", name, population);
                all += population;
            }
            System.out.println("中东国家的总人口为：" + all);
        } catch (SQLException e) {
            System.out.println("Error:" + e);
        }

    }
}

4
查询世界上的平均寿命最长和最短的国家
有的国家平均寿命没有，所以需要加一个无的判断

import java.sql.*;

public class ConnectionDemo {
    public static void main(String[] args) {
        Connection con;
        Statement sql;
        ResultSet rs;
        con = GetDBConnection.connectDB("world", "root", " ");
        if (con == null) {
            return;
        }
        try {
            sql = con.createStatement();
            rs = sql.executeQuery("select Name,LifeExpectancy from country order by LifeExpectancy");
            while (rs.next())![](https://img2018.cnblogs.com/blog/1268747/201905/1268747-20190503153351189-916996880.jpg)


            {
                float num = rs.getInt(2);
                String name = rs.getString(1);

                while (num == 0)
                {
                    rs.next();
                    num = rs.getInt(2);
                }
                name = rs.getString(1);
                System.out.println("平均寿命最短的国家为：" + name);
                rs.last();
                name = rs.getString(1);
                System.out.println("平均寿命最长的国家为：" + name);
            }
        }

        catch (SQLException e) {
            System.out.println("Error:" + e);
        }

    }
}

三、码云链接

https://gitee.com/ShengHuoZaiDaXue/20175301/tree/master/20175301/20175301