20175223 MySQL

目录

目录

• 完成结果
  • 要求 1 ：导入world.sql
  • 要求 2 ：CityWanna.java
    • CityWanna.java
  • 要求 3 ：CountryWanna.java
    • CountryWanna.java
  • 要求 4 ：LifeWanna.java
    • LifeWanna.java
• 过程中问题及解决
  • 1. XAMPP无法启用 MySQL 程序。

完成结果

要求 1 ：导入world.sql

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

• 截图：
  
  

要求 2 ：CityWanna.java

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。

• 截图：
  
  

CityWanna.java

import java.sql.*;
import java.util.Scanner;
/**
 * @author 10542
 */
public class CityWanna {
    public static void main(String[] args) throws SQLException {
        Connection con;
        Statement sql;
        ResultSet rs;
        String url = "jdbc:mysql://localhost:3306/world";
        String user = "root";
        String password = "";
        con = DriverManager.getConnection(url, user,password);
        if (con == null) {
            return;
        }
        //输入学号20175223得：5017522
        //magicNumber[] 替换魔法值
        int [] magicNumber = new int[]{10,1000000};
        int studentId ,frist ,last;
        System.out.println ("Input your student's id:");
        Scanner reader = new Scanner (System.in);
        studentId = reader.nextInt ();
        frist = studentId/10;
        last = studentId%10;
        frist = frist + last*1000000;
        if (frist/magicNumber[1]==magicNumber[0]) {
            frist=(frist-10000000)+1000000;
        }
        else if (frist/magicNumber[1]>magicNumber[0]) {
            frist=frist-10000000;
        }
        System.out.println ("Result:" +frist);
        try {
            //Statement sql = con.createStatement(); -> 向数据库发送SQL查询语句
            sql = con.createStatement();
            //ResultSet rs = sql.executeQuery(sqlStr); -> 处理查询结果
            rs = sql.executeQuery("select*from city where population>"+Integer.toString (frist));
            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);
            }
            //立刻关闭连接
            con.close();
        } catch (SQLException e) {
            System.out.println("Error:" + e);
        }
    }
}

要求 3 ：CountryWanna.java

编写程序，查询世界上的所有中东国家的总人口。

• 截图：
  
  

CountryWanna.java

import java.sql.*;
/**
 * @author 10542
 */
public class CountryWanna {
    public static void main(String[] args) throws SQLException {
        Connection con;
        Statement sql;
        ResultSet rs;
        String uri = "jdbc:mysql://localhost:3306/world";
        String user = "root";
        String password = "";
        con = DriverManager.getConnection(uri, user,password);
        if (con == null) {
            return;
        }
        try {
            sql = con.createStatement();
            rs = sql.executeQuery("select Name,Population from country where Region = 'Middle East'");
            int allPopulation = 0;
            while (rs.next()) {
                String name = rs.getString(1);
                int population = rs.getInt(2);
                System.out.printf("The population of %s is %d\n", name, population);
                allPopulation = allPopulation + population;
            }
            System.out.println("The population of Middle East" + allPopulation);
        } catch (SQLException e) {
            System.out.println("Error:" + e);
        }

    }
}

要求 4 ：LifeWanna.java

编写程序，查询世界上的平均寿命最长和最短的国家。

• 截图：
  
  

LifeWanna.java

import java.sql.*;
/**
 * @author 10542
 */
public class LifeWanna {
    public static void main(String[] args) throws SQLException {
        Connection con;
        Statement sql;
        ResultSet rs;
        String uri = "jdbc:mysql://localhost:3306/world";
        String user = "root";
        String password = "";
        con = DriverManager.getConnection(uri, user,password);
        if (con == null) {
            return;
        }
        try {
            sql = con.createStatement();
            rs = sql.executeQuery("select Name,LifeExpectancy from country order by LifeExpectancy");
            /**
             * rs.next() 跳读取下一行信息
             * 若有，返回true，继续循环
             * 若无，返回false，停止循环
             */
            while (rs.next()) {
                float life = rs.getInt(2);
                String name;
                //获取第一条数据的信息
                rs.first();
                while (life == 0) {
                    //获取下一条数据的信息
                    rs.next();
                    life = rs.getInt(2);
                }
                name = rs.getString(1);
                System.out.println("The shortest life expectancy in the world:" + name);
                System.out.println ("LifeExpectancy is:" + rs.getInt (2));
                //获取最后一条数据的信息
                rs.last();
                name = rs.getString(1);
                System.out.println("The longest life expectancy in the world:" + name);
                System.out.println ("LifeExpectancy is:" + rs.getInt (2));

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

过程中问题及解决

1. XAMPP无法启用 MySQL 程序。

• 问题 1 解决方法：
  
  在安装xampp之前电脑上装过mysql，然后默认启动的是以前的mysql。
  
  修改注册表：[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MySQL] 的 ImagePath 修改成新的xampp中位置 <xampp>\mysql\bin\mysqld MySQL 。