20175223 MySQL

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。

目录

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 。