20175223 MySQL

時間 2019-11-12

標籤 mysql 欄目 MySQL 简体版

原文原文鏈接

目錄html

目錄java

完成結果

要求 1 ：導入world.sql

下載附件中的world.sql.zip, 參考http://www.cnblogs.com/rocedu/p/6371315.html#SECDB，導入world.sql,提交導入成功截圖mysql

截圖：

要求 2 ：CityWanna.java

編寫程序，查詢世界上超過「你學號前邊七位並把最後一位家到最高位，最高位爲0時置1」（好比學號20165201，超過3016520；學號20165208，超過1016520）的全部城市列表，提交運行結果截圖。sql

截圖：

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;
        }
        //輸入學號20175223得：5017522
        //magicNumber[] 替換魔法值
        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(); -> 向數據庫發送SQL查詢語句
            sql = con.createStatement();
            //ResultSet rs = sql.executeQuery(sqlStr); -> 處理查詢結果
            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);
            }
            //馬上關閉鏈接
            con.close();
        } catch (SQLException e) {
            System.out.println("Error:" + e);
        }
    }
}

要求 3 ：CountryWanna.java

編寫程序，查詢世界上的全部中東國家的總人口。數據庫

截圖：

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

編寫程序，查詢世界上的平均壽命最長和最短的國家。url

截圖：

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() 跳讀取下一行信息
             * 如有，返回true，繼續循環
             * 若無，返回false，中止循環
             */
            while (rs.next()) {
                float life = rs.getInt(2);
                String name;
                //獲取第一條數據的信息
                rs.first();
                while (life == 0) {
                    //獲取下一條數據的信息
                    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));
                //獲取最後一條數據的信息
                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);
        }
    }
}

過程當中問題及解決

1. XAMPP沒法啓用 MySQL 程序。

問題 1 解決方法：
在安裝xampp以前電腦上裝過mysql，而後默認啓動的是之前的mysql。
修改註冊表：[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MySQL] 的 ImagePath 修改爲新的xampp中位置 <xampp>\mysql\bin\mysqld MySQL 。

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