20175314薛勐 数据库MySQL(课下作业，必做)

数据库MySQL(课下作业，必做)

要求

1. 下载附件中的world.sql.zip, 参考Intellj IDEA 简易教程：数据库，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家

思路

• 比较说明需要用到where 子语句，保证查询的字段值在某个区间内
• 我的学号是20175314，所以应该输出超过6017531的所有城市列表

代码

GetDBConnection.java（启动数据库）

package MySQL;
import java.sql.*;
public class GetDBConnection {
    public static Connection connectDB(String DBName,String id,String p) {
        Connection con = null;
        String
                uri = "jdbc:mysql://localhost:3306/"+DBName+"?serverTimezone=GMT%2B8&characterEncoding=utf-8";
        try{  Class.forName("com.mysql.cj.jdbc.Driver");//加载JDBC-MySQL驱动
        }
        catch(Exception e){}
        try{
            con = DriverManager.getConnection(uri,id,p); //连接代码
        }
        catch(SQLException e){}
        return con;
    }
}

getCity.java

package MySQL;
import java.sql.*;
public class getCity {
    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 * FROM city");
            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);
                if(Population>6017531) {
                    System.out.printf("%d	", ID);
                    System.out.printf("%s	", Name);
                    System.out.printf("%s	", CountryCode);
                    System.out.printf("%s	", District);
                    System.out.printf("%d
", Population);
                }
            }
            con.close();
        }
        catch (SQLException e) {
            System.out.println(e);
        }
    }
}

getPopulation.java

package MySQL;
import java.sql.*;
public class getPopulation {
    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 country where Region = 'Middle East'";
        try {
            sql = con.createStatement();
            rs = sql.executeQuery(sqlStr);
            long totalpopulation = 0;
            while(rs.next()) {
                int Population = rs.getInt(7);
                totalpopulation +=Population;
            }
            System.out.println("中东国家的总人口为"+totalpopulation);
            con.close();
        }
        catch (SQLException e) {
            System.out.println(e);
        }
    }
}

getLife.java

package MySQL;
import java.sql.*;
public class getLife {
    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 country order by LifeExpectancy";
        try {
            sql = con.createStatement();
            rs = sql.executeQuery(sqlStr);
            rs.first();
            String highcountry,lowcountry;
            float number1 = rs.getInt(8);
            while(number1 == 0) {
                rs.next();
                number1 = rs.getInt(8);
            }
            lowcountry = rs.getString(2);
            System.out.println("世界上平均寿命最短的国家为："+lowcountry+" 寿命为"+number1);
            rs.last();
            float number2 = rs.getInt(8);
            highcountry = rs.getString(2);
            System.out.println("世界上平均寿命最长的国家为："+highcountry+" 寿命为"+number2);
            con.close();
        }
        catch (SQLException e) {
            System.out.println(e);
        }
    }
}

测试结果

Navicat Premium 12:world

getCity.java

getPopulation.java

getLife.java

码云链接

参考资料

Intellj IDEA 简易教程：数据库