用Jdbc连接数据库后实现增删改查功能

增删改用的都是executeUpdate（）方法；
查用的是executeQuery（）方法
package cn.lideng.dbc;

import java.lang.management.ManagementFactory;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

public class jdbcdemo3 {

    private static Statement statement;
    private static Connection connection;

    public static void main(String[] args) {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/qy97", "root", "root");
            String sql="delete from users where sid=2";
            statement = connection.createStatement();
            int i = statement.executeUpdate(sql);
            System.out.println(i);
            if(i>0){
                System.out.println("删除成功");
            }
            else{
                System.out.println("修改成功");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            if(statement!=null){
                try {
                    statement.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
            if(connection!=null){
                try {
                    connection.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}




package cn.lideng.dbc;

import JdbcUtils.JdbcUtilsDemo;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

public class JdbcDemo4 {

    private static Connection connection;
    private static Statement statement;
    private static ResultSet rs;

    public static void main(String[] args) {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/qy97", "root", "root");
            String  sql="select * from users";
            statement = connection.createStatement();
            rs = statement.executeQuery(sql);
            while(rs.next()){
                int id = rs.getInt(1);
                String name = rs.getString(2);
                String address= rs.getString(3);

                System.out.println(id+"   "+name+"   "+address);
            }
            
        } catch (Exception e) {
            e.printStackTrace();
        }finally {
            JdbcUtilsDemo.close(rs,statement,connection);
        }
    }
}