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);

        }

    }

}