预处理对象，增删改查

package com.orcal.demo001;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Scanner;

public class Demo01 {
    //删除数据
public static void main(String[] args) throws ClassNotFoundException, SQLException {
    Scanner sc=new Scanner(System.in);
    System.out.println("请输入删除的姓名：");
    String name=sc.next();
    Class.forName("com.mysql.jdbc.Driver");
    String url="jdbc:mysql://localhost:3306/shop?characterEncoding=utf8";
    String uname="root";
    String ped="123456";
    Connection co=DriverManager.getConnection(url,uname,ped);
    String sql="delete from user where uname=?";
    PreparedStatement jie=co.prepareStatement(sql);
    jie.setString(1, name);
    int i=jie.executeUpdate();
    co.close();
    jie.close();
}
}

package com.orcal.demo001;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Scanner;
//修改数据
public class Demo02 {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
    
    Class.forName("com.mysql.jdbc.Driver");
    String url="jdbc:mysql://localhost:3306/shop?characterEncoding=utf8";
    String uname="root";
    String ped="123456"; 
    Connection co=DriverManager.getConnection(url,uname,ped);
    String sql="update user set uname=? where pwd=?";
    PreparedStatement feng=co.prepareStatement(sql);
    feng.setString(1, "xiaoxiao");//给第一个问好赋值
    feng.setInt(2, 111);
    int aa=feng.executeUpdate();
    System.out.println(aa);
    feng.close();
    co.close();
    
}
}

package com.orcal.demo001;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Scanner;

public class Demo04 {
    //添加数据
public static void main(String[] args) throws ClassNotFoundException , SQLException{
    
        System.out.println("请输入用户名");
        Scanner sc=new Scanner(System.in);
        String name=sc.next();
        System.out.println("密码");
        String password=sc.next();
        
    
    Class.forName("com.mysql.jdbc.Driver");
    String url="jdbc:mysql://localhost:3306/shop?characterEncoding=utf8";
    String uname="root";
    String ped="123456";
    Connection conn=DriverManager.getConnection(url, uname,ped);//连接对象
    String sql="insert into user(uname,pwd) values(?,?) ";
    PreparedStatement pst=conn.prepareStatement(sql);
    pst.setString(1, name);
    pst.setString(2, password);
    
    int rs=pst.executeUpdate();
    
    
    pst.close();
    conn.close();//先开的后关
}
}

package com.orcal.demo001;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Scanner;

public class DemoLianxi {
public static void main(String[] args) throws ClassNotFoundException, SQLException {
    
    Class.forName("com.mysql.jdbc.Driver");
    String url="jdbc:mysql://localhost:3306/shop?characterEncoding=utf8";
    String uname="root";
    String ped="123456"; 
    //增
    /*Connection co=DriverManager.getConnection(url,uname,ped);
    String sql="insert into user(uname,pwd) values(?,?)";
    PreparedStatement tian=co.prepareStatement(sql);
    tian.setString(1, "小红");
    tian.setInt(2, 123);
    int s=tian.executeUpdate();
    System.out.println(s);
    tian.close();
    co.close();*/
    //删
    /*Connection co=DriverManager.getConnection(url, uname, ped);
    String sql="delete from user where uname=?";
    PreparedStatement stat=co.prepareStatement(sql);
    stat.setString(1, "小红");
    int a=stat.executeUpdate();
    System.out.println(a);
    stat.close();
    co.close();*/
    //改
    /*Connection co=DriverManager.getConnection(url,uname,ped);
    String sql="update user set uname=? where pwd=?";
    PreparedStatement sta=co.prepareStatement(sql);
    
    sta.setString(1, "dada");
    sta.setInt(2, 999);
    int a=sta.executeUpdate();
    System.out.println(a);
    sta.close();
    co.close();*/
    //查
    Connection co=DriverManager.getConnection(url,uname,ped);
    String sql="Select * from user where uname=?";
    PreparedStatement sta=co.prepareStatement(sql);
    sta.setString(1, "xiaoxiao");
    ResultSet aa=sta.executeQuery();
    while(aa.next()){
        String a=aa.getString("uid");
        String b=aa.getString("uname");
        String c=aa.getString("pwd");
        System.out.println(a+b+c);
    }
    aa.close();
    sta.close();
    co.close();
    /*Connection co=DriverManager.getConnection(url,uname,ped);
    String sql="select * from user where pwd=?";
    PreparedStatement sta=co.prepareStatement(sql);
    sta.setInt(1, 111);
    ResultSet rs=sta.executeQuery();
    
    while(rs.next()){
        String uid=rs.getString("uid");
        String uname1=rs.getString("uname");
        String pwd=rs.getString("pwd");
                System.out.println(uid+uname+pwd);
    }
    rs.close();
    sta.close();
    co.close();
    */
    
    
}
}