日期：3月30日

今天学习时间2.5小时

今天完成的事情：

师兄交代的事情

不太理解抽这个东西，我只能理解为把一样的代码给删了，减少复杂程度，我写了三个代码，也不知道师兄要求的是哪一种。。或者都不是！

（一）statement型

package my;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

public class Demo7 {

static Connection conn;

static Statement stmt;

static ResultSet rs;

static String Driver="com.mysql.jdbc.Driver";

static String url="jdbc:mysql://127.0.0.1:3306/test?useSSL=true";

static String username="root";

static String password="ll..123";

static void select(){

try {

stmt=conn.createStatement();

rs=stmt.executeQuery("select * from tb_test");

while(rs.next()) {

String ID=rs.getString(1);

String name=rs.getString(2);

String QQ=rs.getString(3);

String province=rs.getString(4);

System.out.println("ID="+ID+" 姓名："+name+" QQ:"+QQ+" 省份："+province);

}

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

static void insert(){

try{

stmt=conn.createStatement();

int i;

i=stmt.executeUpdate("insert into tb_test values (3,\"野鸡\",456465,\"湖南\")");

System.out.println("有"+i+"行被改变");

}catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

static void delete() {

try{

stmt=conn.createStatement();

int i;

i=stmt.executeUpdate("delete from tb_test where ID=3");

System.out.println("有"+i+"行被改变");

}catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

static void update() {

try{

stmt=conn.createStatement();

int i;

i=stmt.executeUpdate("update tb_test set name=\"小强\" where ID=1");

System.out.println("有"+i+"行被改变");

}catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

static void create() {

try{

stmt=conn.createStatement();

stmt.executeUpdate("create table tb_demo (ID int not null primary key, name varchar(20),date varchar(20))");

stmt.executeUpdate("insert into tb_demo values (1,\"野鸡\",\"hunan\")");

rs=stmt.executeQuery("select * from tb_demo");

while(rs.next()){

String ID=rs.getString(1);

String name=rs.getString(2);

String date=rs.getString(3);

System.out.println("ID="+ID+" 姓名："+name+" QQ:"+date);

}

}catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

public static void main(String[] args) {

try {

Class.forName(Driver);

conn=DriverManager.getConnection(url,username,password);

// create();

// insert();

// delete();

// update();

select();

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}finally {

if(rs!=null) {

try {

rs.close();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

if(stmt!=null) {

try {

stmt.close();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

if(conn!=null) {

try {

conn.close();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

}

（二）statement型

package my;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.sql.Statement;

public class Demo9 {

public static Connection conn;

public static Statement stmt;

public static ResultSet rs;

public static String Driver="com.mysql.jdbc.Driver";

public static String url="jdbc:mysql://127.0.0.1:3306/test?useSSL=true";

public static String username="root";

public static String password="ll..123";

static void s() {

try {//查找

stmt=conn.createStatement();

rs=stmt.executeQuery("select * from tb_test");

while(rs.next()) {

String ID=rs.getString(1);

String name=rs.getString(2);

String QQ=rs.getString(3);

String province=rs.getString(4);

System.out.println("ID="+ID+" 姓名："+name+" QQ:"+QQ+" 省份："+province);

}

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

/* try{//插入

stmt=conn.createStatement();

int i;

i=stmt.executeUpdate("insert into tb_test values (3,\"野鸡\",456465,\"湖南\")");

System.out.println("有"+i+"行被改变");

}catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

try{//删除

stmt=conn.createStatement();

int i;

i=stmt.executeUpdate("delete from tb_test where ID=3");

System.out.println("有"+i+"行被改变");

}catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

try{//更新

stmt=conn.createStatement();

int i;

i=stmt.executeUpdate("update tb_test set name=\"小强\" where ID=1");

System.out.println("有"+i+"行被改变");

}catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

try{//建表

stmt=conn.createStatement();

stmt.executeUpdate("create table tb_demo (ID int not null primary key, name varchar(20),date varchar(20))");

stmt.executeUpdate("insert into tb_demo values (1,\"野鸡\",\"hunan\")");

rs=stmt.executeQuery("select * from tb_demo");

while(rs.next()){

String ID=rs.getString(1);

String name=rs.getString(2);

String date=rs.getString(3);

System.out.println("ID="+ID+" 姓名："+name+" QQ:"+date);

}

}catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}*/

}

public static void main(String[] args) {

try {

Class.forName(Driver);

conn=DriverManager.getConnection(url,username,password);

s();

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}finally {

if(rs!=null) {

try {

rs.close();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

if(stmt!=null) {

try {

stmt.close();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

if(conn!=null) {

try {

conn.close();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

}

}

（三）preparestatement类型的

package my;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

public class Demo8 {

static String Driver="com.mysql.jdbc.Driver";

static String url="jdbc:mysql://127.0.0.1:3306/test?useSSL=true";

static String username="root";

static String password="ll..123"; 

static Connection conn;

static PreparedStatement sql;

static ResultSet rs;

static void ps() {

try {

sql=conn.prepareStatement("select * from tb_test");

rs=sql.executeQuery();

while(rs.next()) {

String ID=rs.getString(1);

String name=rs.getString(2);

String QQ=rs.getString(3);

String province=rs.getString(4);

System.out.println("ID="+ID+" 姓名："+name+"   QQ:"+QQ+" 省份："+province);

}

// sql=conn.prepareStatement("insert into tb_test values (?,?,?,?)");

// sql.setInt(1, 3);

// sql.setString(2, "阿云");

// sql.setInt(3,4561679);

// sql.setString(4, "河南");

// sql.executeUpdate();

// sql=conn.prepareStatement("delete from tb_test where ID=?");

// sql.setInt(1, 3);

// sql.executeUpdate();

// sql=conn.prepareStatement("update tb_test set name=? where ID=?");

// sql.setString(1, "小明");

// sql.setString(2, "2");

// sql.executeUpdate();

System.out.println("-------------------我是分割线---------------------");

sql=conn.prepareStatement("select * from tb_test");

rs=sql.executeQuery();

while(rs.next()) {

String ID=rs.getString(1);

String name=rs.getString(2);

String QQ=rs.getString(3);

String province=rs.getString(4);

System.out.println("ID="+ID+" 姓名："+name+"   QQ:"+QQ+" 省份："+province);

}

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

public static void main(String[] args) {

try {

Class.forName(Driver);

conn=DriverManager.getConnection(url,username,password);

ps();

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}finally {

if(rs!=null)

try {

rs.close();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

if(sql!=null) {

try {

sql.close();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

if(conn!=null) {

try {

conn.close();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

}

明天计划的事情：

任务1.17接着做！

遇到的问题：暂时没问题，不过在完成任务的过程中需要补充的知识点还在很多，希望以后再线下学习的时候，能把需要用到的知识点都补上来。

收获：编写代码可以有很多种代码达到相同的目的，需要融入个人风格！