三、JDBC——Statement

Statement

statement语句是SQL语句的描述，使用它可以操作各种SQL语句，包括DDL（数据定义语句，如创建表）、DML（CRUD）和DCL等。

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1、在src中的com包下创建Test2.java

package com; import java.sql.SQLException; import com.mysql.jdbc.Connection; import com.mysql.jdbc.Statement; public class Test2 { public static void main(String []args){ // CreateTbale(); // Insert(); // Update(); // Delete(); } static void Delete(){ Connection connection=DBUtil.open(); String sqlString="delete from User where id>0 &&id<9"; try { Statement statement=(Statement)connection.createStatement(); statement.executeUpdate(sqlString); } catch (Exception e) { // TODO: handle exception }finally{ DBUtil.close(connection); } } //更新 static void Update(){ Connection conn=DBUtil.open(); String sql="update User set name='big cxg' where id>3"; try { Statement statement=(Statement) conn.createStatement(); statement.executeUpdate(sql); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ DBUtil.close(conn); } } //增加数据 static void Insert(){ Connection conn=DBUtil.open(); String sql="insert into User(name,email)values('cxg','cxg@qq.com')"; try { Statement statement=(Statement) conn.createStatement(); statement.executeUpdate(sql); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ DBUtil.close(conn); } } //创建表 static void CreateTbale(){ Connection conn=DBUtil.open(); String sql="create table User(id int primary key auto_increment,name varchar(20),email varchar(20))"; try { Statement statement=(Statement) conn.createStatement(); statement.execute(sql); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } finally{ DBUtil.close(conn); } } }

2、DBUtil.java作为连接数据库

package com; import java.io.FileNotFoundException; import java.io.FileReader; import java.io.Reader; import java.sql.DriverManager; import java.sql.SQLException; import java.util.Properties; import com.mysql.jdbc.Connection; public class DBUtil { //定义成不可修改的 private static String driver; private static String url; private static String username; private static String password; //把值都按要求填入 static { //获取配置文件的内容 Properties p=new Properties(); Reader reader; try { reader = new FileReader("src//config.properties");//配置文件路径 p.load(reader);//加载驱动文件 } catch (Exception e) { e.printStackTrace(); } driver=p.getProperty("driver"); url=p.getProperty("url"); username=p.getProperty("username"); password=p.getProperty("password"); } //打开数据库 public static Connection open() { try { //注册加载驱动 Class.forName(driver); //链接数据库 return (Connection) DriverManager.getConnection(url,username,password); } catch (Exception e) { e.printStackTrace(); } return null; } //关闭数据库 public static void close(Connection conn) { if(conn!=null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } }