【JDBC之CURD-install/update/delete小练习】

╰半夏微凉° 2023-10-02 18:56 8阅读 0赞

1.在db3数据库插入一条记录  
使用try\{\}catch\{\}抛异常  
注册驱动,  
ip地址为127.0.0.1,数据库:db3,用户名:root,密码:1234  
获取Connection对象  
定义sql语句  
获取statement对象  
执行sql语句  
处理结果  
判断是否成功  
释放资源

public static void main(String[] args) {
        
            Connection conn = null;
            Statement stat = null;
            try {
        
                //1.创建连接
                Class.forName("com.mysql.jdbc.Driver");
                //2.创建connection对象
                conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "1234");//本机ip端口号可以省略不写
                //3.创建statement对象
                stat = conn.createStatement();
                //4.定义sql插入语句
                String sql = "insert into account(ID,NAME, BALANCE) value (NULL,'wangwu',1000);";//id为主键自增长,所以可以null
    
                //5.执行sql语句
                int index = stat.executeUpdate(sql);
                //6.输出结果
                System.out.println(index);
                if (index > 0) {
        
                    System.out.println("录入成功!");
                } else {
        
                    System.out.println("输入有误!");
                }
            } catch (ClassNotFoundException e) {
        
                e.printStackTrace();
            } catch (SQLException throwables) {
        
                throwables.printStackTrace();
            } finally {
        
                //7.释放资源
                if (stat != null) {
        
                    try {
        
                        stat.close();
                    } catch (SQLException throwables) {
        
                        throwables.printStackTrace();
                    }
                    if (conn != null) {
        
                        try {
        
                            stat.close();
                        } catch (SQLException throwables) {
        
                            throwables.printStackTrace();
                        }
                    }
                }
            }
        }

2.将db3数据库中account表字段balance所有值改为1000  
使用try\{\}catch\{\}抛异常  
注册驱动,  
ip地址为127.0.0.1,数据库:db3,用户名:root,密码:1234  
获取Connection对象  
定义sql语句  
获取statement对象  
执行sql语句  
处理结果  
判断是否成功  
释放资源

public static void main(String[] args) {
        
            Connection conn = null;
            Statement stat = null;
            try {
        
                //注册驱动
                Class.forName("com.mysql.jdbc.Driver");
                //获取Connection对象
                conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/db3", "root", "1234");
                //定义sql语句
                String sql = "update account set balance =1000 ;";
                //获取Statement对象
                stat = conn.createStatement();
                //执行sql
                int index = stat.executeUpdate(sql);//受影响行数
                //处理结果
                System.out.println(index);
                //判断是否执行成功并给予用户提示
                if (index > 0) {
        
                    System.out.println("录入成功!");
                } else {
        
                    System.out.println("请检查录入代码是否有错误!");
                }
            } catch (ClassNotFoundException e) {
        
                e.printStackTrace();
            } catch (SQLException throwables) {
        
                throwables.printStackTrace();
            } finally {
        
                //释放资源,避免空指针异常
                if(stat!=null){
        //判断sql语句是否为空
                    try {
        
                        stat.close();
                    } catch (SQLException throwables) {
        
                        throwables.printStackTrace();
                    }
                }
                if(conn!=null){
        //判断conn是否为空
                    try {
        
                        stat.close();
                    } catch (SQLException throwables) {
        
                        throwables.printStackTrace();
                    }
                }
    
            }
    
    
        }

3.在account表中删除字段name=wangwu的所有记录;  
使用try\{\}catch\{\}抛异常  
注册驱动,  
ip地址为127.0.0.1,数据库:db3,用户名:root,密码:1234  
获取Connection对象  
定义sql语句  
获取statement对象  
执行sql语句  
处理结果  
判断是否成功  
是否资源

public static void main(String[] args) {
        
            Connection conn=null;
            Statement stat=null;
            try {
        
                //1.导入驱动包
                Class.forName("com.mysql.jdbc.Driver");
                //2.获取Connection
                conn = DriverManager.getConnection("jdbc:mysql:///db3", "root", "1234");
                //3.获取statement对象
                stat = conn.createStatement();
                //4.定义sql语句
                String sql="delete from account where name='wangwu';";//删除account表中字段你name=wangwu的所有记录
                //5.执行sql语句
                int index = stat.executeUpdate(sql);
                //6.输出结果
                System.out.println(index);
                if(index>0){
        
                    System.out.println("执行成功");
                }else{
        
                    System.out.println("sql代码书写有误");
                }
            } catch (ClassNotFoundException e) {
        
                e.printStackTrace();
            } catch (SQLException throwables) {
        
                throwables.printStackTrace();
            }finally{
        
                //释放资源
                try {
        
                    stat.close();
                } catch (SQLException throwables) {
        
                    throwables.printStackTrace();
                }
                try {
        
                    conn.close();
                } catch (SQLException throwables) {
        
                    throwables.printStackTrace();
                }
            }
        }