JDBC练习_update、DDL语句和JDBC各个类详解_ResultSet_基本使用

JDBC练习_delete、DDL语句

    /*
         account表 删除一条记录
     */
    private static void delete() {
        Connection conn = null;
        Statement stat = null;
        try {
            //注册驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            //获取Connection对象
            conn = DriverManager.getConnection("jdbc:mysql:///db2", "root", "root");
            //定义sql
            String sql = "delete from account where id = 3";
            //获取执行sql的对象 Statement
            stat = conn.createStatement();
            //执行sql
            int i = stat.executeUpdate(sql);
            //处理结果
            System.out.println(i);
            if (i>0){
                System.out.println("删除成功");
            }else {
                System.out.println("删除失败");
            }

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            if (stat!=null){
                try {
                    stat.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
            if (conn!=null){
                try {
                    conn.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        }
    }

 

 

 

 

 

 

    /*
        创建一张student表
     */
    private static void DDL() {
        Connection conn = null;
        Statement stat = null;
        try {
            //注册驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            //获取Connection对象
            conn = DriverManager.getConnection("jdbc:mysql:///db2", "root", "root");
            //定义sql
            String sql = "create table student (id int, name varchar(20))";
            //获取执行sql的对象 Statement
            stat = conn.createStatement();
            //执行sql
            int i = stat.executeUpdate(sql);
            //处理结果
            System.out.println(i);
            
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            if (stat!=null){
                try {
                    stat.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
            if (conn!=null){
                try {
                    conn.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        }
    }

 

 

 

 

JDBC各个类详解_ResultSet_基本使用

ResultSet：结果集对象，封装查询结果

　　next() ：游标向下移动一行

　　getXxx(参数)：获取数据

　　　　Xxx：代表数据类型 如：int getInt()，String getString()

　　　　参数：

　　　　　　1.int：代表列的编号，从1开始  如：getString(1)

　　　　　　2.String : 代表列名称。如：getDouble("balance")

    private static void ResultSet() {
        Connection conn = null;
        Statement stat = null;
        ResultSet rs = null;
        try {
            //注册驱动
            Class.forName("com.mysql.cj.jdbc.Driver");
            //获取Connection对象
            conn = DriverManager.getConnection("jdbc:mysql:///db2", "root", "root");
            //定义sql
            String sql = "select * from account";
            //获取执行sql的对象 Statement
            stat = conn.createStatement();
            //执行sql
            rs = stat.executeQuery(sql);
            //处理结果
            //让游标向上移动一行
            rs.next();
            //获取数据
            int id = rs.getInt(1);
            String name = rs.getString("name");
            double balance = rs.getDouble(3);

            System.out.println(id+"-"+name+"-"+balance);

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }finally {
            if (rs!=null){
                try {
                    rs.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }

            if (stat!=null){
                try {
                    stat.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
            if (conn!=null){
                try {
                    conn.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        }
    }

 

 

搜索

复制