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JDBC增（预编译方式）

public static void main(String[] args) throws Exception {
    //配置信息
    //useUnicode=true&characterEncoding=utf-8解决中文乱码问题
    String url = "jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8";
    String username="root";
    String password="123456";
    //1.加载驱动
    Class.forName("com.mysql.jdbc.Driver");

    //2.连接数据库,代表数据库
    Connection connection = DriverManager.getConnection(url, username, password);

    //3.编写SQL
    String sql="insert into users(id, name, password, email, birthday) values (?,?,?,?,?);";

    //4.预编译
    PreparedStatement preparedStatement = connection.prepareStatement(sql);
    preparedStatement.setInt(1,5);//给第一个占位符？的值赋值为4
    preparedStatement.setString(2,"坤士南山1 ");//给第二个占位符？的值赋值为坤士南山
    preparedStatement.setString(3,"12314");//给第三个占位符？的值赋值为12314
    preparedStatement.setString(4,"44@qq.com");//给第四个占位符？的值赋值为44@qq.com
    preparedStatement.setDate(5,new Date(new java.util.Date().getTime()));//给第五个占位符？的值赋值为new Date(new java.util.Date().getTime())

    //5.执行SQL
    int i = preparedStatement.executeUpdate();
    if(i>0){
        System.out.println("插入成功");
    }

    //6.关闭资源，释放资源（一定要做） 先开后关

    preparedStatement.close();
    connection.close();
}

JDBC删（预编译方式）

public static void main(String[] args) throws ClassNotFoundException, SQLException {
    //配置信息
    //useUnicode=true&characterEncoding=utf-8解决中文乱码问题
    String url = "jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8";
    String username="root";
    String password="123456";
    //1.加载驱动
    Class.forName("com.mysql.jdbc.Driver");

    //2.连接数据库,代表数据库
    Connection connection = DriverManager.getConnection(url, username, password);

    //3.编写SQL
    String sql="delete from users where id =?;";

    //4.预编译
    PreparedStatement preparedStatement = connection.prepareStatement(sql);
    preparedStatement.setString(1,"4 ");

    //5.执行删除SQL 返回的i是受影响的行数  增删改都是用executeUpdate
    int i = preparedStatement.executeUpdate();
    if(i>0){
        System.out.println("执行成功");
    }else{
        System.out.println("执行失败");
    }

    //6.关闭资源，释放资源（一定要做） 先开后关
    preparedStatement.close();
    connection.close();
}

JDBC改(预编译方式)

public static void main(String[] args) throws ClassNotFoundException, SQLException {
    //配置信息
    //useUnicode=true&characterEncoding=utf-8解决中文乱码问题
    String url = "jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8";
    String username="root";
    String password="123456";
    //1.加载驱动
    Class.forName("com.mysql.jdbc.Driver");

    //2.连接数据库,代表数据库
    Connection connection = DriverManager.getConnection(url, username, password);

    //3.编写SQL
    String sql="update users set name = ?,password = ?,email = ?,birthday = ? where id = ?;";

    //4.预编译
    PreparedStatement preparedStatement = connection.prepareStatement(sql);

    preparedStatement.setString(1,"坤士南山 ");//给第二个占位符？的值赋值为坤士南山
    preparedStatement.setString(2,"12314");//给第三个占位符？的值赋值为12314
    preparedStatement.setString(3,"ns@qq.com");//给第四个占位符？的值赋值为44@qq.com
    preparedStatement.setDate(4,new Date(new java.util.Date().getTime()));//给第五个占位符
    preparedStatement.setInt(5,4);//给第一个占位符？的值赋值为4
    //5.执行删除SQL 返回的i是受影响的行数  增删改都是用executeUpdate
    int i = preparedStatement.executeUpdate();
    if(i>0){
        System.out.println("执行成功");
    }else{
        System.out.println("执行失败");
    }

    //6.关闭资源，释放资源（一定要做） 先开后关
    preparedStatement.close();
    connection.close();
}

JDBC查

public static void main(String[] args) throws ClassNotFoundException, SQLException {
    //配置信息
    //useUnicode=true&characterEncoding=utf-8解决中文乱码问题
    String url = "jdbc:mysql://localhost:3306/jdbc?useUnicode=true&characterEncoding=utf-8";
    String username="root";
    String password="123456";
    //1.加载驱动
    Class.forName("com.mysql.jdbc.Driver");

    //2.连接数据库,代表数据库
    Connection connection = DriverManager.getConnection(url, username, password);

    //3.向数据库发送SQL的对象Statement:CRUD
    Statement statement = connection.createStatement();

    //4.编写SQL
    String sql="select * from users";

    //5.执行查询SQL，返回一个ResultSet 结果集
    ResultSet rs = statement.executeQuery(sql);
    while (rs.next()){
        System.out.println("id"+rs.getObject("id"));
        System.out.println("name"+rs.getObject("name"));
        System.out.println("password"+rs.getObject("password"));
        System.out.println("email"+rs.getObject("email"));
        System.out.println("birthday"+rs.getObject("birthday"));

    }

    //6.关闭资源，释放资源（一定要做） 先开后关
    rs.close();
    statement.close();
    connection.close();
}