PHP论坛怎么来实现积分系统

CREATE TABLE `bbs`.`user` (
    `id` INT(10) UNSIGNED NOT NULL COMMENT 'UID' ,
    `avatar` VARCHAR(255) NOT NULL COMMENT '头像' ,
    `nickname` VARCHAR(60) NOT NULL COMMENT '昵称' ,
    `username` VARCHAR(16) NOT NULL COMMENT '用户名' ,
    `password` CHAR(32) NOT NULL COMMENT '密码' ,
    `points` INT(10) NOT NULL DEFAULT '0' COMMENT '积分' ,
    PRIMARY KEY (`id`)
) ENGINE = MyISAM;

CREATE TABLE `bbs`.`level` (
    `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT COMMENT 'ID'
    , `name` VARCHAR(60) NOT NULL COMMENT '等级名' ,
    `top_points` INT(10) UNSIGNED NOT NULL COMMENT '上限积分' ,
    `down_points` INT(10) UNSIGNED NOT NULL COMMENT '下限积分' ,
    PRIMARY KEY (`id`)
) ENGINE = MyISAM;