-- 创建通知表
CREATE TABLE IF NOT EXISTS `ai_notifications` (
  `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT COMMENT '通知ID',
  `user_id` BIGINT UNSIGNED NOT NULL COMMENT '用户ID',
  `type` VARCHAR(50) NOT NULL COMMENT '通知类型: system(系统通知), learning(学习提醒), achievement(成就通知)',
  `title` VARCHAR(255) NOT NULL COMMENT '通知标题',
  `content` TEXT NOT NULL COMMENT '通知内容',
  `link` VARCHAR(500) DEFAULT NULL COMMENT '跳转链接',
  `is_read` TINYINT(1) NOT NULL DEFAULT 0 COMMENT '是否已读: 0-未读, 1-已读',
  `priority` TINYINT(1) NOT NULL DEFAULT 0 COMMENT '优先级: 0-普通, 1-重要, 2-紧急',
  `created_at` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
  `read_at` TIMESTAMP NULL DEFAULT NULL COMMENT '阅读时间',
  `deleted_at` TIMESTAMP NULL DEFAULT NULL COMMENT '删除时间',
  PRIMARY KEY (`id`),
  KEY `idx_user_id` (`user_id`),
  KEY `idx_is_read` (`is_read`),
  KEY `idx_created_at` (`created_at`),
  KEY `idx_type` (`type`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci COMMENT='通知表';