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Notice: Undefined index: HTTPS in /www/wwwroot/mengmianren.com/wp-content/plugins/dessky-cache/dessky-cache.php on line 43 :查询插入修改删除A、查询B、插入C、修改D、删除数据操作描述了关系模型的动态特性,规定了可以在关系上执行的操作 – 萌面人博客