【CRUD】

        CRUD是指在做计算处理时的增加、查询（重新得到数据）、更新和删除几个单词的首字母简写。主要被用在描述软件系统中数据库或者持久层的基本操作功能。

        In computing, CRUD is an acronym for create, retrieve, update, and delete. It is used to refer to the basic functions of a database or persistence layer in a software system. 

           C reate    new records
           R etrieve existing records 
           U pdate   existing recordst
           D elete    existing records.