求翻译：在系统中主要实现的功能可分为以下几类，一是教师发布课题，二是学生选题，三是教研室主任对课题进行查看审批，四是系主任对课题进行查看审批。在本系统的具体实现中，即编码阶段，除了综合面向对象的开发技术外，SQL语句是贯穿整个程序的，无论是查询、删除、插入、修改用SQL语句实现都是比较直观的，而且易懂。是什么意思？

The functionality is mainly implemented in the system can be divided into the following categories, one teacher release topic, students topics, the Department Director on a topic to view it for approval, the Head of the Department for approval subject to see. The concrete realization of this system,