数据库系统绪论与模型：概念、架构与技术。

数据库系统是一种用于管理和存储数据的系统，它有助于减少数据冗余和提高数据的一致性。数据库系统和文件系统之间的主要区别在于数据库系统更复杂，能够解决数据冗余和数据独立性等问题，并且能够管理不同类型的数据，适用于不同规模的计算机。数据库系统的三级模式包括外模式、模式和内模式，其中真正存在的是模式。数据模型是信息世界的模型，将现实世界与机器世界联系起来。 数据管理技术经历了记录管理、文件管理和数据库管理三个阶段。实体之间的联. On the topic of databases, it is important to understand the fundamentals of a database system and its role in managing and storing data. Database systems are designed to reduce data redundancy and improve data consistency. The main difference between a database system and a file system lies in the complexity and capabilities of the former. Database systems can solve issues like data redundancy and data independence, manage different types of data, and cater to a range of computer sizes. The three-level schema of a database system consists of the external schema, conceptual schema, and internal schema, with the actual existence being in the conceptual schema. Data modeling serves as a bridge between the real world and the machine world, acting as a model of the information world. Data management technology has evolved through three stages, namely record management, file management, and database management. Entity relationships play a crucial role in establishing connections between different entities within a database. These relationships are vital for maintaining data integrity and ensuring effective data management. Understanding the concepts and principles of database systems is essential for anyone working with data and information management.