数据库系统基础教程第四章习题解析

Database systems are essential tools for organizing and managing large amounts of data efficiently. In chapter four of the "Database System Fundamentals Tutorial," several important concepts and solutions are discussed. In section 4.1.1, the concept of relationships between entities in a database is introduced. The relationship between entities can be one-to-one, one-to-many, or many-to-many. In the given solutions, various scenarios are provided to explain the different types of relationships, such as a phone and address belonging to a single customer or a phone existing at only one address. These scenarios help in understanding the complexities of database design and management. In section 4.1.2, the concept of weak entities is discussed. A weak entity is an entity that cannot exist without the presence of another related entity. In the solutions provided, the key ssNo of customers is identified as part of the composite key of the entity set in scenarios where the relationships are m-to-n, indicating a weak entity. Understanding weak entities is crucial in database design to ensure data integrity and efficient data retrieval. Overall, chapter four of the "Database System Fundamentals Tutorial" provides valuable insights into the complexities of database design, relationships between entities, and the concept of weak entities. By studying and implementing the solutions provided in the chapter, database administrators and developers can enhance their skills in database management and optimization.