Summary and Highlights: Designing Keys, Indexes, and Constraints总结与要点：键、索引与约束设计

Congratulations! You have completed this lesson. At this point, you know that:
祝贺您完成了本课程。此时，您已经知道：

• An instance serves as both a logical and configuration boundary within a relational database system.
  实例在关系数据库系统中既充当逻辑边界，也充当配置边界。
• A relational database comprises related objects used for storing, managing, and accessing data organized within schemas.
  关系数据库由用于存储、管理和访问数据的相关对象组成，这些数据组织在模式中。
• Schemas logically group various database objects like tables, views, functions, and triggers, with user schemas containing user-defined objects and system schemas containing configuration and metadata.
  模式将各种数据库对象（如表、视图、函数和触发器）逻辑分组，用户模式包含用户定义的对象，系统模式包含配置和元数据。
• Large tables can be partitioned across multiple partitions to optimize performance.
  大型表可以被划分到多个分区中以优化性能。
• Database objects encompass the items existing within the database, including tables, views, and functions.
  数据库对象包括数据库中存在的项目，包括表、视图和函数。
• Primary keys enforce the uniqueness of rows in tables, while foreign keys establish relationships between tables.
  主键确保表中行的唯一性，而外键建立表之间的关系。
• Indexes, essential for optimizing database performance, are data structures facilitating quick retrieval of specific rows based on certain criteria.
  索引是优化数据库性能的关键数据结构，它们通过特定标准快速检索特定行。
• Indexing involves storing pointers to rows in a table, aiding the SQL processor in swiftly locating requested data.
  索引涉及存储指向表中行的指针，帮助 SQL 处理器快速定位所需数据。
• Indexes should be created judiciously, balancing advantages against potential disadvantages.
  索引的创建应审慎进行，权衡其优势与潜在劣势。
• Normalization, including first (1NF), second (2NF), and third (3NF) normal forms, reduces redundancy and enhances data consistency by organizing data logically.
  规范化，包括第一范式（1NF）、第二范式（2NF）和第三范式（3NF），通过逻辑组织数据来减少冗余并增强数据一致性。
• Entity integrity constraints ensure the uniqueness of primary key values, while referential integrity constraints specify table relationships.
  实体完整性约束确保主键值的唯一性，而参照完整性约束指定表之间的关系。
• Semantic integrity constraints maintain the correctness of data meaning, and domain constraints enforce valid attribute values.
  语义完整性约束维护数据的正确性，而域约束强制执行有效的属性值。
• Null constraints mandate non-null attribute values, and check constraints restrict accepted attribute values.
  空值约束要求非空属性值，而检查约束限制接受的属性值。