In database design, composite keys uniquely identify records and prevent duplication. However, wide multi-column keys can increase index size, comparison work, and join costs. Surrogate keys can mitigate some of these costs, but they also require additional constraints and governance to preserve business-level uniqueness. This paper presents a Reversible Numeric Composite Key (RNCK): a single non-negative integer that encodes multiple normalized attributes and can be decoded back to the original tuple under a fixed schema. RNCK is designed to combine the semantic fidelity of composite keys with the operational convenience of numeric keys. RNCK can improve storage footprint and key-comparison efficiency when attribute domains are bounded and stable. We formalize correctness and ordering properties, and specify operational semantics for partial-overflow mode. The approach has been used in production systems and is applicable to relational databases, static datasets, and key-value caching systems within the stated constraints.

翻译：在数据库设计中，复合键能够唯一标识记录并防止重复。然而，宽泛的多列键会增加索引大小、比较开销和连接成本。代理键可以减轻部分成本，但需要额外的约束和管控来保证业务层面的唯一性。本文提出了一种可逆数值复合键（Reversible Numeric Composite Key, RNCK）：一个能够编码多个规范化属性、并在固定模式下可解码回原始元组的单一非负整数。RNCK旨在结合复合键的语义保真度与数值键的操作便捷性。当属性域有界且稳定时，RNCK能改善存储空间占用和键比较效率。我们形式化描述了其正确性与排序性质，并明确了部分溢出模式下的操作语义。该方法已在生产系统中得到应用，适用于在给定约束条件下的关系数据库、静态数据集和键值缓存系统。