理学 数据库系统 释 relational algebra 关系代数 一种抽象的关系数据语言，它通过对关系的运算来表达查询。
algebra of relations 关系代数 relation algebra 关系代数 relational algebra 关系代数 relationship algebra 关系代数
数据库 数据库理论 释文 relational algebra 关系代数
- metal phthalocyanine
- metal physical evidence
- metal physics
- metal pipe
- metal pipeline detector
- metal plastic
- metal plate and strip
- metal plating
- metal poisoning
- metal-poor binary
- metal-poor cluster
- metal-poor dwarf
- metal-poor giant
- metal-poor globular cluster
- metal-poor object
- metal-poor star
- metal porphyrin mimic enzymes
- metal positive
- metal powder
- metal products printing
- metal ratio
- metal reduction
- metal reduction process
- metal reflectance film
- metal reflective electrode