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。
relational algebra 关系代数
数据库 数据库理论 释文 relational algebra 关系代数
- BD星表
- BD真空
- BE
- Be
- BEA
- Beach Bathing Place
- beach land management
- beach nourishment
- beach placer
- beach profile measurement
- beach protection works
- beach ridge
- beachrock
- beach seine fishing
- beach seining through boat deployment
- beach soccer
- beach towel
- beach volleyball
- beach volleyball court
- beach volleyball of Summer Deaflympics
- beachwear
- beacon
- beacon differential positioning
- beacon fire
- beacon frame