理学 数据库系统 释 relational calculus 关系演算 一种抽象的关系数据语言，它通过数理逻辑中的谓词演算表达查询的要求。
数据库 数据库理论 释文 relational calculus 关系演算
- Nikki Brown
- Nikki Giovanni
- Nikki S.Lee
- Nikkō Tōshō-gū
- Niklas Luhmann
- Nikodým
- Nikodým boundedness theorem
- Nikodým convergence theorem
- Nikodým metric
- Nikolaas Tinbergen
- Nikolae Grigorescu
- Nikolai Afanassyevich Kryuchkov
- Nikolai Aleksandrovich Menshutkin
- Nikolai Alekseevich Klyuev
- Nikolai Alekseevich Polevoy
- Nikolai Cherkasov
- Nikolai Dmitriyevich Kuznetsov
- Nikolai Frederik Severin Grundtvig
- Nikolai Fyodorovich Pogodin
- Nikolai Fyodorovich Shcherbina
- Nikolai Gerasimovich Pomyalovsky
- Nikolai Ivanovich Lebedev
- Nikolai Ivanovich Nadezhdin
- Nikolai Ivanovich Vavilov
- Nikolai Maksimovich