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
- photoelectric current sensor
- photoelectric detection
- photoelectric digital sunshine recorder
- photoelectric diode
- photoelectric direct reading spectrometer
- photo electric effect
- photo-electric effect
- photoelectric effect
- photoelectric emission
- photoelectric equation
- photoelectric Fourier analysis
- photoelectric functional material
- photoelectric guidance
- photoelectric guider
- photoelectric guiding
- photoelectric guiding telescope
- photoelectric image tube
- photoelectric imaging microscope
- photoelectric infrared detector materials
- photoelectric instrument
- photoelectric ionization
- photoelectricity
- photoelectricity current transformer
- photoelectricity voltage transformer
- photoelectric light curve