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relational calculus

强调
微软 реляционная алгебра (In database management, a nonprocedural method for manipulating relations (tables). There are two families of relational calculus: domain calculus and tuple calculus. The two families of relational calculus are mathematically equivalent to each other and to relational algebra. Using either family, one can formulate a description of a desired relation, based on the existing relations in the database)
技术 реляционное исчисление; исчисление отношений
电子产品 реляционное исчисление