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RSS订阅翻译 数据库系统概论——Relational Model
Three elements of logical data model(LDM): 逻辑数据模型三要素Data structure 数据结构Data operation 数据操纵Data constraints 数据约束Relational Model is the most popular LDM. 关系数据模型是最常见的数据模型。Typical relational databases: 典...
2018-06-23 20:41:15
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翻译 数据库系统概论——ER Model Constraints
ER Model ConstraintsConstraints:A constraint = an assertion about the database that must be true at all times约束=数据库中任何时间都为真的断言Part of the database schema 数据库模式的一部分Very important in database designComm...
2018-06-23 19:24:02
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翻译 数据库系统概论——data model
Model is the abstraction of real world.模型是真实世界的抽象。reveal the essence of objects, help people to locate and resolve problemsData Modelexplicitly determines the structure of data, and defines the operat...
2018-06-23 18:05:24
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翻译 数据库系统概论——introduction
Database ConceptInformationis any kind of event that affects the state of a dynamic system.is the message (utterance or expression) being conveyedis an ordered sequence of symbols that can be interpre...
2018-06-23 16:45:43
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