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Recovery Recovery Types of Failures Types of Failures Wrong data entry Wrong data entry Prevent by having constraints in the database Fix with data cl 阅读全文
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规范化问题的提出 在规范化理论出现以前，层次和网状数据库的设计只是遵循其模型本身固有的原则，而无具体的理论依据可言，因而带有盲目性，可能在以后的运行和使用中发生许多预想不到的问题。 在规范化理论出现以前，层次和网状数据库的设计只是遵循其模型本身固有的原则，而无具体的理论依据可言，因而带有盲目性，可能 阅读全文
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SQL is a very-high-level language, in which the programmer is able to avoid specifying a lot of data-manipulation details that would be necessary in l 阅读全文
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1.Data Model Model Model Is the abstraction of real world Reveal the essence of objects, help people to locate and resolve problems Is the abstraction 阅读全文
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1.Database concepts (1)Data & Information (1)Data & Information Information Information Is any kind of event that affects the state of a dynamic syste 阅读全文