问题
单项选择题
关系数据库中的关系应满足一定的要求，最起码的要求是达到1NF，即满足
A．每个属性都是不可分解的
B．主码属性唯一标识关系中的元组
C．关系中的元组不可重复
D．每个非码属性都完全依赖于主码属性
答案
参考答案：A
解析： 第一范式的定义是：如果关系模式R的每一个属性都是不可分解的，则称R为第一范式。
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关系数据库中的关系应满足一定的要求，最起码的要求是达到1NF，即满足
A．每个属性都是不可分解的
B．主码属性唯一标识关系中的元组
C．关系中的元组不可重复
D．每个非码属性都完全依赖于主码属性
参考答案：A
解析： 第一范式的定义是：如果关系模式R的每一个属性都是不可分解的，则称R为第一范式。
A person’s home is as much a reflection of his personality as the clothes he wears, the food he eats and the friends with whom he spends his time. Depending on personality, most have in mind a(n) “______ home”. But in general, and especially for the student or new wage earners, there are practical ______ of cash and location on achieving that idea. Cash ______, in fact, often means that the only way of ______ when you leave school is to stay at home for a while until things ______ financially. There are obvious ______of living at home—personal laundry is usually ______ done along with the family wash; meals are provided and there will be a well-established circle of friends to ______. And there is ______ the responsibility for paying bills, rates, etc. On the other hand, ______ depends on how a family gets on. Do your parents like your friends? You may love your family—______do you like them? Are you prepared to be ______ when your parents ask where you are going in the evening and what time you expect to be back? If you find that you cannot strike a(n) ______, and that you finally have the money to leave, how do you ______ finding somewhere else to live? If you plan to stay in your home area, the possibilities are ______well-known to you already. Friends and the local paper are always ______. If you are going to work in a ______ area, again there are the papers—and the accommodation agencies, ______ these should be approached with ______. Agencies are allowed to charge a fee, usually the ______ of the first week’s rent, if you take accommodation they have found for you.
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