正常化 [英] Normalisation
问题描述
你好朋友，
请为任何idia贡献;
两种普通形式之间有什么区别（1NF，2NF）
Hi freinds,
pls contribute any idia on;
what is the difference between two normal forms (1NF,2NF)
推荐答案
你好朋友，
请提供任何idia;
两种普通形式之间有什么区别（1NF，2NF）
Hi freinds,
pls contribute any idia on;
what is the difference between two normal forms (1NF,2NF)
普通形式有许多等价的定义。这是一个版本：
1NF
每个表必须有一个主键，即一个可以唯一标识记录的最小属性集。必须有原子性，即每个属性必须包含一个值，而不是一组值。通过定义键控和非键控属性，不应该有重复组（在不同记录上似乎需要不同次数的数据类别）适当。
2NF
数据库必须满足1NF的所有要求。此外，如果表具有复合键，则所有属性必须与整个键相关。并且，在表的多行中冗余复制的数据应该移出到单独的表中。
There are many equivalent definitions for normal forms. Here is a version:
1NF
Each table must have a primary key, i.e., a minimal set of attributes that can uniquely identify a record.There must be atomicity i.e each attribute must contain a single value, not a set of values.There should be no repeating groups (categories of data that would seem to be required a different number of times on different records) by defining keyed and non-keyed attributes appropriately.
2NF
The database must meet all the requirements of the 1NF. In addition, if a table has a composite key, all attributes must be related to the whole key. And, data that is redundantly duplicated across multiple rows of a table should be moved out to a separate table.
你好朋友，
请给出任何idia;
两种普通形式之间有什么区别（1NF，2NF）
Hi freinds,
pls contribute any idia on;
what is the difference between two normal forms (1NF,2NF)
Alem
查看以下内容
Mary
First Normal表格
- 消除各个表中的重复组。
- 为每组相关数据创建单独的表
- 使用主键识别每组相关数据
- 为适用于多条记录的值集创建单独的表
- 使用外键关联这些表
Alem，在一个礼仪点，我注意到你用你的用户名（Alem）标题所有线程。如果你能让你的主题标题简要描述你所遇到的问题，对所有相关的人来说会更好。
这也会让董事会的专家更倾向于拥有看看你的主题。
Alem, on a point of board etiquette, I notice that you title all of the threads you start with your user name (Alem). It would be better for all concerned if you could make your thread titles an short description of the problem you are having.
It will also make the experts on the board more inclined to have a look at your threads.
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