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📜  DBMS规范化：1NF，2NF，3NF和BCNF的示例

📅  最后修改于: 2020-12-12 03:01:28             🧑  作者: Mango

正常化

  • 规范化是组织数据库中数据的过程。
  • 归一化用于最小化一个关系或一组关系的冗余。它还可用于消除不希望出现的特征，例如插入，更新和删除异常。
  • 规范化将较大的表划分为较小的表，并使用关系将它们链接起来。
  • 正常形式用于减少数据库表的冗余。

范式的类型

普通形式有四种类型：

Normal Form Description
1NF A relation is in 1NF if it contains an atomic value.
2NF A relation will be in 2NF if it is in 1NF and all non-key attributes are fully functional dependent on the primary key.
3NF A relation will be in 3NF if it is in 2NF and no transition dependency exists.
4NF A relation will be in 4NF if it is in Boyce Codd normal form and has no multi-valued dependency.
5NF A relation is in 5NF if it is in 4NF and not contains any join dependency and joining should be lossless.