Cord's 12 Rules.

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1. Information Rule
2. Guaranteed Access Rule
3. Systematic Treatment of Null Values 
4. Dynamic online Catalog based on relational model
5. Comprehensive data sub language 
6. View updating Rule
7. High level insert, delete, update Rule
8. Physical data independent
9. Logical data independent 
10. Integrity independence 
11. Distribution independence 
12. Non-sub version Rule

  •  Information Rule : All the data should be maintain in form of row and column at atomic level.
  • Guaranteed Access Rule:  Since data is stored in atomic level and exactly in one format so access is gauranteed.
  •  Systematic Treatment of Null Values : All missing value must be stored exactly in one format that is null.
  •  Dynamic online Catalog based on relational model :As the database get maintain offline, it must be maintained online also.
  • Comprehensive data sub language : Different sub language for different query DLL, DML, DQL, DTL.
  • View updating Rule : As database is updatable, it must be  updatable through view also.
  • High level insert, delete, update Rule : Database must have high level queries such as insert, delete and so on.
  • Physical data independent : The physical data level must be independent from another.
  • Logical data independent :Logical level must be independent from another.
  •  Integrity independence : Integrity means Correctness in data, All the integrity rules define must be independent of each other.
  • Distribution independence : The distribution data along various location should not be visible to users.
  • Non-sub version Rule : Data has been stored at lowest level so integrity constraints specify for the data can not be bypassed.

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