what are the 12 codd's rule

 

What are the twelve codd’s rule

 

Codd’s rules are a set of guidelines and principels that define the characteristics that define the characteristics that relational database management system (RDBMS) must meet to be considered a truly rlational database. Here are the 12 Codd’s Rules:

 

Rule 0: The Foundation Rule

A relational DBMS must be able to mange its data entirely trough its relational capabilities.

Rule 1: Information rule

All data in a relational database is to be represented in one and only one way, namely by values in tables.

Rule 2: Guaranteed Access Rule

Each and every data element (atomic value) is guaranteed to be accessible logically with a combination of table name, primary key value, and column name.

Rule 3: systematic Treatment of Null values

Null value are treated uniformly and systematically.

Rule 4: Dynamic online catalog Based on the Relational model

The database schema must be stored in the same relational format as regular data.

Rule 5: Comprehensive data sublanguage Rule

A relational data base management system must support at least one well defined language that is capable of providing support for data definition, data manipulation, and data control operations.

Rule 6: View Updating Rule

Views(virtual tables) can be updated just as if they were tables themselves.

Rule 7: High-level Insert,Update, and Delete Rule

The capability of handling a set of records, or a tuple, at once, rather than one at a time.

Rule 8: Physical Data Independence

The application program and terminal must remain logically unimpaired Whenever any changes are made in the storage representation or access methods.

Rule 9: Logical Data Independence

Modifications to the logical scheme must not require changes to the application programs that access the data.

Rule 10: Integrity Independence

Integrity constraints must be specified separetly from application programs and stored in the catalog.

Rule 11: Distribution Independence

The distribution of portions of the databse to various locations should be transparent to users of the system.