Home » RDBMS

Codd's Rules for RDBMS

RDBMS Codd's Rules: In this tutorial, we are going to learn about the 12 rules proposed by E.F. Codd to define what is required from a database management system in order for it to be considered relational, i.e., a relational database management system.
Submitted by IncludeHelp, on November 08, 2020

Rule Zero

In order for a device to qualify as an RDBMS, this rule states that it must be able to handle the database entirely through relational capabilities.

Rule 1) Information Rule

The value of a table cell must be the data stored in a relational model.

Rule 2) Guaranteed Access Rule

Each element of the data must be accessible by the name of the table, its primary key, and the name of the attribute to be determined by its value.

Rule 3) Systematic treatment of NULL values

NULL values in the database must lead to incomplete, uncertain or invalid values only.

Rule 4) Dynamic Online Catalog

The database layout must be maintained in an online catalogue that can be searched for by registered users.

Rule 5) Comprehensive Data Sub-language Rule

A language supported for description, manipulation and transaction processing operations should be accessible to a database.

Rule 6) View Updating Rule

The framework should automatically update different views that have been generated for different purposes.

Rule 7) High Level Insert, Update and Delete Rule

At each relationship level, the Relational Model should support insert, delete, update, etc. operations. Set operations such as Union, Intersection and minus should also be endorsed.

Rule 8) Physical data independence

Any alteration in the physical position of a table does not involve adjustment at the level of the application.

Rule 9) Logical data independence

Any change to a table 's logical or conceptual schema does not involve modification at the application level. Merging two tables into one, for example, does not impact access to the application, which is difficult to do.

Rule 10) Integrity Independence

Changed integrity restrictions at the database level do not impose changes at the application level.

Rule 11) Distribution Independence

The distribution of data across different locations should not be accessible to end-users.

Rule 12) Non-Subversion Law

In order to alter data, low level access to data should not be able to circumvent the integrity rule.