What are the 12 Codd rules of RDBMS
In the previous blog, we installed Oracle. In this blog, we will learn What are the 12 Codd Rules of RDBMS. These rules define the structure of a RDBMS. Building blocks of RDBMS are based on these rules.
RDBMS Stands for Relational Database Management System. It is based on the relational model proposed by E. F. Codd in 1970’s.
Codd rules, also called Codd’s 12 rules were proposed by Dr. E.F. Codd. These rules should be satisfied for a database system to be considered as a relational model.
All popular RDBMS such MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access follow the Codd principles.
Codd’s 12 rules for RDBMS
Rule 1 : The information rule. All information in the database should be represented in the same way, and stored in tables in the form of rows and columns.
Rule 2 : The guaranteed access rule. All data must be accessible logically using the table name, primary key (identifying the row) and column (attribute value).
Rule 3 : Systematic treatment of null values. The Null values in a database should be handled systematically and uniformly.
Rule 4 : Active online catalog. The structure of the entire database must be stored in an online catalog, as a data dictionary. This data dictionary can be queried by users employing the same query language as used to query other tables in the database.
Rule 5 : The comprehensive data sub language rule. The system must support at least one relational language that 1. Has a linear syntax 2. Can be used both interactively and within application programs 3. Supports data definition operations, data manipulation operations, security and integrity constraints, and transaction management operations. This rule necessitates a query language like SQL.
Rule 6 : The view updating rule. All views that can be updated theoretically, must be updated by the system.
Rule 7 : High-level insert, update, and delete. The system must support insert, update, and delete operations on the database. It should also support operators that manipulate a set of rows instead of just a single row.
Rule 8 : Physical data independence. Data stored in the database should be independent of how it is being accessed by external applications.
Rule 9 : Logical data independence. Any changes in the logical data should not impact the applications using it.
Rule 10 : Integrity independence. Integrity constraints must stay separate from the application using it. These constraints must be specified separately and cataloged. They can be modified as needed without affecting the application.
Rule 11 : Distribution independence. The distribution of data to different servers and locations should be hidden from the user. The user should not get impacted by the distribution of data.
Rule 12: The non-subversion rule. The database system access should never bypass a relational security or integrity constraint.
Next: Basics of RDBMS