Codd's Rules in RDBMS System

 Codd's 12 Rules in RDBMS System

The Computer Scientist Name- E.F. Codd (Edgar Frank Ted Codd) who invented the Rules for Relational Database Model on the behalf of these rules any DBMS system are Called either RDBMS or Not. There are Total 13 rules but due to its first rule i.e. zero (0), We call Codd's 12 Rules.

These rules followed by DBMS system and if more than 6 rules are followed by any DBMS System than these DBMS systems are called RDBMS (Relational Database Management System) systems. Relational Database created based on Relational Model must follow the codd's 12 rules.

Codd's Proposed these 12 rules to show the quality required in DBMS to become it as RDBMS System. If these 13 rules are followed by any DBMS system than this system has highest quality of RDBMS but eventually there is no any kind of DBMS which follows all the Rules. Even the RDBMS system we are using called Oracle only follows 8 or 8.5 rules out of 13. Let us understand what are rules defined by E.F. Codd for DBMS System.

Codd's 12 Rules

Codd's 12 Rules in RDBMS System

Rule Zero- Foundation Rule:-

This rule states that the RDBMS system must manage the Database Completely using its relational capabilities. It means DBMS system is qualified as RDBMS if it follows this rule by using relational capabilities whole database is managed.

This rule is called fundamental rule because the remaining rules are based on this rule.

Rule 1- Information Representation Rule:-

This Rule illustrate that the Information must be stored in well representative manner. It means all the information stored in RDBMS system inside cells of a table. The Information including metadata is stored in Logical Level in cells of a table.

Rule 2- Guaranteed Access-  

This Rule illustrate that fetching of data will be possible at any time by giving the Table Name, Column Name and Primary Key. It means data must be available when Table Name, Column Name and Primary key is used.

Rule 3- Systematic Treatment of NULL Values-

This Rule illustrate about proper management of NULL values. The Null value must be distinct from 0  or empty string. The Null value will be used where the value is not provided or missing data or not applicable value. Null value must be represented by NULL not by 0 or empty string or by any other number. Primary key must contain NOT NULL value. So NULL value treatment is required in RDBMS System.

Rule 4- Active Online Catalog-   

This Rule illustrate about the Database description or information of Database structure will be stored online in Catalog. The Catalog is nothing but the Database Dictionary where all the structural information of Database is stored. The Catalog can be accessed by Authorized user. User can access the Data Dictionary or Catalog by same query as the query used to access other Database objects.

Rule 5- The Comprehensive Data Sub-Language Rule-

This Rule says that the Database must provide support for the languages which follow the linear syntax and have the ability to perform Data Definition, Data Manipulation, Data Control and Transaction Controlling operations. The Database must be accessed by these language either by directly or by using any third party applications. Point to be noted here if it is possible to manipulate the Database without using these supportive language than this is the violation of this rule.

Rule 6- View Updating Rule-

This Rule illustrate about the view concept of Database and states that if all the views in database updated theoretically than it also updated in Database System at system level.

Rule 7- High-Level Insert, Update and Delete Rule- 

This states that there should be high level support for Insert, Delete and Update Relational Queries. RDBMS also support the Set operations like Union, Minus and Intersection.

 

Rule 8- Physical Data Independence-

This rule says that the physical storage should not create any problem to system when the supporting table for a file is renamed or moved to other disk.

Rule 9- Logical Data Independence-

This rule illustrate that if any changes done at logical level( structure of Table) than there is no problem at the view level. It means if we have a view of a table and we want to split that table into two tables then there will be a new view which will be showing the same result by merging these splitted tables.

Rule 10- Integrity Independence-  

This rule states that RDBMS should have the ability to enforce its own integrity using own programs rather than other programs. There are Primary key, Foreign key, Not Null, Unique, Check, Trigger constraints are stored in Catalog or Data Dictionary. It means by using integrity, RDBMS system independent at front End.

Rule 11- Distribution Independence-   

This rule says that the Database distribution on Network (like Geographically) should not create any problem and it should work properly to user so that user feel like the data is stored at single location.

Rule-12- Non-Subversion Rule-

This Rule states that if any lower level programming or procedure is allowed or exist than it should not  bypass or unable to bypass the integrity rules provided by the RDBMS System on Database.