EFCodd rules for RDBMS

E.F. codd proposed total 13 rules related with RDBMS. On its basis RDBMS is introduced. These rules are as follows –

Rule 0 :-  According to this rule a system is said to be a RDBMS, if that can manage whole data base unavoidably by relational capability. It is also known as foundation rule.

Rule 1 (information rule) :- All informations related with meta data will be represented in form of data which stored in cells of table. Here no fixed order of row and column.

Rule 2 (Guaranted access) :- Every unique value of data (atomic value) can be accessed by name of table+primary key (row)+attribute(column).
NOTE :- Direct accessing via pointer is voilation of this rule.

Rule 3 (Systematic treatment of NULL) :- There are many meanings of NULL. For example, missing data, not NULL, applicable or no value. It should be well organized controlled. In primary key unavoidably NOT NULL should not present and if any expression is NULL then its result should also NULL. Zero or blank space should not entered in place of NULL value.

Rule 4 (Active online catalog) :- Overall statements of data base should be stored by data base dictionary (catalog) and rule of data base should apply on catalog also. Query language should also used in catalog as data base.

Rule 5 (powerful language) :- At least one well defined programming language should be present on it, by which data of whole data base can be accessed.
Example :- SQL

Rule 6 (View updation rule) :- All views must be chnaged in fundamental form and it’s change should be made by system.

Rule 7 (Relation level operation):- Insert, update and delete etc. operations should be done on every level of relation. With it set operation like set union, interesection and minus should be supported by relation.

Rule 8 (Physical data independency) :- There is no effect of change in physical storage on system. It means if name of any file is chnaged which supports table or that is moved from one place to another on memory then no effect of this change on application.

Rule 9 (Logical data independency) :- if any change is made in logical structure (tables) of data base then it shouldn’t effected to user’s view related with that. It means a table is divided into two parts then result of view related with that table will be provided by joining both that tables. It is very difficult task to complete this rule.

Rule 10 (Integrity independency) :- Integrity rules should their own by data base no other program should used for it. Key, check constraints, trigger etc. should be stored in data dictionary, by which data base of RDBMS are independent.

Rule 11 (Distribution in-dependency):- work should be successfully done also on distributed network by a DBMS. This rule shows concept of distribute data base.

Rule 12 (Non sub version rule) :- if low level access is provided in system also then that access cannot bypass integrity rules of data base. This work is done by data inscription or sorting.